Application of quantitative prediction to design new organic dyes in dye sensitized solar cells

Accepted Manuscript Application of quantitative prediction to design new organic dyes in dye sensitized solar cells

Kenan Sun, Yue Liu, Yaxu Wu, Xugeng Guo, Junfeng Li, Li Wang PII: DOI: Reference:

S0167-7322(18)36632-7 https://doi.org/10.1016/j.molliq.2019.01.078 MOLLIQ 10309

To appear in:

Journal of Molecular Liquids

Received date: Revised date: Accepted date:

16 December 2018 9 January 2019 13 January 2019

Please cite this article as: Kenan Sun, Yue Liu, Yaxu Wu, Xugeng Guo, Junfeng Li, Li Wang , Application of quantitative prediction to design new organic dyes in dye sensitized solar cells. Molliq (2019), https://doi.org/10.1016/j.molliq.2019.01.078

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ACCEPTED MANUSCRIPT Application of quantitative prediction to design new organic dyes in Dye Sensitized Solar Cells Kenan Sun, Yue Liu, Yaxu Wu, Xugeng Guo*, Junfeng Li*, Li Wang* Henan Provincial Engineering Research Center of Green Anticorrosion

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Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University,

SC

RI

Kaifeng, Henan 475004, P.R. China

Abstract

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Two new groups, cyclopentadipyrrole and dihydropyrroloindole, that has been

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applied for other relevant regions, are firstly employed as π group to compose the organic

dyes,

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(E)-3-(6-(10-butyl-10H-phenothiazin-2-yl)-4,4-dimethyl-4,7-dihydro-1H-cyclopenta

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[2,1-b:3,4-b’]dipyrrol-2-yl)-2-cyanoacrylic

acid

(PCP3)

and

(E)-3-(7-(10-butyl-10H-phenothiazin-2-yl)-1,8-dihydropyrrolo[3,2-g]indol-2-yl)-2-cy

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anoacrylic acid (PBP4), in DSSCs along with phenothiazine as donor and

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cyanoacrylic acid as acceptor. Their performance should be screened out before it would be fabricated in device. When the frontier molecular orbitals (FMO) and

*Corresponding author: 1) Xugeng Guo, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China.Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 2) Junfeng Li, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China.Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 3) Li Wang, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China. Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 1

ACCEPTED MANUSCRIPT absorption spectrum properties are studied, the performance of PCP3 and PBP4 is not better

than

that

of

(E)-3-(6-(10-butyl-10H-phenothiazin-2-yl)-4,4-dimethyl-4H-cyclopenta[2,1-b:3,4-b’] dithiophen-2-yl)-2-cyanoacrylic

acid

(PCT1)

and

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(E)-3-(7-(10-butyl-10H-phenothiazin-2-yl)benzo[2,1-b:3,4-b’]dithiophen-2-yl)-2-cyan

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oacrylic acid (PBT2). Even when the dye-TiO2 adsorbed system is considered, the

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differences among four organic dyes are too small to distinguish them, which is also perplex for most of theoretical studies. To have a reliable and accurate results, the

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values of short-circuit current density (JSC), open-circuit voltage (VOC), and

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photon-to-electron conversion efficiency (PCE) for DSSCs on the basis of four organic dyes are accurately determined. Although the JSC of PCP3 is the smaller than

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that of PCT1, the PCE of PCP3 is comparable with that of PCT1 due to the larger

every designed dyes.

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VOC. The quantitative calculation is an effective method to make a distinction among

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Keywords: FRET, photon-to-electron conversion efficiency, aggregation, dye

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sensitized solar cell, short-circuit current density 1. Introduction

Energy crisis and environmental problems have sparked the interesting to develop the new sustainable photovoltaic technologies [1]. Perovskites solar cells (PSCs) and dye sensitized solar cells (DSSCs) are two promising alternatives for classical silicon-based solar cells [2-5]. As compared with PSCs, the DSSCs are easier to be fabricated with the better stability, which is important for the commercial

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ACCEPTED MANUSCRIPT applications [6]. More importantly, the DSSCs would have outstanding performance even under ambient light conditions [7,8]. The lower photon-to-electron conversion efficiency (PCE) is the major obstacle for the application of DSSCs. As the critical component, sensitizer controls the light harvesting and injects the electrons into the

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photoanode, which plays an important role in the performance of solar cell.

