Effect of gradually increasing germane flow rate during the deposition on the performance of a-SiGe:H solar cell

Abstract

In this paper, we fabricated a hydrogenated amorphous silicon-germanium ( a - SiGe : H ) thin film solar cell with gradually increasing GeH 4 flow rate in order to absorb long wavelength of solar spectrum without stacked structures such as tandem or triple junctions. The thin film solar cell with the a - SiGe : H in its intrinsic layer deposited using 13.56 MHz radical-assisted/plasma-enhanced chemical vapor deposition (RA/PECVD) was characterized according to several conditions of gradually varying GeH 4 flow rate. Under AM 1.5 G conditions, open-circuit voltage (V OC ), short-circuit current density (J SC ), fill factor and efficiency have been investigated. Also, external quantum efficiency (EQE) was measured. As a result, the best value of V OC , J SC and fill factor were 0.42 V, 24.16 mA/cm2 and 0.52, respectively. Efficiency of the solar cell was up to 5.3%, and EQE in the wavelength range of 400–800 nm occupied most of photon absorption.