【Adv.Mater.】中科大肖正国、程位任、杨上峰、段昌奎、佟宇|26.54%效率与卓越稳定性兼得！聚合表面钝化突破性成果
文章标题：Polymerized Surface Passivation for Stable and Efficient Inverted Perovskite Solar Cells
通讯作者：Yu Tong, Changkui Duan, Shangfeng Yang, Weiren Cheng, Zhengguo Xiao
文章概要
引言
溶液法制备的钙钛矿薄膜表面不可避免地会产生卤化物空位和未配位的金属离子等表面缺陷，这严重制约了钙钛矿太阳能电池的效率与长效稳定性。尽管传统的有机铵盐小分子表面钝化策略在提升效率上取得了显著进展，但这类小分子在持续光照和热应力下极易发生脱质子、解吸或分解，导致钝化层失效并加速器件衰减。为了打破这一瓶颈，研究团队创新性地提出了一种可聚合表面钝化策略，利用同时含有不饱和乙烯基和膦酸基团的乙烯基膦酸（VPA）作为钝化材料。在低热退火下，VPA可在钙钛矿表面原位聚合成强大的网络结构，不仅增强了与钙钛矿表面的附着力，还形成了一道抵御环境水氧侵害的坚固屏障。
Polymerized surface passivation of perovskite films. (a) Schematic illustration of the limitations of PEAI as a passivation layer. (b,c), Schematic illustrations of VPA monomers (b) and PVPA (c) on the perovskite surface. (d,f) 1H NMR (d), 13C NMR (e), and FTIR spectra (f) of PVPA. (g) Binding energies of VPA and three configurations of PVPA on the perovskite surface. The binding energy is evaluated as the energy required for molecular attachment. (h) Crystal structures of perovskite surface passivated with PVPA through DFT calculations. (i) The molecular structure of PVPA configuration on top of the perovskite surface.
主要实验及结论
研究人员将乙烯基膦酸单体旋涂于钙钛矿薄膜表面，通过轻微热处理成功诱导其原位聚合为聚乙烯基膦酸（PVPA）。通过核磁共振与红外光谱测试，明确证实了乙烯基向单键碳氢链的转化及聚合反应的发生。理论计算与光电表征进一步表明，PVPA的膦酸基团与表面未配位的金属铅离子形成了强烈的共价配位键，有效修复了表面陷阱态，使非辐射复合得到显著抑制，载流子寿命从原本的六百多纳秒大幅提升至两千多纳秒。同时，均匀覆盖的聚合物钝化层改善了界面能级匹配，大幅促进了电荷的提取与输运。
Characterizations of the perovskite films. (a), Electrostatic potential (ESP) map of PEAI, and PVPA; µ represents the dipole moment of the molecule. (b,c), Steady-state (b) and time-resolved (c) photoluminescence (PL) spectra of perovskite films with and without PEAI or PVPA treatment. The lifetimes for each trace were calculated using a bi-exponential decay model. (d), C-AFM measurements of the perovskite samples under 1 V bias. All potential and current mappings were obtained under ambient light.
基于这种独特的聚合钝化层，团队成功构建了高性能反式钙钛矿太阳能电池。实验结果表明，经过PVPA处理的器件实现了高达26.54%的光电转换效率，并获得了26.24%的第三方权威认证效率，开路电压达到惊人的1.19伏。更为卓越的是器件的长期运行稳定性，在室温及连续一太阳光照下进行最大功率点跟踪测试，未封装的电池在运行1600小时后仍能保持初始效率的90%以上。即使在60摄氏度的加速老化环境下，器件在经历700小时后依然能够维持90%的稳健性能，展现出远超传统小分子钝化器件的热稳定性。
Device performance characterizations of PSCs. (a) Schematic illustration of the device structure. (b) Current density–voltage (J–V) curves of control, PEAI-, and PVPA-passivated devices. (c) J–V characteristics of the best-performing PVPA-based device certified at the National Photovoltaic Industry Measurement and Testing Center (NPVM). The reverse and forward scans are both included. (d) Photovoltaic parameter statistics of the control, PEAI-, and PVPA-treated PSCs. More than ten devices were measured under each condition. (e) The stabilized power output of the PVPA-passivated device under one sun illumination. (f) EQE of EL of the devices operated as LEDs. (g) Light-intensity-dependent _V_OC variation and linear fitted slope. (h–j) Transient photovoltage (TPV) (h), transient photocurrent (TPC) (i), and fitted electrochemical impedance spectroscopy (EIS) (j) curves of the control, PEAI-, and PVPA-treated devices.
Stability studies of perovskite films and devices. (a) Photographs of the bare perovskite films stored in ambient air: Room temperature with a relative humidity of ∼60%. (b) Steady PL stability of perovskite films. The average temperature and humidity during the test period were recorded. Error bars are included from three independent measurements, but are smaller than the marker size and therefore not clearly visible. (c,d) MPP stability tracking of unencapsulated control, PEAI-, and PVPA-passivated devices under simulated 1-sun illumination at room temperature (c) and 60°C (d), respectively.
总结及展望
这项工作成功论证了聚合表面钝化策略在攻克钙钛矿太阳能电池稳定性和效率双重难题上的巨大潜力。PVPA通过强大的共价交联网络和牢固的化学配位，完美解决了传统小分子钝化剂易脱附、易分解的致命缺陷，为实现产业化所需的长期运行寿命开辟了新途径。未来的研究可以沿着这一方向继续深化，通过探索具有更高聚合度、更强配位能力的全新可聚合钝化剂，并全面评估其在湿度、高温以及反向偏压等更复杂恶劣工况下的耐受性，从而进一步加速钙钛矿光伏技术的商业化量产进程。