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Recently, metal-free sensitizers have attracted more and more attentions due to the

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high molar extinction coefficients, flexible molecular engineering, simple synthesis and purification as well as less pollution problem [9]. D-π-A (donor-π-acceptor)

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structural motif is one of the most classical configurations for organic sensitizers,

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which is favorable for the intramolecular electron transfer. The photophysical properties of dyes are also easily tuned by variation of any moiety [10-15]. However,

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organic dyes are easy to form the aggregation on the semiconductor surface, which is

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one of the main items to lower the conversion efficiency. Inclusion of the long alkyl chain or employment of the nonplanar moiety would effectively block the formation of

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aggregation.

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Phenothiazine presents the high electron-donating ability, which is a promising candidate for the donor moiety. Moreover, its butterfly conformation would effectively block the formation of aggregations. However, the aggregation effect of organic dyes with phenothiazine donor is rarely considered in previous theoretical and experimental studies.

In

this

work,

three

new

organic

dyes,

(E)-3-(7-(10-butyl-10H-phenothiazin-2-yl)benzo[2,1-b:3,4-b’]dithiophen-2-yl)-2-cyan oacrylic

acid

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(PBT2),

ACCEPTED MANUSCRIPT (E)-3-(6-(10-butyl-10H-phenothiazin-2-yl)-4,4-dimethyl-4,7-dihydro-1H-cyclopenta[ 2,1-b:3,4-b’]dipyrrol-2-yl)-2-cyanoacrylic

acid

(PCP3),

and

(E)-3-(7-(10-butyl-10H-phenothiazin-2-yl)-1,8-dihydropyrrolo[3,2-g]indol-2-yl)-2-cy anoacrylic acid (PBP4), are firstly designed along with phenothiazine as donor and acid

as

acceptor,

which

are

built

on

the

basis

of

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cyanoacrylic

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(E)-3-(6-(10-butyl-10H-phenothiazin-2-yl)-4,4-dimethyl-4H-cyclopenta[2,1-b:3,4-b’]

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dithiophen-2-yl)-2-cyanoacrylic acid (PCT1) reported by Marszalek et al. [16]. (See Scheme 1). Although some π groups have never been employed to compose organic

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dyes, they are applied to compose organic field-effect transistors and others [17-19].

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Here, they are taken as the π group to explore the performance to be organic dyes in DSSCs.

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Until now, theoretical molecular engineering has not been a popular tool to

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design the organic sensitizers. The lack of reliable and quantitative tool to predict the performance of dyes is the predominant factor to limit its further application. Most of

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theoretical studies only focus on the qualitative determinations. To quantitatively

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predict the short-circuit current density (JSC) and open-circuit voltage (VOC) as well as PCE is still not an easy task for the theoretical calculation. Additionally, the influence of aggregation is almost neglected by both experimental and theoretical investigations in previous literature [20-23]. Aforementioned items are all considered in this work with the ultimate goal to uncover the structure-property relationship. 2. Computational details The ground-state geometry of isolated dye was optimized by unrestricted hybrid

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ACCEPTED MANUSCRIPT Perdew-Burke-Ernzerhof exchange correlation function (PBE0) with the 6-31G(d,p) basis set on all atoms [24]. The nature of optimized structures was confirmed by the frequency calculations at the same level. Based on the optimized ground-state geometries, the absorption spectra were simulated by time-dependent density

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functional theory (TD-DFT) with PBE0 method along with polarized continuum

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model (PCM) in dichloromethane (DCM) [25,26]. Aforementioned electronic

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calculations were performed by the Gaussian 09 program [27].

