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Replacing the dominated hole transport material (HTM), doped Spiro-OMeTAD, in state-of-the-art perovskite solar cells (PSCs) is a challenge but an urgent issue for commercialization of this technology. Here, a solution-processable two-dimensional (2D) polymer HTM, namely, 2DP-TDB, which featuring with extended π-electron delocalization into the two-dimensions, has been successfully developed. It is found that 2DP-TDB shows multifunctional characteristics, such as dominant face-on packing orientation, good charge transport properties, efficient perovskite surface passivation capability. and hydrophobicity. As a result, planar n-i-p structured PSCs employing 2DP-TDB as dopant-free HTM exhibit a high efficiency of 21.53%, which is much larger than that using a control 2D small molecule (TB-DPP) (11.61%). Importantly, after further optimization of the perovskite film with the formamidine-based spacer, the devices based on dopant-free 2DP-TDB HTM show a champion efficiency as high as 22.17%. This work offers a fundamental strategy by developing 2D conjugated polymer HTMs for dopant-free PSCs with both high efficiency and stability.
Fu et al. (Fri,) studied this question.