自组装分子由一个π-共轭单元和一个带侧链的锚定基团构成，在倒置钙钛矿太阳能电池中作为空穴选择接触层发挥着关键作用。目前的研究主要集中于通过调整自组装分子的侧链结构来提高器件性能。然而，自组装分子的π-共轭核心对器件性能和稳定性的影响仍然不明确。
近日，浙江大学薛晶晶教授和西湖大学王睿助理教授等人在Science China Materials发表研究论文，设计了一系列具有逐渐扩展的π-共轭结构的自组装分子，并探讨扩展π-共轭核心结构对自组装分子电子性质的影响。
本文要点
1) 随着自组装分子的π-共轭核心结构的延伸，发现器件性能显著提升，这主要归因于增强的空穴提取和传输。此外，π-共轭核心结构的扩展也增强了自组装分子之间的π-π相互作用，从而提高了钙钛矿电池的运行稳定性。2) 基于Py2分子的设计，成功实现了25.2%的光电转换效率，并显著提高了钙钛矿光伏器件的运行稳定性。Figure 1. Impact of extended π-conjugation on the electronic properties of PAH-based SAMs. (a) c-AFM images of ITO substrates coated with NaPA, AnPA, and Py1. (b) Theoretical models illustrating the assembly of NaPA, AnPA, and Py1 on the ITO substrate surface. (c) Calculated charge density differences along the vertical direction relative to the ITO substrate surface. (d) Energy levels of the assembled NaPA, AnPA, and Py1 films, as well as the perovskite film (unit of all energy levels: eV). (e) TRPL spectra of the perovskite films deposited on the assembled NaPA, AnPA, and Py1 films.![]()
Figure 2. Photovoltaic performance of PSCs based on NaPA, AnPA and Py1. (a) J-V curves of the best-performing PSC based on NaPA, AnPA and Py1. (b) Statistical distribution of PCE values derived from the J-V characteristics of PSCs based on NaPA, AnPA and Py1. (c) TPC measurements under the short-circuit condition for NaPA, AnPA, and Py1-based PSCs. (d) VOC as a function of illumination intensity for NaPA, AnPA, and Py1-based PSCs. (e) Evolution of PCEs tracked under continuous one-sun light soaking at ~35°C under open-circuit condition, following the ISOS-L-1 protocol.![]()
Figure 3. Electronic properties of Py2 and photovoltaic performance of Py2-based PSCs. (a) Structural representation of Py2, featuring further extended π-conjugation relative to Py1. (b) Surface current signals from ITO substrates coated with Py1 and Py2. (c) Energy levels of Py1 and Py2 films, as well as the perovskite film after contact (unit of all energy levels: eV). (d) J-V curves of the champion for the champion PSCs based on Py1 and Py2. (e) Stabilized PCE values for Py1 and Py2-based PSCs. (f) Statistical distribution of PCE values obtained from the J-V characteristics of PSCs incorporating Py1 and Py2.Figure 4. Enhanced device stability achieved by further extending the π-conjugation. (a) Evolution of PCEs monitored during continuous heating at ~85°C, in accordance with the ISOS-D-2 protocol. Maximum power point tracking of PSCs under continuous one-sun light soaking at ~35°C (b) and at ~55°C (c).Ke Zhao, Libing Yao, Chen Liu, Ilhan Yavuz, Jiahui Shen, Pengju Shi, Xu Zhang, Yixin Luo, Donger Jin, Yuan Tian, Sisi Wang, Wei Fan, Jiazhe Xu, Qingqing Liu, Xiaonan Wang, Liuwen Tian, Ruzhang Liu, Caner Değer, Rui Wang, Jingjing Xue. Tailoring the π-conjugation in self-assembled hole-selective molecules for perovskite photovoltaics. Sci. China Mater. (2024).https://doi.org/10.1007/s40843-024-3093-9
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