Introduction, Characterization and Efficiency Optimization of a Heterojunction Solar Cell with GaAs as Back Surface Field (BSF) Layer Using ADEPT/F

Abstract

Energy is convertible from one form to another. So, energy conversion efficiency is a major issue for photovoltaic cells today. Researchers are continuously trying to improve the efficiency level of photovoltaic devices by introducing new materials and advanced concepts. The target is to reach a high efficiency level within affordable cost, which will lead to a mass generation of electricity using photovoltaic devices. In this work, a III-V heterojunction solar cell has been introduced and characterized, which uses an AlGaAs heterojunction as the working p-n junction. ADEPT/F, a 1D simulation software, was used throughout the whole work for the simulation of light J-V characteristics for different designs. Energy conversion efficiency for each design was calculated from its corresponding light J-V characteristics curve. An illumination level of 1000 W/m2 (AM1.5G standard) and a concentration level of 1 sun was considered for all the simulations in the work. The photovoltaic cell has an n-on-p structure,where the p-type AlGaAs layer acts as a base, and the n-type ZnS layer serves as the emitter. The base thickness was kept at 1μm. Germanium (Ge) substrate (p-doped) was used for the structure. Considering the high fabrication cost of III-V solar cells, a thin film solar cell design was proposed,which is only 2 μm thick (excluding the substrate thickness), and yields an efficiency of 12.16%.This efficiency was raised to 13.84% by using InP substrate, instead of Ge. We used ADEPT software for simulating J-V curve. From the curves, we got Open circuit voltage Voc and short circuit current Isc . Then, from these, Fill Factor and efficiency were calculated.