[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-dimethoxyphenylamino)-9,9′-spirobifuorene (spiro-OMeTAD) for high performance perovskite solar cells (PSCs), we demonstrate a series of donor-π-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.