With regard to the dye-TiO2 adsorption system the calculations were completed

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in Vienna ab-initio simulation package (VASP) program [28-30]. The isolated dye,

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bare TiO2 surface, and dye-TiO2 system were optimized by means of projector-augmented wave methods with the generalized gradient approximation

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(GGA) using Perdewe-Burkee-Ernzerhof (PBE) exchange-correlation functional

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implemented [31]. Grimme D2 dispersion correction was included to take into account dispersion effects. The energy cutoff was set to be 400 eV and the

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optimization would stop when the force on each atom was smaller than 0.1 eV Å-1. To

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get better insight into the interfacial properties of the dye-TiO2 system, the 7 × 6 × 4 TiO2 anatase (101) supercell was taken as the adsorption surface. The periodic slabs were separated by a vacuum layer of 20 Å. Furthermore, the density of states (DOS) and projected density of states (PDOS) were calculated at the same level to deeply analyze the adsorption properties. The process of intra-type Fӧrster resonance energy transfer (FRET) between donor and acceptor was discussed, which is defined by the following equation:

5

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KF 

1  R06   0  rA  rD

  6  

(1)

Here, rA and rD are the position vectors of the energy donor and acceptor, respectively, τ0 is the lifetime of excited state for the energy donor, and the R06 is the Fӧrster radius when the FRET has 50% probability, which follows the relationship:

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9000  ln 10   2QD J ( ) 128 5 n4 N A

(2)

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R06 

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In above equation, QD is luminescence efficiency of the energy donor, J(λ) is the overlap integral of the donor emission spectrum and the acceptor absorption spectrum,

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κ2 is the orientation factor, NA is Avogadro's constant, and n is the refractive index of

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the medium. The definitions for J(λ) and κ2 please refer refs [32,33]. 3. Results and discussion

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3.1 The frontier molecular orbitals (FMOs) and absorption spectrum

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In DSSCs, the dye harvests the light and injects the excited electron into the conduction band (CB) of nanocrystalline oxide (normally TiO2). The charge hole is

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regenerated by a catalyst at the counter-electrode to form a closing circuit. According

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to the working principle, the lowest unoccupied molecular orbital (LUMO, L) energy level of dye should be higher than the CB of TiO2 (-4.0 eV) to ensure the enough injection force. At the same time, the highest occupied molecular orbital (HOMO, H) energy level of dye should be lower than the iodine/iodide redox potential (-4.8 eV) to obtain the electron to regenerate. The corresponding values are plotted in Fig. 1. All investigated dyes are eligible for the basic requirement. As compared with PCT1, the HOMO energy levels of all other three dyes are more unstabilized. The LUMO energy

6

ACCEPTED MANUSCRIPT levels of PCP3 and PBP4 shift toward the less negative values, while that of PBT2 moves toward the inverse direction. The H-L energy gap of PCP3 is the largest indicating the narrowest absorption region. However, it is not good enough to compare their performance only on the basis of isolated dyes since the energy level

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would be varied after the dye is adsorbed on the TiO2 surface.

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The simulated absorption spectra of four dyes are plotted in Fig. 2. The

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maximum absorption wavelength (λmax) of PCT1 is the largest. Moreover, the calculated λmax is in good agreement with the experimental result of 532 nm with the

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deviation of 0.04 eV [16]. The λmax of PCP3 is only 470 nm, which is consistent with

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its largest H-L energy gap. The narrow absorption region is not favorable for the light harvesting resulting in the inferior overall performance. However, the absorption

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intensity of PCP3 is the strongest, which is helpful for the refinement of efficiency. It

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is not easy to judge the performance of PCT1 and PCP3 only based on the absorption spectrum.

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3.2 Fӧrster resonance energy transfer (FRET)

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The D-π-A structure is sparked because it is favorable for the energy transfer from donor to acceptor. On the basis of definition, the FRET is determined by the following items: (1) the distance between donor and acceptor (r); (2) the spectrum overlap between the donor emission and acceptor absorption (J(λ)); and (3) the orientation of the transition dipole moment of the donor and acceptor (к2). The corresponding values are tabulated in Table 1. As compared with PCT1, PCP3 has the larger J(λ) as well as the smaller |rA-rD| suggesting the faster FRET. PBP2 has the

7

ACCEPTED MANUSCRIPT largest κ2 and PBP4 has the shortest |rA-rD|, which is also beneficial for improving the FRET. However, it is difficult to determine the relative sequence for them since no one has all prominent items. It is also the predominant block for the application of qualitative judgment. The accurate value is an assurance to have the reliable result.

