Simulation of the Functionality of ZnO, TiO2, Ta2O5, and MoO2 Carrier Selective Contacts of GaAs0.99Bi0.01 Nanowire based Solar Cells

Abstract Photovoltaic performance of perpendicularly aligned GaAs0.99Bi0.01/CSC/ITO core-shell nanowire solar cell is thoroughly investigated in this simulation based theoretical study for both electron selective contact (ESC) and hole selective contact (HSC) as carrier selective contact (CSC) shell around GaAs0.99Bi0.01 core nanowire. The overall performance has been compared with radial PiN doped GaAs0.99Bi0.01 NWSC to mark the improvement caused by carrier selectivity. ZnO, TiO2, and Ta2O5 materials have been chosen as ESC material and MoO2 is chosen as HSC material in order to carry out this comparative study. We have thoroughly performed geometry optimization test over a wide range of periods in order to select the optimized ITO (Indium Tin Oxide) thickness for obtaining maximum photo current generation. The maximum short circuit photo current density (Jsc) of 38.76 mA/cm2 is obtained with ZnO coated nanowire solar cell (NWSC) for a pitch (P) of 400 nm and ITO shell thickness of 90 nm. For this optimized geometry, TiO2, Ta2O5 and MoO2 coated structures offered Jsc of 35.82 mA/cm2, 35.69 mA/cm2, and 35.27 mA/cm2 respectively and the uncoated NW generated Jsc of 31.15 mA/cm2. The planar structure without coating exhibits a Jsc of 24.86 mA/cm2, which is significantly lower than the nanostructured solar cells. Finally Lumerical 3D charge transport simulator is used to perform the electrical stimulation of ZnO coated structure, which offers maximum ideal Jsc. A detailed electrical performance analysis of GaAs0.99Bi0.01/CSC/ITO unit nanowire solar cell for ZnO, TiO2, Ta2O5 as ESC and MoO2 as HSC have also been covered in this article which reveals that ZnO as ESC possesses promising potential for designing highly efficient solar cells as it offers a photo conversion efficiency(PCE) of the order of 25% and open circuit voltage (Voc) even for very less minority carrier lifetime (Ʈn) 0.1 ns of GaAs0.99Bi0.01 and 1ps Ʈn of ZnO.