Fluolab【Angew.Chem.】郑州大学郭玮|效率突破26.5%！深共晶电解质策略攻克钙钛矿太阳能电池稳定性难题
文章标题： Lithium-Based Deep Eutectic in Spiro-OMeTAD Enable Efficient and Stable Perovskite Solar Cells
通讯作者： Wei Guo
文章概要
引言
钙钛矿太阳能电池（PSCs）作为一种极具潜力的光伏技术，其效率的提升很大程度上依赖于在空穴传输材料Spiro-OMeTAD中添加锂盐（LiTFSI）和叔丁基吡啶（tBP）。然而，传统的锂盐掺杂存在严重的锂离子迁移和吸湿性问题，这不仅会导致空穴传输层出现气泡状空洞，还会破坏钙钛矿层的完整性，从而严重限制器件的长期工作寿命。为了平衡高效率与长寿命，寻找一种能有效固定锂离子并修复薄膜缺陷的新型掺杂策略成为了当前光伏领域的研究热点。
The multi-site interaction and deep eutectic characteristics of DpyDS with Li+. (a) ESP images of DpDS, DpyDS, BpyDS, and tBP. (b) Binding energies of DpDS-Li+, DpyDS-Li+, BpyDS-Li+, tBP-Li+, and H2O-Li+. (c) 7Li NMR of LiTFSI, LiTFSI-DpDS, LiTFSI-H2O, LiTFSI-BpyDS, LiTFSI-tBP, and LiTFSI-DpyDS. (d and e) Raman spectra of DpyDS, LiTFSI-DpyDS, and LiTFSI. (f) The radial distribution function and coordination numbers of DpyDS:LiTFSI = 1:1 molar ratio. (g) Representative solvation structure from molecular dynamics simulation.
主要实验及结论
研究团队创新性地引入了一种双齿配位分子2,2'-联吡啶二硫醚（DpyDS）。实验发现，DpyDS能与传统的LiTFSI在室温下自发形成一种液态深共晶混合物（Deep Eutectic Mixture）。这种深共晶网络具有强大的分子间相互作用，能够像“锚”一样将活跃的锂离子牢牢固定在空穴传输层中，从根本上抑制了锂离子向钙钛矿内部的破坏性扩散。
Characterization of Spiro-OMeTAD doped with DpyDS. (a) Conductivities, (b) hole mobilities, and (c) UV–vis absorption spectra of Spiro-OMeTAD, Spiro-DpDS, Spiro-DpyDS, and Spiro-BpyDS. (d) Spiro-OMeTAD·+ EPR spectra of Spiro-OMeTAD, Spiro-DpDS, Spiro-DpyDS, and Spiro-BpyDS. (e) Energy levels of the perovskite, Spiro-OMeTAD, Spiro-DpDS, Spiro-DpyDS, and Spiro-BpyDS. (f) Time-resolved photoluminescence spectra of perovskite, perovskite/Spiro-OMeTAD, perovskite/Spiro-DpDS, perovskite/Spiro-DpyDS, and perovskite/Spiro-BpyDS. (g) AFM images and surface potential images of perovskite/Spiro-OMeTAD, perovskite/Spiro-DpDS, perovskite/Spiro-DpyDS, and perovskite/Spiro-BpyDS. (h) Surface potential distributions of the measured contact potential difference of Spiro-OMeTAD, Spiro-DpDS, Spiro-DpyDS, and Spiro-BpyDS.
更具突破性的是，由于这种混合物在常温下呈液态，它赋予了空穴传输层独特的自修复功能。这种液态分子膜能够自发填充并修复因tBP挥发或环境因素产生的微孔和空隙，构建出更加致密且无孔的薄膜结构。在光电性能方面，DpyDS与锂离子的强配位作用促进了TFSI-离子的解离，显著增强了Spiro-OMeTAD的空穴迁移率和导电率。这不仅加快了空穴的提取速度，还大幅降低了非辐射复合损失。
Characterization of reduced migration pathways and suppressed ion migration. Conductive AFM images of (a) the control and (b) target samples with and without aging (48 h at 65°C and 30% RH). (c and d) Current of the diagonal line scan in (a) and (b). SEM images of (e) the control and (f) target with and without aging. (g) ToF-SIMS depth profiles of Li+, Pb+, and Au+ ions in the ITO/ETL/perovskite/HTL/Au structure under the control (short dot) and target (solid), after being subjected to thermal stress at 65°C and 30% RH for 120 h. (h) Nyquist plot of LiTFSI and LiTFSI-DpyDS. (i) Schematic diagram of the stable HTL after DpyDS doping.
得益于这一策略，实验制备的钙钛矿器件实现了高达26.53%的光电转换效率（PCE），并获得了26.37%的正式认证效率，这一数值在同类器件中处于领先水平。在稳定性测试中，未封装的器件在最大功率点连续运行1800小时后，依然能够维持初始效率的90.5%，展现出卓越的耐环境老化能力。
Transport properties and photovoltaic performance of the device. (a) Plots of as a function of light intensity for the without (control) and with DpyDS (target) devices. (b) IMVS measurement of the control and target devices. (c) IMPS measurement of the control and target devices. (d) J-V curves from forward and reverse scans of the control device and the target device. Control-reverse is abbreviated as Control-R; Control-Forward is abbreviated as Control-F. (e) PCE statistics of the control and target devices. (f) EQE spectra and integrated of the control and target devices.
Long-term stability of the device. (a) Humidity stability of the unencapsulated PSCs in a dark environment at ∼30% relative humidity. (b) Thermal stability of the unencapsulated PSCs stored under 65°C in a dark nitrogen glove box. (c) MPPT of the unencapsulated PSCs at 25°C in N2 atmosphere. (d) MPPT of the unencapsulated PSCs at 65°C in N2 atmosphere.
总结及展望
这项研究成功验证了深共晶策略在优化空穴传输层性能方面的巨大潜力。通过精细的分子设计，DpyDS不仅解决了掺杂剂的迁移与吸湿难题，还利用液态成膜特性实现了薄膜的物理修复。这一成果不仅为高性能、长寿命钙钛矿太阳能电池的商业化路径提供了新的技术方案，也为其他有机光电器件的功能化掺杂提供了极具参考价值的理论指导。