MoOx Hole Collection Layer for a-Si:H Based Photovoltaic Cells

Abstract

ABSTRACTAn experimental investigation to verify the suitability of MoOx as the hole collection layer for a-Si:H based thin film photovoltaic cell is carried out. The photovoltaic cell investigated has the structure of MoOx (hole collection layer) / intrinsic a-Si:H (photoactive layer) / phosphorus doped a-Si:H (electron collection layer) / Ag (back reflector electrode); all deposited in that order onto an Asahi glass (type U) substrate, which is also acting as the transparent front electrode for the cell. The effects of different post deposition annealing temperatures are investigated. The highest efficiency values are obtained for the cells annealed at 120°C. For the photovoltaic cell with 100 nm thick photoactive layer, the highest efficiency is measured to be 6.46 % with an open current voltage (Voc) of 827 mV and a short current density of (Jsc) of 10.44 mA/cm2. For the photovoltaic cell with 300 nm thick photoactive layer, the highest efficiency is measured to be 7.93 % with Voc of 818 mV and Jsc of 13.24 mA/cm2. The efficiency measurements are carried out under AM1.5 test conditions. Jsc values are corrected according to the external quantum efficiency measurements of the cells in the AM1.5 photovoltaic spectrum region between 270 nm and 800 nm. Compared to the reference cell with boron doped μ-SiOx layer acting as the hole collection layer, the cell with MoOx hole collection layer has similar FF, lower Voc, higher Jsc for wavelength up to the green light region of the AM1.5 spectrum and lower Jsc for the longer wavelengths.