Conformal PDMS films for strengthening flexibility and retaining absorption in pyramid ultra-thin c-Si solar cells

Abstract

Ultra-thin c-Si solar cells with the advantages of flexibility, translucence and portability are weakened in the performance of flexibility due to the surface light trapping structure, which reduces its future application potential. In this work, we designed a conformal PDMS film on the Si surface with pyramid structure to greatly inhibit the stress concentration on the surface and enhance the flexibility of ultra-thin c-Si solar cells. The maximum decrease of the Si surface stress can reach 71.19%, from 232.07 N/m2 of the pyramid structure to 66.86 N/m2 of the conformal PDMS film. In this process, it is found that at the stress concentration position, the conformal PDMS film can change the included angle of stress directions from 180° to 90° for reducing the probability of Si wafer rupture. In addition, the refractive index change in the vertical direction of the conformal PDMS film is more moderate, which can achieve the reflection reduction to improve the light absorption from 91.36% to 94.17%. Using multi physical simulation to evaluate the mechanical and photoelectric properties, the ultra-thin c-Si solar cell with conformal PDMS film has the best comprehensive performance, with the maximum surface stress of 74.59 N/m2 and the power conversion efficiency (PCE) of 19.04%, which is reduced by 49.49% and increased by 4.27%.