[2.2]Paracyclophane-based hole-transporting materials for perovskite solar cells

To develope an alternative efficient hole-transporting materials (HTMs) to 2,2',7,7',-tertrakis(N,N-p-dimethox-yphenylamino)-9,9'-spirobifuorene (spiro-OMeTAD) for high performance perovskite solar cells (PSCs), we demonstrate a series of donor-pi-donor HTMs (WS-1, WS-2, and WS-4 HTMs) with [2.2]paracyclophane ([2.2] PCP) as the core structure and triphenylamine as four arms at pseudo-para and pseudo-ortho orientations. Compared with the well-known HTM of spiro-OMeTAD, WS-HTMs has a simpler synthetic route and short synthesis steps (3-4 steps). Due to the improved hole mobility and good charge transfer efficiency of pseudo-para- [2.2]PCP HTMs (WS-1 and WS-2), the out-of-plane carrier transport is enhanced and the PSC base on WS-1/WS-2 HTMs achieve higher J(sc) and ff values than the device based on pseudo-ortho-[2.2]PCP HTM (WS-4). A SnO2 electron transport layer (ETL) with WS-1 HTM shows the best power conversion efficiency of 19.13% in a PSC, which is higher than that of spiro-OMeTAD (17.71%) under the same conditions. The WS-HTMs also provided better stability and moisture resistance in PSCs, which prolongs the lifetime in the ambient environment than in case of spiro-OMeTAD.

Automated summary

This study demonstrates that using novel WS-HTMs instead of spiro-OMeTAD can enhance the performance of perovskite solar cells, with devices based on WS-1 and WS-2 HTMs showing better power conversion efficiency and stability. By improving hole mobility and charge transfer efficiency, WS-HTMs achieved good results.