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3.3 Dye-TiO2 adsorbed system

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The adsorption structures for all dyes on TiO2 (101) surface optimized by the

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first principle are plotted in Fig. 3 along with the Ti-O distance and adsorption energy. One proton is transferred to nearby surface oxygen, then, two oxygen atoms in

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carboxylate group are adsorbed on TiO2 (101) surface, which is the popular bridging

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adsorption model [34]. The adsorption energy is -0.42 eV for PCT1, -0.31 eV for PBT2, -1.03 eV for PCP3, and -0.66 eV for PBP4, respectively, which is defined by

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Eads  EdyeTiO2  Edye  ETiO2（3）. Here, the Edye , ETiO 2 , and EdyeTiO 2 refer to the total

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energies of the isolated dye, TiO2, and dye-TiO2 complex, respectively. The negative adsorbed energy means that the adsorption is spontaneous and strong, especially for

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PCP3. The dyes are favorable to adsorbing on the TiO2 surface, which is beneficial to

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increasing the dye loading and harvesting more light. However, the coupling interactions among dyes are also improved, which is inverse to the refinement of DSSCs overall efficiency. To elucidate the shift of energy level after adsorption, the DOS and PDOS for the pure and adsorbed dyes are shown in Fig. 4 along with those of TiO2 surface. As compared with the clean surface, the CB of TiO2 shifts towards the more negative values. In contrast, the LUMO of adsorbed dye moves to the more positive values. As

8

ACCEPTED MANUSCRIPT a result, the energy difference between LUMO of dye and CB of TiO 2 (ΔE (eV)) is enlarged, which would provide more injecting force for the excited electrons (See Table 2). The introduction of TiO2 greatly refines the performance of device. There are two interesting things: (1) The ΔE (eV) of PBP4 is the largest before adsorption,

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while that of PCT1 becomes the largest after adsoption. (2) After adsorption, the ΔE

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(eV) of PCP3 is greatly increased, which is not the smallest one. It is necessary to

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consider the dye-TiO2 adsorption system rather than only isolated dyes. Although the injecting force of PCT1 is slightly larger than other three dyes, the deviation among

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them is still not large enough to distinct them. The larger injecting force does not

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indicate the shorter injecting time. The injecting time of PCP3 is the smallest leading to faster electron injection.

J SCVOC FF (4), the PCE is mainly related with both JSC and Pin

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According to PCE 

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3.4 JSC, VOC, and PCE

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VOC. The fill factor (FF) and input power of incident solar light (Pin) are regarded as the constant, which is the same for all studied dyes. JSC is defined by the following

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relationship [35]:

JSC  e LHE ( )injregcollph.AM1.5G ( )

(5)

in which LHE is the light-harvesting efficiency, Φinj is the electron-injection efficiency, ηreg is the dye regeneration efficiency, ηcoll is the collection efficiency, and φph.Am1.5G is the photon flux under AM1.5G solar irradiation spectra. The Фinj, ηreg, and ηcoll are normally taken as the unit. As a result, the JSC is only determined by LHE(λ). The LHE(λ) is related with molar absorption coefficient (ε(λ)) and dye 9

ACCEPTED MANUSCRIPT concentration (Γ) via the relationship of LHE = 1 - 10 - ε( λ ) Γ (6). The ε(λ) is the molar absorption coefficient at certain wavelength, and Γ is the surface loading of sensitizers (mol·cm-2), which is assigned as experimental value of 4.72 × 10-8 mol·cm-2 [36]. The max LHE(λ) curves and their corresponding J SC are shown in Fig. 5. The simulated

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max is 17.90 mA·cm-2 for PCT1, which is in good agreement with the experimental J SC

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max value of 12.90 mA·cm-2. The J SC of other three dyes are smaller than that of PCT1,

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which is attributed to their narrow absorption region and weaker absorption intensity in the long wavelength (> 510 nm) region (See Fig. 2). Although the PCP3 has the

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strongest absorption intensity, its absorption region is much narrower than that of

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max PCT1 resulting in the smaller J SC . As to PBT2, its λmax could be comparable with

that of PCT1. However, its absorption strength is much smaller leading to the less

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max J SC is the smallest.

