Performance augmentation of radiation-resilient III-nitride based multi-junction solar cells with varying composition and thickness of the cap layer

This paper presents performance optimization of III-nitride based multi-junction solar cells using AlGaN cap layer engineering. The Al mole fraction from 0.04 to 0.1 in AlGaN cap layer and its thickness ranging 0.2 – 0.5 µm of solar cell structures are varied and numerical simulation results are obtained using well-calibrated Sentaurus TCAD. The best performance of such solar cells is obtained for Al0.06Ga0.94N cap material having the thickness of 0.4 µm. Our optimized solar cell yields short-circuit current density of 8.19 mA.cm-2, open circuit voltage of 0.95V, fill-factor of 88% and power conversion efficiency of 6.84 %. Notably, at AM1.5 sun irradiance, the optimized solar cell exhibits about 79% increase in power conversion efficiency over the standard structure.