Enhancing Light Absorption for Organic Solar Cells Using a Front ITO Nanograting and Back Ultrathin Al layer

Abstract

To address the contradiction between carrier collection and light absorption of organic solar cells because of 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. Thanks to antireflection and light scattering induced by the ITO nanograting and suppression of light absorption in the ETL by the inserted Al layer, light absorption of the photoactive layer is significantly enhanced in the spectral range of 400 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, compared 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 can be improved by 32.86% and 34.46% after incorporating the optimized light management structure. Moreover, good omnidirectional light management is observed for the proposed device structure. Given the simple structure and excellent performance, this study is therefore believed to provide valuable exploration of light management structures for thin film-based optoelectronic devices.