A comparison of fill factor and recombination losses in amorphous silicon solar cells on ZnO and SnO 2

Abstract

Effects of ZnO and SnO 2 TCO (Transparent Conductive Oxide) substrate materials on hydrogenated amorphous silicon (a-Si:H) p-i-n solar cell performances and recombination kinetics have been investigated. DC and Frequency-resolved photocurrent measurements in a-Si:H p-i-n solar cells of 6 have been carried out experimentally. In particular, the I– V characteristics in the dark and light, the quantum efficiency spectra, the intensity-, bias voltage- and frequency-dependence of photocurrent were obtained. Fill factor (FF) values were determined from I– V characteristics for both types of substrate cells under various illumination levels. The exponent v in the power–law relationship, I ph α G v , between generating flux density and photocurrent were determined at different bias voltages (DC) and modulation frequencies. High values of V oc (open-circuit voltage), FF, and DC exponent v for the a-Si:H p-i-n solar cell with SnO 2 were obtained, but the integrated QE (quantum efficiency), the modulated exponent v were found to be low compared to cells prepared on ZnO substrates. Our results show that these parameters are sensitive to the ZnO and SnO 2 substrate materials which act as a window layer allowing most of the incident light to pass into the i-layer of p-i-n cells.