High-performance and durable perovskite solar cells (PSCs) have advanced rapidly, enabled in part by the development of superior interfacial hole-transporting layers (HTLs). Here, a new series of 2,3-diphenylthieno [3,4-b]pyrazine (DPTP)-based small molecules containing bis-and tetrakis-triphenyl amino donors (1−3) was synthesized from simple, low-cost, and readily available starting materials. The matched energy levels, ideal surface topographies, high hole mobilities of 8.57 × 10 −4 cm 2 V −1 S −1 , and stable chemical structures of DPTP-4D (3) make it an effective hole-transporting material, delivering a PCE of 20.18% with high environmental, thermal, and light-soaking stability when compared to the reference HTL materials, doped Spiro-OMeTAD and PTAA in PSC n-i-p planar devices. Overall, these DPTP-based molecules are promising HTM candidates for the fabrication of stable PSCs.

A new set of pyrrolopyrrole‐based (PPr) polymers incorporated with thioalkylated/alkylated bithiophene (SBT/BT) is synthesized and explored as hole‐transporting materials (HTMs) for Sn‐based perovskite solar cells (TPSCs). Three bithiophenyl spacers bearing the thioalkylated hexyl (SBT‐6), thioalkylated tetradecyl (SBT‐14), and tetradecyl (BT‐14) chains are utilized to examine the effect of the alkyl chain lengths. Among them, the TPSCs are fabricated using PPr‐SBT‐14 as HTMs through a two‐step approach by attaining a power conversion efficiency (PCE) of 7.6% with a remarkable long‐term stability beyond 6000 h, which has not been reported elsewhere for a non‐PEDOT:PSS‐based TPSC. The PPr‐SBT‐14 device is stable under light irradiation for 5 h in air (50% relative humidity) at the maximum power point (MPP). The highly planar structure, strong intramolecular S(alkyl)···S(thiophene) interactions, and extended π‐conjugation of SBT enable the PPr‐SBT‐14 device to outperform the standard poly(3‐hexylthiophene,‐2,5‐diyl (P3HT) and other devices. The longer thio‐tetradecyl chain in SBT‐14 restricts molecular rotation and strongly affects the molecular conformation, solubility, and film wettability over other polymers. Thus, the present study makes a promising dopant‐free polymeric HTM model for the future design of highly efficient and stable TPSCs.

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Improving perovskite film quality is essential for making solar cells with enhanced performance. A critical bottleneck for progress in perovskite solar cell science is the lack of a scalable coating method that can be used for industrial manufacturing. This study investigated the combined cooperation of methylammonium acetate (MAAc) additive doping in a perovskite precursor solution and a mixed nonfullerene small-molecule semiconductor additive (DCDTT) in chlorobenzene for an antisolvent spraying treatment for the preparation of an ultrasonic spray-coated perovskite film. This spray-coating method forms densely arranged crystals and passivates the defect states located around the surface grain boundaries through additive engineering. The additives form an MAAc-based intermediate and DCDTT coordination interaction with Pb 2+ , increasing the film quality of the methylammonium lead iodide (MAPbI 3 ) perovskite. It was found that the addition of MAAc together with the antisolvent DCDTT treatment contributed to the enhanced crystallinity and reduced grain boundaries and trap states in perovskite films. These attributes result in a markedly higher power conversion efficiency (PCE) of 17.18% in the corresponding inverted perovskite solar cell than in the control device, with a PCE of 10.04%. The synergetic additive-modified perovskite devices retain ∼85% of the initial PCE after 7 days under ambient conditions. These observations point to a passivating effect by introducing additives while using a scalable spraying method for depositing perovskite films.

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