The simulated performance of c-Si/a-Si:H heterojunction solar cells with nc-Si:H, µc-Si:H, a-SiC:H, and a-SiGe:H emitter layers

Abstract

The performance of c-Si/a-Si:H heterojunction solar cells with different emitter layers is studied by using the automat for simulation of heterostructures (AFORS-HET) tool. The a-Si:H(p) layer in the Ag/ZnO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n)/Ag heterojunction solar cell is replaced by an nc-Si:H(p), µc-Si:H(p), a-SiC:H(p), and a-SiGe:H(p) emitter layer. The performance of the c-Si/a-Si:H heterojunction solar cell is evaluated by varying the bandgap of these emitter layers. An open-circuit voltage (Voc) of 763.3 mV, short-circuit current density (Jsc) of 41.89 mA/cm2), fill factor (FF) of 85.61%, and efficiency (ɳ) of 27.39% were obtained at 1.8 eV for the a-Si:H(p) emitter layer. The solar cell performance is improved by replacing the a-Si:H(p) layer with an nc-Si:H(p) layer, resulting in estimated values of 764.8 mV, 43.27 mA/cm2, 85.54%, and 28.27% for Voc, Jsc, the FF, and ɳ, respectively, at 1.9 eV. The c-Si/a-Si:H heterojunction solar cell with the µc-Si:H(p) emitter having a bandgap of 1.5 eV shows a good improvement in performance with Voc, Jsc, FF, and ɳ values of 764.8 mV, 42.75 mA/cm2, 85.82%, and 28.06%, respectively. The wide bandgap and low absorption coefficient of the a-SiC:H emitter layer improve the open-circuit voltage (764.8 mV) as well as short-circuit density (42.69 mA/cm2) and thereby the efficiency (27.93%) compared with the a-Si:H(p) emitter layer. The estimated results for the c-Si/a-Si:H heterojunction solar cells having an a-SiGe:H emitter layer reveal poor performance at the low bandgap, which is improved as the bandgap of the a-SiGe:H layer is increased. The best performance with a Voc of 764.8 mV, Jsc of 42.96 mA/cm2, FF of 85.54%, and ɳ of 28.09% at 1.7 eV is obtained for the a-SiGe:H layer.