Simultaneous improvement of Jsc, Voc and FF of polymer solar cells with CuI as hole transport layer

A novel buffer layer copper iodide (CuI) was introduced into PCDTBT, PC70BM polymer solar cells (PSCs), where the CuI acts simultaneously as of hole transport layer (HTL) and electron block layer (EBL). Through depositing the CuI between the polymer and Ag and Au anodes, the hole collection ability has been increased. By optimizing the thickness of CuI and top anode, simultaneous enhancement of short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) has been achieved, leading to a dramatic increase of device efficiency, from 0.67% to 5.47% with 3 nm CuI and Au anode in comparison with the device without CuI. With thicker CuI, the efficiency decreases noticeably both for Au and Ag anodes due to the block effect. The result indicates that the CuI is an effective buffer layer for PCDTBT, PC70BM PSCs.