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max . Not only the λmax but also the absorption strength of PBP4 is the smallest, so its J SC

max Although the J SC of new designed dyes are smaller than that of PCT1, their

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PCE would not definitely be small since VOC is the other critical item to determine the

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PCE. Moreover, there is trade-off relationship between VOC and JSC. The VOC is defined by the following relationship: VOC 

ECBM  Eredox  CB kBT n  ln( c ) q q NCB

(7)

where ECBM is conduction band maximum of TiO2, ΔCB is the shift of ECBM when the dyes are adsorbed on TiO2, nc is the number of injected electrons into TiO2 due to dye adsorption, and NCB is the accessible density of conduction band states in the semiconductor. The temperature of 300 K and typical NCB density of 7 × 1020 cm−3 are 10

ACCEPTED MANUSCRIPT adopted according to the experiment [37]. The standard iodide/triiodide redox potential, -5.04 eV, is regarded as the reduction-oxidation potential of electrolyte (Eredox) [37]. The ECBM is calculated on the basis of dye-TiO2 system involving the energy shift due to the dye adsorption. Both the dye loading density and the thick of

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semiconductor are got from the literature [16]. The VOC is predominantly related with

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ECBM and nc. The calculated VOC are 1057 mV, 1357 mV, 1431 mV, and 1391 mV for

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PCT1, PBT2, PCP3, and PBP4, respectively (See Table 3). As expected, the VOC of three new designed dyes are all higher than that of PCT1. Taken the value of 0.7 for

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FF [16], PCP3 has the comparable PCE with PCT1 combined with the medium JSC

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and the highest VOC (See Table 3). For PBT2 and PBP4, their PCEs are still less than max that of PCT1 due to their much smaller J SC , although they have the larger VOC.

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There are some approximations, however, the calculated JSC and VOC are still provide

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a chance to compare the performance of a series of dyes that are difficult to be completed by qualitative comparison. The deviation between calculated VOC and

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refined.

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corresponding experimental result is much larger, which is deserved to be further

3.5 Aggregation influence To easily form the aggregation is the fatal shortcoming for the D-π-A dye, which is called as the “dark” current. The aggregation would be formed not only in the solution but also on the TiO2 surface for organic dyes. Two dyes are adsorbed on the TiO2 (101) surface as the most simple aggregation model. As shown in Fig. 6, there is obviously π-π interaction between two dyes resulting in the strong electronic coupling

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ACCEPTED MANUSCRIPT between them, which would weaken the electron injection into the TiO2. The electronic coupling between stacking monomers is studied by the direct method, which is defined via the relationship: 0, site1 0 0, site 2 0, site1 0, site 2 V12  LUMO / HOMO F LUMO / HOMO  LUMO / HOMO hcore LUMO / HOMO 



0, site 2 0, site1 0, site 2 0 0  LUMO / HOMO  LUMO / HOMOLUMO / HOMOl l

0, site1 0 LUMO / HOMO l

(8)

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l ( occ )



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0, site1 where V12 is the charge transfer integral for the electron/hole and LUMO / HOMO and

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0, site 2 LUMO / HOMO represent the LUMO/HOMO of two adjacent molecules 1 and 2 when no

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intermolecular interaction is presented. F0 is the Fock operator and its density matrix is constructed from orbitals of two adjacent molecules [38,39]. The V12 of PBT2 (0.19

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eV), PCP3 (0.53 eV), and PBP4 (0.14 eV) are all smaller than that of PCT1 (0.82 eV) indicating the larger electronic coupling for the latter. The device based on PCP3 has

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not only the comparable PCE but also the smaller aggregation effect leading to the better performance than the device based on PCT1. Certainly, the effect of

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aggregation is not limited to the negative, which would also increase the dye loading amount leading to the more light harvesting. However, it is included in the calculation

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of PCE, which is not stated out alone. 4. Conclusion

The properties of four organic dyes with D-π-A configuration are theoretically investigated by the DFT and first principle. Among them, three new organic dyes, PBT2, PCP3, PBP4, are designed on the basis of PCT1 reported in literature. The energy gaps between HOMO and LUMO for PCP3 and PBP4 are larger than that of PCT1 leading to the smaller absorption region indicating the less performance of 12

