Current Enhancement of Ultrathin GaAs Solar Cells with Rear Light Scattering Structures Using Block Copolymers

Ultrathin GaAs solar cells have gained attention because they are cost-effective and exhibit high carrier-collection efficiency and open-circuit voltage compared with cells with thicker absorber layers. However, ultrathin GaAs solar cells have a low current density due to their thin light-absorbing layers. To improve the photoabsorption of ultrathin GaAs solar cells, light-trapping structures with textured front or rear surfaces are necessary, and easy methods for fabricating textured structures are required. In this study, a new method to create light-scattering textured surfaces using block copolymers is developed. This method only requires spin coating, annealing, and wet etching, making it easily applicable to large-area devices such as solar cells. An ultrathin GaAs solar cell is fabricated with a rear-textured structure using block copolymers as masks for wet etching. The results demonstrate that the short-circuit current density is enhanced by 1.39 mA cm-2, which improves the energy conversion efficiency by 0.71 percentage points compared with a reference cell without a rear-textured structure. Herein, a simple method to fabricate a light-scattering textured structure using block copolymers is proposed and demonstrated. By inserting this structure into the rear side of ultrathin GaAs solar cells, the photoabsorption is enhanced owing to light trapping. With this method, the realization of highly efficient and low-cost solar cells is expected.image (c) 2023 WILEY-VCH GmbH