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Structural and chemical characterization of photovoltaic materials and devices
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Solar Cells, 1 ( 1 9 7 9 / 8 0 ) 158 © Elsevier Sequoia S.A., L a u s a n n e - - P r i n t e d in t h e N e t h e r l a n d s
S T R U C T U R A L AND CHEMICAL C H A R A C T E R I Z A T I O N OF PHOTOVOLTAIC MATERIALS AND DEVICES*
J O H N D. M E A K I N
Institute of Energy Conversion, University of Delaware, Newark, Del. 19711 (U.S.A.)
In its most general form a solar cell is composed of five distinct layers. These are the two semiconductors which make up the junction, two ohmic contacts and a transparent encapsulating and antireflecting layer. In order to understand the structure and operation of this multilayer device, generally with a view to improving its performance, it is necessary to build up an extensive data base covering both the individual components and the interfaces and interactions between the discrete layers. A complicating factor is that in many instances the behavior of the c o m p o n e n t layers cannot be predicted from the known and understood properties of the corresponding bulk material. As a direct consequence of the thickness of the layers, profound effects on phase and chemical stability can frequently be observed. The interface region between contiguous layers may also play a dominant role in the performance of a given cell and regions less than 50 A thick must often be detected and characterized before a full accounting of cell behavior is possible. Finally we are concerned with a large-area device which is inherently susceptible to defects that may be few in number and low in areal density. Unless such flaws can be either eliminated or neutralized many cell measurements will owe more to the defects than to the considerably larger defect-free cell area. To attack the problem of fully characterizing the structural and chemical build-up of a thin film solar cell there is n o w an impressive array of experimental and analytical techniques available. It remains true, however, that unless the choice of techniques is well planned and the analytical results are integrated into a very broadly based study the results of using even the most sophisticated tools will be an accumulation of data and not necessarily an increase in either real knowledge or understanding.
* A b s t r a c t o f a p a p e r p r e s e n t e d a t the Photovoltaic Material and Device Measurem e n t W o r k s h o p , " F o c u s o n P o l y c r y s t a l l i n e T h i n Film Cells", A r l i n g t o n , Virginia, U.S.A., J u n e 11 - 13, 1979.
Solar Cells, 1 ( 1 9 7 9 / 8 0 ) 158 © Elsevier Sequoia S.A., L a u s a n n e - - P r i n t e d in t h e N e t h e r l a n d s
S T R U C T U R A L AND CHEMICAL C H A R A C T E R I Z A T I O N OF PHOTOVOLTAIC MATERIALS AND DEVICES*
J O H N D. M E A K I N
Institute of Energy Conversion, University of Delaware, Newark, Del. 19711 (U.S.A.)
In its most general form a solar cell is composed of five distinct layers. These are the two semiconductors which make up the junction, two ohmic contacts and a transparent encapsulating and antireflecting layer. In order to understand the structure and operation of this multilayer device, generally with a view to improving its performance, it is necessary to build up an extensive data base covering both the individual components and the interfaces and interactions between the discrete layers. A complicating factor is that in many instances the behavior of the c o m p o n e n t layers cannot be predicted from the known and understood properties of the corresponding bulk material. As a direct consequence of the thickness of the layers, profound effects on phase and chemical stability can frequently be observed. The interface region between contiguous layers may also play a dominant role in the performance of a given cell and regions less than 50 A thick must often be detected and characterized before a full accounting of cell behavior is possible. Finally we are concerned with a large-area device which is inherently susceptible to defects that may be few in number and low in areal density. Unless such flaws can be either eliminated or neutralized many cell measurements will owe more to the defects than to the considerably larger defect-free cell area. To attack the problem of fully characterizing the structural and chemical build-up of a thin film solar cell there is n o w an impressive array of experimental and analytical techniques available. It remains true, however, that unless the choice of techniques is well planned and the analytical results are integrated into a very broadly based study the results of using even the most sophisticated tools will be an accumulation of data and not necessarily an increase in either real knowledge or understanding.
* A b s t r a c t o f a p a p e r p r e s e n t e d a t the Photovoltaic Material and Device Measurem e n t W o r k s h o p , " F o c u s o n P o l y c r y s t a l l i n e T h i n Film Cells", A r l i n g t o n , Virginia, U.S.A., J u n e 11 - 13, 1979.