Design of front emitter layer for improving efficiency in silicon heterojunction solar cells via numerical calculations

An a-Si:H (p) window layer is used in silicon heterojunction (SHJ) solar cells; however, it is limited by short-circuit current density (J(SC)). In general, an emitter with a high doping concentration is appropriate for contact with a transparent conducting oxide (TCO); however, it is influenced by side effects such as a reduction of J(SC) through optical absorption. The conductivity of the emitter is lowered as its doping concentration is reduced, resulting in a decrease in V-OC and FF. We investigated p-type emitters such as those made of a-Si:H, a-SiC:H, and mu c-SiO:H through film analysis and AFORS-HET simulation to improve the conversion efficiency of the device. Prior to conducting a simulation, a fabricated SHJ solar cell was used to theoretically calculate the precise parameter values. The obtained efficiency was 22.03 % when V-OC=730 mV, J(SC)=39.63 mA/cm(2), and FF = 76.13 %. Based on the fitted structure, we conducted experiments to test the emitter materials within a wide band gap and performed a simulation. In the case of mu c-SiO:H (p), the achieved efficiency was 24.23 % when V-OC=736.6 mV, J(SC)=40.15 mA/cm(2), and FF = 81.93 %.