In this work, the ultrafast transient absorption spectroscopy (TAs) was utilized to first investigate the charge transfer from the emerging FAPbI₃ (FA = CH(NH₂)₂) perovskite quantum dots (PQDs) to charge transport layers. Specifically, we compared the TAs in pure FAPbI₃ PQDs, PQDs grown with both electron and hole transfer layers (ETL and HTL), and PQDs with only ETL or HTL. The TA signals induced by photoexcited electrons decay much faster in PQDs samples with the ETL (~20 ps) compared to the pure FAPbI₃ PQDs (>1 ns). These results reveal that electrons can effectively transport between coupled PQDs and transfer to the ETL (TiO₂) at a time scale of 20 ps, much faster than the bimolecular charge recombination inside the PQDs (>1 ns), and the electron transfer efficiency is estimated to be close to 100%. In contrast, the temporal evolution of the TA signals in the PQDs with and without HTL exhibit negligible change, and no substantive hole transfer to the HTL (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], PTAA) occurs within 1 ns. The much slower hole transfer implies the further potential of increasing the overall photo-carrier conversion efficiency through enhancing the hole diffusion length and fine-tuning the coupling between the HTL and PQDs.

中文翻译：

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从CH（NH2）2PbI3钙钛矿量子点到电荷传输层的对比电子和空穴传输动力学

在这项工作中，超快瞬态吸收光谱（TAs）用于首先研究从新兴的FAPbI ₃（FA = CH（NH ₂）₂）钙钛矿量子点（PQDs）到电荷传输层的电荷转移。具体来说，我们比较了纯FAPbI ₃ PQD ，带有电子和空穴传输层（ETL和HTL）的PQD ，以及仅带有ETL或HTL的PQD的TA 。与纯FAPbI ₃ PQDs （> 1 ns）相比，在具有ETL的PQDs样品中，由光激发电子诱导的TA信号衰减快得多（〜20 ps ）。这些结果表明，电子可以有效地在耦合的PQD之间传输并转移到ETL（TiO ₂）在20 ps的时间尺度上，比PQD内部（> 1 ns）的双分子电荷复合要快得多，并且电子传输效率估计接近100％。相比之下，有无HTL的PQD中TA信号的时间变化变化很小，并且没有大量空穴转移至HTL（聚[双（4-苯基）（2,4,6-三甲基苯基）胺]， PTAA）在1 ns内发生。较慢的空穴传输意味着通过增加空穴扩散长度和微调HTL与PQD之间的耦合来提高整体光电载流子转换效率的潜力。