Organic−inorganic hybrid perovskites have become one of the most promising thin-film solar cell materials owing to their remarkable photovoltaic properties. However, nonradiative recombination of carriers usually leads to inferior performance of perovskite (PVK) devices. Interface modification is one of the effective ways to improve separation of charges for perovskite solar cells (PSCs). Here, a small organic molecule of tetrafluorophthalonitrile (TFPN) is used to enhance the extraction and transportation of carriers at the PVK/hole transport layer (HTL) interface. The electron-rich C−F group effectively reduces the trap state density in the perovskite through chemical combination with the empty orbital of Pb 2+ or other electron traps on the PVK surface, resulting in enhanced interface contact between the PVK and HTL. Meanwhile, the CN group in TFPN also inactivates the defects caused by Pb 2+ . The Fermi level of the perovskite shifts by 0.15 eV to its valence band due to the strong electron acceptor nature of the F atom, indicating that positive dipoles and p-type doping emerge, which validly suppress the recombination of carriers for the PVK film. Therefore, the optimized PSC shows the highest power conversion efficiency (PCE) of 22.82% compared to 19.40% for the control one. The champion FF reaches up to 81.2% (PCE 21.44%) due to the effectively enhanced carrier separation. In addition, the unencapsulated device shows enhanced stability under air conditions.

Intrinsic defects are key factors that would affect the performance and stability of perovskite solar cells (PSCs). Herein, a sulfonamides additive, methyl 3‐sulfamoyl‐2‐thiophenecarboxylate (MSTC), is introduced into the PbI2 or FAI/MACl/MABr precursor solution, to prepare high‐quality PSCs with a two‐step method. After the addition of MSTC, all the devices show enhanced performance. With optimized MSTC incorporated into PSCs, the champion power conversion efficiency (PCE) of the PSCs is increased from 19.19% to 22.14%, and the stability is also improved. The MSTC‐FAI based device can still maintain 89% of its initial PCE compared to 68% of the control one after 15 days in ambient condition under relative humidity of 40–50% at room temperature in dark. Test results reveal that amido group in MSTC would coordinate with PbI2 or FAI through hydrogen bonding (NH···I), thus effectively enhancing the performance of devices. Nevertheless, the sulfonyl and carbonyl groups in MSTC would coordinate with the FAI precursor through chemical bond of COS and COC. And with the hydrogen bonding connection between MSTC and FAI, the inherent defects in the MSTC‐FAI based device are effectively suppressed, leading to the enhanced photovoltaic performance.

Perovskite defect passivation with molecule doping shows great potential in boosting the efficiency and stability of perovskite solar cells (PSCs). Herein, an efficient and low-cost bifunctional Lewis base additive d-tryptophan is introduced to control the crystallization and growth of perovskite grains and passivation defects. It is found that the additive doped in the solution precursors could retard crystal growth by increasing activation energy, resulting in improved crystallization of large grains with reduced grain boundaries, as well as inhibiting ion migration and PbI2 aggregation. As a result, the PSCs incorporated with d-tryptophan additives achieve an improved power conversion efficiency from 18.18 to 21.55%. Moreover, the d-tryptophan passivation agent improves the device stability, which retains 86.85% of its initial efficiency under ambient conditions at room temperature after 500 h. This work provides Lewis base small-molecule d-tryptophan for efficient defect passivation of the grain boundaries toward efficient and stable PSCs.

The crystallinity of perovskite films is crucial for the performance and stability of perovskite solar cells (PSCs). Defects usually emerge in grain boundaries, leading to decomposition and non-radiative recombination of PSCs. Here, we present an effective additive engineering strategy to augment the long-term operation and stability of PSCs by doping a molecule with a symmetrical structure and bifunctional passivation, 2,5-thiophene dicarboxylic acid (TDCA), into the precursor solution. It is demonstrated that TDCA coordinates with the perovskite through hydrogen and Pb–O bonding, resulting in significantly enhanced crystallinity and defect passivation such as uncoordinated Pb2+ and I–. Meanwhile, the grain size is increased from 350 nm to about 650 nm for the perovskite, as well as the grain boundaries are reduced, which could inhibit the carrier non-radiative recombination loss. Consequently, the power conversion efficiency of champion PSCs is promoted from 19.31 to 22.78%. Furthermore, the enhanced crystallinity and defect passivation improve the wet-thermal stability of PSCs.

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