Effect of Low-Angle Grain-Boundary Passivation in Flexible Single-Crystal-Like Thin-Film GaAs Solar Cells

We theoretically and experimentally study the effect of defect-state passivation at low-angle grain boundaries (LA-GBs) on the photovoltaic performance characteristics of flexible single-crystal-like thin-film GaAs SCs. The 2D modeling of the SCs shows that LA-GBs in the single-crystal-like GaAs still limit their performance, especially for open-circuit voltage (V
OC
), and effective passivation of the LA-GBs can boost the photo-conversion efficiency remarkably. Two physical hydrogen-based passivation techniques and a chemical sulfide treatment are employed for the passivation of the LA-GBs in the single-crystal-like GaAs. Current-voltage (I-V) and photoluminescence (PL) characterization studies demonstrate that sulfur by trioctylphosphine sulfide (TOP: S) solution passivation treatment can significantly increase PL peak intensity and the performance characteristics of flexible single-crystal-like GaAs SCs. A substantial improvement is achieved with increases of ~20%, ~10%, ~13%, and ~65% for V
OC
, short-circuit current (J
SC
), fill factor (FF), and overall efficiency, respectively.