Advanced optoelectronic simulations for ultrathin crystalline silicon solar cells with rationally designed nanopatternings

Abstract

With the rapid development of photovoltaic (PV) technology, ultrathin crystalline silicon (c-Si) solar cells (SCs) with the thickness of only 10 ‼ 20 µm have attracted tremendous attention due to the reduced material loss and a high photoelectric conversion efficiency (PCE). However, the shortened active layer decreases the optical-path of incident light substantially and thus lowers optical absorption efficiency. The surface textures are the optimal ways to improve the light-harvesting efficiencies by suppressing the reflection of the entire system and coupling incident light into the underlying absorber layer. In this report, we study the light-trapping performances of two typical surface nanostructures [i.e., inverted-nanopyramid (INP) and nanopencil (NP)] with the aid of the three-dimensional (3D) optoelectronic simulation that based on the finite-element method (FEM). We investigated theoretically the light-harvesting properties of 20 µmthick c-Si thin films structured by INPs with three typical periodicities (i.e., 300, 670, and 1400 nm) and their combined designs (i.e., front, rear and double-sided surface textures). As a result, the optimized design yields a photocurrent density (J ph ) of 39.86mA/cm2, which is about 76% higher than the flat counterpart and is only 3% lower than the value of Lambertian limit. Besides, we have verified experimentally the results, which are well-matched with the simulated one. For NP, excellent light-trapping can be achieved by adjusting the configurations of the top portion (i.e., pitch, diameter and height, et al.). The broadband enhancement in optical performance was obtained when compared to flat, nanopillar and nanocone, and the mechanism behind was fully illustrated by analyzing the absorption profiles. Moreover, the NP arrays with rational design were successfully applied in hybrid SCs by employing organic hole-transporting poly (3,4-ethylene dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) on the top of the n-type c-Si, leading to simultaneously increase both in optical- and electro- properties. More results and explanations will be shown in a detailed way.