美国西北大学Edward H. Sargent团队在Science期刊发表题为“Amidination of ligands for chemical and field-effect passivation stabilizes perovskite solar cells”的研究论文，团队成员杨熠、陈昊、刘成为论文第一作者，Edward H. Sargent & Mercouri G. Kanatzidis & Bin Chen为共同通讯作者。

核心亮点：本文开发了一种用于场效应和化学钝化的脒基配体库，脒基配体的N-H键因共振效应而增强，能够有效抵抗脱质子化，从而显著提升钙钛矿表面钝化层的热稳定性。这种策略导致配体去质子化平衡常数降低 10 倍以上，在85°C空气照射下老化后的光致发光量子产率维持率提高了2倍。通过实施这种方法，实现了倒置PSCs的认证准稳态PCE26.3%；并在85°C空气环境下连续运行1100小时后，PCE保持率≥90%，性能稳定。

近年来，钙钛矿太阳能电池（PSCs）发展迅速，钙钛矿太阳能电池（PSCs）。推动这一进步的关键因素是表面钝化技术的实施，包括使用低维钙钛矿、芳香胺和铵配体。然而，当前最先进的PSCs使用有机铵配体来解决表面缺陷问题并减少钙钛矿-电荷传输层界面处的非辐射复合。虽然不同种类的铵类配体可以实现化学和场效应钝化，但铵类配体也倾向于脱质子成挥发性胺和卤素，特别是在光和热应力下。铵去质子化会导致钝化效果的丧失，并在设备长时间运行过程中在钙钛矿膜表面产生空位缺陷，从而降低器件在长期运行过程中的稳定性。

针对这一问题，研究团队提出在化学和场效应钝化剂中，将头部基团从铵改为脒基，可以解决高温下每类分子去质子化引起的不稳定性问题，以提升PSCs表面钝化层的热稳定性。该策略将配体的去质子化平衡常数降低了十倍以上，并使钙钛矿薄膜在85°C光照老化后的光致发光量子产率保持率提升了两倍。通过实施这种方法，研究人员实现了倒置PSCs的认证准稳态PCE26.3%；并在85°C空气环境下连续运行1100小时后，PCE保持率≥90%，性能稳定。

该研究表明，将钝化配体的锚定基团从铵改为脒基可阻止配体去质子化，并延长钝化层在高温下的稳定性，同时保持钝化效果。研究团队认为配体的脒化与扩展的功能相结合，是开发下一代钝化策略的一个极具潜力的方向，有望进一步提高高效钙钛矿光电器件的耐久性。

Fig. 1. Stability of amidinium ligands. (A) Molecular structures of ligands used in this study. (B) The N–H dissociation energies (E_D) of ammonium ligands and their corresponding amidinium ligands obtained by DFT calculations and acid dissociation constant (pK_a) values measured by titration of a 0.05 N ligand solution with 0.05 N NaOH. (C) PCE comparison of PSCs using different ligand passivation. Twelve devices were evaluated at each condition, and data are presented as mean ± standard deviation.

Fig. 2. Stability of amidinium passivation layers. (A) N 1s XPS depth profile of fresh and aged perovskite films treated with PDAI₂ and PDII₂, and F 1s depth profile of fresh and aged perovskite films treated with 4FBAI and 4FBII. The white color represents the highest intensity, while the red and blue represent the lowest intensity. (B) ToF-SIMS of C₃H₁₂N₂ ²⁺, C₇H₉FN⁺, C₃H₁₀N4²⁺, and C₇H₈FN²⁺ for fresh and aged perovskite films treated with PDAI₂, PDII₂, 4FBAI, and 4FBII, respectively. a.u., arbitrary units. 

Fig. 3. Passivation effect of amidinium ligands. (A) The electron density in the conduction band (n) near the surface of perovskite films with different treatments. (B) TRPL spectra of perovskite films with different treatments. (C) PLQY of the control, PDAI₂/3MTPAI-based, and PDII₂/4FBII-based perovskite films with and without C₆₀ deposition. (D) PLQY of the control, PDAI₂/3MTPAI-based, and PDII₂/4FBII-based perovskite films without C₆₀ before and after aging under 85°C, 1-sun-equivalent light illumination, and 50% RH in air. 

Fig. 4. Device performance. (A) Cross-sectional SEM image of the device structure. (B) PCE statistics for control, PDAI₂/3MTPAI-passivated, and PDII₂/4FBII-passivated devices. The center line indicates the median, the box limits represent the upper and lower quartiles, the whiskers denote the minimum and maximum values, and the vertical curved lines illustrate the data distribution. (C) Current density–voltage (J-V) curves of the best PDII₂/4FBII-passivated device. (D) The stabilized power output of the PDII₂/4FBII-passivated device. (E) MPP stability tracking of glass-encapsulated devices under 1-sun illumination at 85°C under 50% RH in air. 

本文来源：DOI: 10.1126/science.adr2091