Double p-SiOx layers to improve the efficiency of p–i–n a-SiGe:H thin film solar cells

Abstract

In this work, p–i–n hydrogenated amorphous silicon germanium (a-SiGe:H) thin film solar cells were fabricated by using double p-type silicon oxide (p-SiOx) layers, and the power conversion efficiency (PCE) was increased from 7.79 to 9.10%. The optoelectronic properties and functions of p-SiOx layer in a-SiGe:H cells were measured and discussed. A window layer (~ 20 nm) was deposited and characterized to determine the optimal single p-SiOx layer parameters. After that, an ultra-thin contact layer (~ 4 nm) of p-SiOx was deposited in front of the window layer. Through comparative analyses between single and double p-SiOx layers, the performance of the device has greatly improved in open-circuit voltage (Voc), fill factor (FF) and short-circuit current density (Jsc). The optimization of interface contact between top transparent conductive oxide (TCO) and p-layer effectively improves the device efficiency. Finally, a-SiGe:H solar cell with high Voc = 750 mV, FF = 68.36% and Jsc = 17.75 mA/cm2 were fabricated successfully. A high efficiency of 9.10% has been achieved by double p-SiOx layers for a-SiGe:H thin film solar cell.