Characterization and optimization of amorphous silicon solar cells by variation of device geometry

Characteristics of N-I-P hydrogenated amorphous silicon solar cells have been studied systematically by varying the thickness of each layer. Open circuit voltage and fill factor increased from 807 mV to 896 mV and from 0.37 to 0.61, respectively, by increasing thickness of the N-layer from 40 A to 160 A. Short circuit current density increase from 9.2 mA/cm²to 11 mA/cm²by increasing N-layer thickness from 40 Å to 70 Å but decreased thereafter due to the dead layer effect. Increasing the undoped layer (I) thickness from 0.25 m to 1.0 m caused short circuit current to increase from 8.1 mA/cm²to 10.2 mA/cm²while fill factor decreased from 0.6 to 0.34. Dark I-V analysis, the variation of short circuit current vs open circuit voltage and spectral response data are presented. Optimum device structure, for an efficiency exceeding 7%, is 700 A ITO/120 ± 20 A N/0.5 m I/ 300-600 Å P/stainless steel substrate.