An asymmetrically substituted dithieno[3,2-b:2',3'-d]pyrrole organic small-molecule hole-transporting material for high-performance perovskite solar cells

Hole-transporting materials play a vital role in terms of the performance of perovskite solar cells (PSCs). The dithieno[3,2-b:2',3'-d]pyrrole (DTP), an S,N-heterocyclic building block, has been proved to be desirable for molecular design of hole-transporting materials in PSCs. We developed an asymmetrically substituted DTP small-molecule (JW12) and a reference compound (JW11). The asymmetrical structure of JW12 leads to different absorption properties and electron distribution. The device in a planar n-i-p architecture using JW12 shows a much higher PCE (18.07%) than that based on JW11 (15.46%), which is also better than the device based on spiro-OMeTAD (17.47%). We hope our research can provide a new perspective in molecular design of organic HTMs for perovskite solar cells.