Su Hang, Xu Zhuo, He Xilai, Yao Yuying, Zheng Xinxin, She Yutong, Zhu Yujie, Zhang Jing, Liu Shengzhong Frank
Dalian National Laboratory for Clean Energy, iChEM, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, P. R. China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
Adv Mater. 2024 Jan;36(2):e2306724. doi: 10.1002/adma.202306724. Epub 2023 Nov 29.
The abundant oxygen-related defects (e.g., O vacancies, O-H) in the TiO electron transport layer results in high surface energy, which is detrimental to effective carrier extraction and seriously impairs the photovoltaic performance and stability of perovskite solar cells. Here, novel surface energy engineering (SEE) is developed by applying a surfactant of heptadecafluorooctanesulfonate tetraethylammonium (HFSTA) on the surface of the TiO . Theoretical calculations show that the HFSTA-TiO is less prone to form O vacancies, leading to lower surface energy, thus improving the carrier-extraction efficiency. The experimental results show that superior perovskite film is obtained due to the reduced heterogeneous nucleation sites and improved crystallization process on the modified TiO . Furthermore, the flexible long alkyl chains in HFSTA considerably relieve the compressive stresses at the buried interface. By combining the passivation of TiO , crystallization process modulation, and stress relief, a champion PCE up to 25.03% is achieved. The device without encapsulation sustains 92.2% of its initial PCE after more than 2500 h storage under air ambient with relative humidity of 25-30%. The SEE of a buried interface paves a new way toward high-efficiency, stable perovskite solar cells.
二氧化钛电子传输层中大量与氧相关的缺陷（如氧空位、O-H）导致表面能较高，这不利于有效的载流子提取，并严重损害钙钛矿太阳能电池的光伏性能和稳定性。在此，通过在二氧化钛表面施加十七氟辛烷磺酸四乙铵（HFSTA）表面活性剂，开发了一种新型表面能工程（SEE）。理论计算表明，HFSTA修饰的二氧化钛不易形成氧空位，导致表面能降低，从而提高了载流子提取效率。实验结果表明，由于修饰后的二氧化钛上异质形核位点减少且结晶过程得到改善，因此获得了优异的钙钛矿薄膜。此外，HFSTA中灵活的长烷基链大大缓解了掩埋界面处的压应力。通过结合二氧化钛的钝化、结晶过程调控和应力缓解，实现了高达25.03%的最佳功率转换效率（PCE）。在相对湿度为25-30%的空气环境中储存超过2500小时后，未封装的器件保持其初始PCE的92.2%。掩埋界面的表面能工程为高效、稳定的钙钛矿太阳能电池开辟了一条新途径。
