Enhancing light absorption for organic solar cells using front ITO nanograting and back ultrathin Al layer* *Project supported by the Natural Science Foundation of Gansu Province, China (Grant No. 20JR10RA611) and the Fundamental Research Funds for Central Universities, China (Grant Nos. lzujbky-2017-178 and lzujbky-2017-181).

Abstract

To address the discrepancy between carrier collection and light absorption of organic solar cells caused by the limited carrier mobility and optical absorption coefficient for the normally employed organic photoactive layers, a light management structure composed of a front indium tin oxide (ITO) nanograting and ultrathin Al layer inserted in between the photoactive layer and the electron transport layer (ETL) is introduced. Owing to the antireflection and light scattering induced by the ITO nanograting and the suppression of light absorption in the ETL by the inserted Al layer, the light absorption of the photoactive layer is significantly enhanced in a spectral range from 400 nm to 650 nm that also covers the main energy region of solar irradiation for the normally employed active materials such as the P3HT:PC61BM blend. The simulation results indicate that comparing with the control device with a planar configuration of ITO/PEDOT:PSS/P3HT:PC61BM (80-nm thick)/ZnO/Al, the short-circuit current density and power conversion efficiency of the optimized light management structure can be improved by 32.86% and 34.46%. Moreover, good omnidirectional light management is observed for the proposed device structure. Owing to the fact that the light management structure possesses the simple structure and excellent performance, the exploration of such a structure can be believed to be significant in fabricating the thin film-based optoelectronic devices.