Potential high efficiency of GaAs solar cell with heterojunction carrier selective contact layers

Advanced configurations of gallium arsenide (GaAs) solar cells are proposed, using hydrogenated amorphous silicon (a-Si: H) and zinc oxide (ZnO) layers as passivation and carrier selective contacts (CSC), as alternatives to the conventional epitaxial GaInP CSC layers. The cell operation is simulated based on the AFORS-HET simulation program. The results show that with a wide-gap ZnO window layer, single-junction GaAs solar cells can reach a higher short-circuit current density (J_sc) and open-circuit voltage (V_oc) than that obtained with conventional GaInP CSC layers without affecting the fill factor (FF). Notably, wide-gap and n-type doping ZnO layers show great potential as electron selective contacts in GaAs solar cells with high barriers at the valence band for blocking hole-transport. An efficiency of 30% is reached for a single-junction GaAs cell with a front ZnO electron selective contact. A 4-terminal GaAs/c-Si tandem solar cell configuration with an estimated conversion performance of 35.16% is proposed. These results indicate enormous potential for the development of low-cost and high-efficiency GaAs-based solar cells in the future.