Electron transport layers (ETLs) are critical for improving device performance and stability of perovskite solar cells (PVSCs). Herein, a distannylated electron-deficient bithiophene imide (BTI-Tin) is synthesized, which enables us to access structurally novel acceptor–acceptor (A–A) type polymers. Polymerizing BTI-Tin with dibrominated naphthalene diimide (NDI-Br) and perylene diimide (PDI-Br) affords two A–A copolymers P(BTI-NDI) and P(BTI-PDI). The all-acceptor backbone yields both low-lying highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for the polymers, which combined with their high electron mobility render P(BTI-NDI) and P(BTI-PDI) as promising ETLs for perovskite solar cells (PVSCs). When applied as ETLs to replace the conventional [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) in planar p–i–n PVSCs, the PC₆₁BM-free devices based on P(BTI-NDI) and P(BTI-PDI) achieve remarkable power conversion efficiencies (PCEs) of 19.5% and 20.8%, respectively, with negligible hysteresis. Such performance is attributed to efficient electron extraction and reduced charge recombination. Moreover, the devices based on P(BTI-NDI) and P(BTI-PDI) ETLs show improved stability compared to the PC₆₁BM based ones due to the higher hydrophobicity of the new ETLs. This work provides important guidelines for designing n-type polymers to replace PC₆₁BM as efficient ETLs for high-performance PVSCs with improved stability.

中文翻译：

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酰亚胺官能化的受体-受体共聚物可作为高性能钙钛矿太阳能电池的有效电子传输层

电子传输层（ETL）对于改善钙钛矿型太阳能电池（PVSC）的性能和稳定性至关重要。在这里，合成了一个脱甲酰化的缺电子联噻吩亚胺（BTI-Tin），这使我们能够使用结构新颖的受体-受体（AA）类型的聚合物。将BTI-Tin与二溴化萘二酰亚胺（NDI-Br）和per二酰亚胺（PDI-Br）聚合，可得到两种A–A共聚物P（BTI-NDI）和P（BTI-PDI）。全受体主链可为聚合物产生低位的最高占据分子轨道（HOMO）和最低的未占据分子轨道（LUMO）能级，再加上它们的高电子迁移率使P（BTI-NDI）和P（BTI- PDI）作为钙钛矿太阳能电池（PVSC）的有前途的ETL。当用作ETL来代替常规[6,6]-苯基-C _61时平面p–i–n PVSC中使用聚丁酸甲酯（PC ₆₁ BM），基于P（BTI-NDI）和P（BTI-PDI）的无PC ₆₁装置实现了显着的功率转换效率（PCE）。磁滞可以忽略不计，分别为19.5％和20.8％。这种性能归因于有效的电子提取和减少的电荷复合。此外，与基于PC ₆₁ BM的设备相比，基于P（BTI-NDI）和P（BTI-PDI）ETL的设备显示出更高的稳定性，这是由于新ETL的疏水性更高。这项工作为设计n型聚合物以取代PC ₆₁ BM作为具有改进稳定性的高性能PVSC的有效ETL提供了重要指导。