Two-dimensional (2D) perovskites are tailored-photoelectric-responsive materials owing to their lattice softness and designable multifunctional spacer cations. However, the inferior charge-carrier characteristics in these 2D systems are intolerable for photovoltaic devices. Here, we introduced a novelty spacer cation 3,3-difluoropyrrolidinium (DFP) to synthesize 2D Ruddlesden–Popper (RP) perovskite, (DFP)₂PbI₄. The multiple hydrogen bonds in the spacing region of (DFP)₂PbI₄ drive the structure toward uniqueness with the average Pb─I─Pb bond angles over 170°. This merit coupled with the large dipole moment of DFP demonstrates the unique bandgap (2.20 eV) and small exciton binding energies (99.76 meV) of (DFP)₂PbI₄. With the stacking of inorganic layers, the (DFP)₂MA₄Pb₅I₁₆ (MA⁺: CH₃NH₃⁺) film demonstrated an improved electron diffusion length (920 nm) and fast carrier extraction (0.73 μs) at the device level. The resultant (DFP)₂MA₄Pb₅I₁₆ solar cells achieved a champion power conversion efficiency (PCE) of 19.43%. Furthermore, the unencapsulated devices exhibited excellent stability under continuous illumination and persistent heating conditions.

中文翻译：

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优化太阳能电池用 2D Ruddlesden-Popper 钙钛矿的载流子特性

二维（2D）钙钛矿由于其晶格柔软性和可设计的多功能间隔阳离子而成为定制的光电响应材料。然而，这些二维系统中较差的载流子特性对于光伏器件来说是无法容忍的。在这里，我们引入了一种新颖的间隔阳离子3,3-二氟吡咯烷鎓（DFP）来合成2D Ruddlesden-Popper（RP）钙钛矿（DFP）₂ PbI ₄。 (DFP) ₂ PbI ₄间隔区的多个氢键驱动其结构趋于独特，平均Pb─I─Pb键角超过170°。这一优点与DFP的大偶极矩相结合，证明了(DFP) ₂ PbI ₄独特的带隙(2.20 eV)和小激子结合能(99.76 meV) 。通过无机层的堆叠，(DFP) ₂ MA ₄ Pb ₅ I ₁₆ (MA ⁺ : CH ₃ NH ₃ ⁺ ) 薄膜在器件中表现出改进的电子扩散长度 (920 nm) 和快速载流子提取 (0.73 μs)等级。所得的(DFP) ₂ MA ₄ Pb ₅ I ₁₆太阳能电池实现了19.43%的冠军功率转换效率(PCE)。此外，未封装的器件在连续照明和持续加热条件下表现出优异的稳定性。