Design of InGaP//GaAs Thin-film Tandem Solar Cell Architecture for Challenging Environments

Abstract

The power conversion efficiency of the single junction solar cell is approaching the theoretical limits, which leads to the development of tandem cells. Among various solar cell materials, compound semiconductors such as GaAs and InGaP are the large band gap materials preferred for multijunction solar cells. Besides the broad-spectrum absorption, GaAs and InGaP possess hightemperature stability, radiation resistance, longer minority carrier lifetime, and higher electron mobilities compared to the widely used Si for photovoltaics. The work reports the simulated InGaP//GaAs thin film tandem cell architectures to enhance the overall cell efficiency. The optimization of the doping concentration and the active layer thickness of the InGaP top cell lead to 30.7% efficiency under standard illumination. The optimized thickness of the n-type emitter and p-type absorber layer of the InGaP top cell are 100 nm and 6 μm, respectively. The filtered spectrum is generated from the InGaP top cell for optical coupling. The optimized GaAs bottom cell is 9.1% efficient under filtered spectrum for emitter thickness of 50 nm and absorber thickness of 10 μm. The two-terminal (2T) and four-terminal (4T) tandem configuration are 37.2% and 39.8%, respectively. The bonding of the tandem architecture considers a transparent ideal insulator and conductor for 4T and 2T architecture, respectively. The optimized cell configuration is also tested for high-temperature (up to 450 K) and low-illumination (0.1 Sun) conditions. As the proposed cell is a thin-film tandem cell with minimal material utilization, it sets a new avenue in photovoltaics for space applications.