ACCEPTED MANUSCRIPT DSSC. The situation is not refined when the FRET is considered. Although PCP3 has the largest J(λ) and the smaller |rA-rD|, its к2 is the smallest. The FRET of PCP3 could not be the largest. No one presents the obvious advantages to distinct them. Besides the isolated system, the dye-TiO2 adsorbed system is considered. After adsorption, the

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energy difference between LUMO of dye and CB of TiO2 is enlarged to ensure the

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max enough injecting force for electrons. The calculated J SC of PCP3 is the smaller

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than that of PCT1, which is consistent with its narrow absorption region. However, the VOC of PCP3 is the larger than that of PCT1 resulting in the comparable PCE. The

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PBP4 has the worst performance with the least PCE. More importantly, PCP3 has the

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smaller electronic coupling than PCT1 for the dimer, which is also favorable for the improvement of PCE. Taken cyclopentadipyrrole as π group is helpful to enhance the

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overall performance.

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Acknowledgements

We thank the National Supercomputing Center in Shenzhen (Shenzhen Cloud

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Computing Center) for providing computational resources and softwares. This work was supported by the National Natural Science Foundation of China (21503069,

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21676071, 21703053), Program for He’nan Innovative Research Team in University (15IRTSTHN005),

Scientific

Research

Foundation

of

Henan

University

(2015YBZR009). References

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ACCEPTED MANUSCRIPT [20] Y.Z. Li, Y.C. Li, P. Song, F.C. Ma, Y.H. Yang, Electric field effect on multi-anchoring molecular architectures: electron transfer process and opto-electronic property, J. Mol. Liq. 261 (2018) 123-136. [21] Y. Wen, W. Wu, Y. Li, W. Zhang, Z. Zeng, L. Wang, Z. Zhang, First principles study of thieno[2,3-b]indole-based organic dyes for dye-sensitized solar cells:

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screen novel π-linkers and explore the interface between photosensitizers and

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TiO2, J. Power. Sources. 326 (2016) 193-202.

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[22] K. Sun, Y. Ma, W. Zhang, Y. Wen, L. Wang, Z. Zhang, New carbazole-based dyes with asymmetric butterfly structure for dye-sensitized solar cells: design and

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properties studies, Dyes Pigments. 139 (2017) 148-156.

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[23] W. Zhang, J. Wu , Y. Wen, W. Wu, L. Wang, First principles study on interface between dual-channel anchorable organic dyes and TiO2 for dye-sensitized

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[25] M. Cossi, V. Barone, B. Mennucci, J. Tomasi, Ab initio study of ionic solutions by a polarizable continuum dielectric model, Chem. Phys. Lett. 286 (1998)

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ACCEPTED MANUSCRIPT Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery, Jr., J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,

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J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene,

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J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.

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Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G. A. Voth, P. Salvador, J.J.

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Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J.

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Cioslowski, D.J. Fox, Gaussian 09, revision A.02; Gaussian, Inc.: Wallingford, CT, 2009.

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[28] G. Kresse, J. Furthmüller, Efficient iterative schemes for ab initio total-energy

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calculations using a plane-wave basis set, Phys. Rev. B. 54 (1996) 11169. [29] G. Kresse, J. Furthmüller, Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set, Comp. Mater. Sci. 6

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ACCEPTED MANUSCRIPT [33] J. Mårtensson, Calculation of the Förster orientation factor for donor-acceptor systems with one chromophore of threefold or higher symmetry: zinc porphyrin, Chem Phys Lett. 229 (1994) 449-456. [34] M. Pastore, F. De Angelis, Computational modelling of TiO2 surfaces sensitized by organic dyes with different anchoring groups: adsorption modes, electronic

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structure and implication for electron injection/recombination, Phys. Chem.

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imidazolidin derivative: Quantum chemical investigations, J. Saudi. Chem. Soc. 20 (2016) 680-685. [39] A. Irfan, A. Kalam, A.R. Chaudhry, A.G. Al-Sehemi, S. Muhammad, Electro-optical, nonlinear and charge transfer properties of naphthalene based compounds: a dual approach study, Optik. 132 (2017) 101-110.

