Highly efficient organic solar cells based on a robust room-temperature solution-processed copper iodide hole transporter

Solution-processed copper(I) iodide (CuI) is demonstrated to be an effective hole transporting layer (HTL) for several polymer:fullerene bulk heterojunction (BHJ) systems, leading to demonstration of efficiency up to 8.8% in the standard device configuration and in many cases surpassing the performance of devices based on PEDOT:PSS as HTL.