Trapezoidal structure for enhancing absorption in upright ultra-thin crystalline silicon solar cells

• A trapezoidal surface structure is proposed for ultrathin c-Si solar cells. • Achieves >80% average absorption from 350–1100 nm and >90% under AM1.5G. • Local field amplification from multi-path scattering boosts light trapping. • Delivers a power conversion efficiency of 20.9% in upright configuration. Surface nanostructuring provides an effective route to enhance absorption and photoelectric conversion efficiency in crystalline silicon (c-Si) solar cells. Particularly, optimized surface targeting upright solar cells can not only enhance absorption performance but also significantly expand their application scenarios. This study presents an ultra-thin c-Si solar cell with a trapezoidal nanostructure. Without relying on additional materials, the absorption performance under large-angle (30°–60°) installation conditions is improved solely through geometric optimization. Simulation results indicate that the cell exhibits an average absorption exceeding 80% across the 350-1125 nm wavelength range and an effective absorption above 90% for the AM1.5G solar spectrum. Performance comparisons with other structures confirm that the superiority of this design stems from its enlarged light-receiving area and optimized light-trapping path. Analysis of the electric field distribution indicates that the absorption enhancement stems from localized field amplification driven by multi-path light reflection and scattering. Electrical output calculations further confirm the superior performance of the proposed cell, which outperforms all compared structures, achieving a V oc of 0.635 V, an FF of 83.4%, and a PCE of 20.9%. This work makes a meaningful contribution to the development of high-efficiency ultra-thin c-Si solar cells under large-angle installation conditions.