Abstract Electron transport layer (ETL) of perovskite solar cells (PSCs) plays an important role on transferring electrons from perovskite layer to transparent conductive oxide layer, strongly affecting PSC performance. In the present study, effects of adding graphene quantum dots (GQDs) as a dopant to the mesoscopic TiO2 (mp-TiO2) ETL on performance of a PSC were investigated. Different amounts (1.25, 2.5 and 5 vol%) of GQDs were directly added to the TiO2 precursor solution which was subsequently applied as the doped ETL by spin coating. The results showed that Jsc, Voc and FF of the 2.5 vol% GQDs-doped cell were 21.92 mA/cm2, 0.97 V and 0.63, respectively, corresponding to a PCE of 14.36% (champion cell), approximately 50% improvement compared to the un-doped cells (best PCE 9.55%). The perovskite film in the GQDs-doped cell was dense with fewer pinholes which facilitated electron extraction, and accelerated charge mobility in TiO2 layer, consequently promoting Jsc and Voc. Based on EIS results, GQDs doping into the TiO2 ETL significantly suppressed the recombination processes, resulting in a higher FF. Interestingly, the PSC based on 2.5 vol% GQDs-doped TiO2 ETL maintained ~88% of its initial PCE (champion cell), after 500 h under ambient conditions; whereas, the conventional PSC based on pure TiO2 ETL maintained only 61% of its initial PCE under the same conditions, suggesting a dramatic improvement in the device stability. The findings clearly showed that GQDs doping to TiO2 ETL could be a potential and confident approach for improving performance and stability of the mesoscopic PSCs.

中文翻译：

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具有 GQDs 掺杂 TiO2 电子传输层的介观钙钛矿太阳能电池的性能增强

摘要 钙钛矿太阳能电池 (PSC) 的电子传输层 (ETL) 在将电子从钙钛矿层转移到透明导电氧化物层中起着重要作用，强烈影响 PSC 的性能。在本研究中，研究了在介观 TiO2 (mp-TiO2) ETL 中添加石墨烯量子点 (GQD) 作为掺杂剂对 PSC 性能的影响。将不同量（1.25、2.5 和 5 vol%）的 GQD 直接添加到 TiO2 前体溶液中，随后通过旋涂将其作为掺杂 ETL 应用。结果表明，掺杂 2.5 vol% GQDs 的电池的 Jsc、Voc 和 FF 分别为 21.92 mA/cm2、0.97 V 和 0.63，对应于 14.36%（冠军电池）的 PCE，与原电池相比提高了约 50%。未掺杂的电池（最佳 PCE 9.55%）。GQDs 掺杂电池中的钙钛矿薄膜致密，针孔较少，有助于电子提取，并加速 TiO2 层中的电荷迁移率，从而促进 Jsc 和 Voc。根据 EIS 结果，掺杂到 TiO2 ETL 中的 GQD 显着抑制了复合过程，从而导致更高的 FF。有趣的是，在环境条件下 500 小时后，基于 2.5 vol% GQDs 掺杂的 TiO2 ETL 的 PSC 保持了其初始 PCE（冠军电池）的约 88%；而基于纯 TiO2 ETL 的传统 PSC 在相同条件下仅保持其初始 PCE 的 61%，表明器件稳定性有了显着提高。研究结果清楚地表明，掺杂到 TiO2 ETL 中的 GQD 可能是提高介观 PSC 性能和稳定性的一种潜在且可靠的方法。