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Table 1. Calculated FRET parameters for PCT1, PBT2, PCP3, and PBP4. Dye

J(λ) /M cm-1nm4

|rA-rD| /Å

PCT1

1.92×1015

5.35

PBT2

1.36×1015

4.77

PCP3

2.09×1015

4.73

0.13

PBP4

1.15×1015

4.00

0.13

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Table 2. The calculated adsorption energy (Eads), the energy difference between the CB of TiO2 and the LUMO of dye (ΔE), and electron injection time (τinj) for the

ΔE (eV)a

ΔE (eV)b

τinj (fs)

PCT1

-0.42

0.13

1.26

0.76

PBT2

-0.31

0.19

0.93

0.77

PCP3

-1.03

0.04

0.99

0.69

PBP4

-0.66

0.26

0.96

0.72

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Eads (eV)

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dye-TiO2 adsorbed system.

a

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max Table 3 Estimations of nc, VOC, J SC , and PCE for all dyes and corresponding experiment electrochemical parameters for PCT1 [16].

dye

nc (cm-3)

ECBM(eV)

VOC (mV)

max (mA·cm-2) J SC

PCE (%)

VOC (exp; mV)

PCT1

7.3×1019

-3.92

1057

17.90

13.24

774

PBT2

6.8×1019

-3.62

1357

13.31

12.64

PCP3

8.5×1019

-3.55

1431

13.38

13.40

PBP4

7.0×1019

-3.59

1391

11.10

10.81

D E

T P E

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JSC (exp; mA·cm-2) 12.9

PCE (exp; %) 7.0

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Scheme 1. The sketch structures of all the investigated dyes.

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Fig. 1. Energy diagram of HOMO and LUMO for all dyes calculated at the

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PBE0/6-31G(d,p) level of theory, CB of TiO2, and redox potential of iodine/iodide.

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Fig. 2. The UV/Vis absorption spectra of all dyes calculated in dichloromethane at the

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PBE0/6-31G(d,p) level of theory along with the experimental value for PCT1 [16].

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Fig. 3. The graph a) is the adsorption configuration of dye-TiO2. The graph b) is the detail of adsorption including the adsorption energy (eV)

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Fig. 4. Calculated DOS and PDOS for clean TiO2 surface and interfaces of TiO2 adsorbed with PCT1 (a), PBT2 (b), PCP3 (c), and PBP4 (d).

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max Fig. 5. Simulated J SC (in mA cm-2) and light-harvesting efficiency LHE(λ) of all

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T P

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D E

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C C

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Fig. 6. The graph a) is the top view and side view of TiO2 surface adsorbed with dimer dyes, The graph b) is the detail of adsorption including the

adsorption energy (eV) and dimer configuration.

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ACCEPTED MANUSCRIPT Graphical Abstract Application of quantitative prediction to design new organic dyes in Dye Sensitized Solar Cells Kenan Sun, Yue Liu, Yaxu Wu, Xugeng Guo*, Junfeng Li*, Li Wang*

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Henan Provincial Engineering Research Center of Green

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Anticorrosion Technology for Magnesium Alloys,

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College of Chemistry and Chemical Engineering, Henan University, Kaifeng,

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Henan 475004, P.R. China

*

Corresponding author 1) Xugeng Guo, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China. Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 2) Junfeng Li, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China. Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 3) Li Wang, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China. Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 29

ACCEPTED MANUSCRIPT Highlights Application of quantitative prediction to design new organic dyes in Dye Sensitized Solar Cells Kenan Sun, Yue Liu, Yaxu Wu, Xugeng Guo*, Junfeng Li*, Li Wang*

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Henan Provincial Engineering Research Center of Green

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Anticorrosion Technology for Magnesium Alloys,

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College of Chemistry and Chemical Engineering, Henan University,

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Kaifeng, Henan 475004, P.R. China

The accurate values of JSC, VOC, and PCE are calculated.

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Aggregation effect on the overall performance is considered.

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π groups applied in relevant regions would also be employed to design organic

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dyes.

*Corresponding author: 1) Xugeng Guo, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China.Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 2) Junfeng Li, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China.Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 3) Li Wang, Henan Provincial Engineering Research Center of Green Anticorrosion Technology for Magnesium Alloys, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China. Tel: +86-371-22196667; Fax: +86-371-22196667. E-mail: [email protected] 30