【JACS】协同钝化新突破：26.19%光电转换效率，解锁钙钛矿太阳能电池寿命密码
文章标题：Selective Bidentate Coordination Reconstructs Residual PbI2 to Homogenize Interfacial Energetics in Perovskite Solar Cells
通讯作者：Artem Musiienko, Brett M. Savoie, Letian Dou
文章概要
该研究针对金属卤化物钙钛矿太阳能电池中因残留碘化铅导致的界面能量学不均匀及光生复合损失问题，提出了一种全新的双齿螯合钝化策略。通过精心设计含硫代吩基团的双齿铵盐配体，研究团队成功实现了在不破坏底层三维钙钛矿晶格的前提下，选择性地将残留的层状碘化铅重构为空间均匀、电子相干的八面体晶格框架。这一策略大幅降低了电池的非辐射复合损失，使反式结构电池获得了高达26.19%的光电转换效率，并在连续光照与高温加速老化测试中表现出极为优异的长期运行稳定性。
引言
金属卤化物钙钛矿太阳能电池作为下一代光伏技术的核心代表，其光电转换效率在过去几年里取得了突飞猛进的增长。然而，如何实现工业级标准的长期运行稳定性依然是阻碍其商业化落地的关键瓶颈。在钙钛矿薄膜的结晶过程中，为了提升薄膜质量和钝化缺陷，通常需要引入过量的碘化铅。但这把“双刃剑”在界面处的非均匀聚集和光降解行为，会诱发剧烈的局部电势波动，形成严重的非辐射复合中心。传统的单齿配体或强极性溶剂钝化方法由于作用力较弱或极易破坏底层三维钙钛矿结构，无法从根本上消除这种界面能量学的空间异质性。因此，开发一种既能选择性修复残留碘化铅，又能构建空间高度均匀且稳定的电子界面的化学调控策略，对于制备高效稳定的光伏器件具有至关重要的科学意义。
Figure 1. Molecular design and passivation mechanism of mono- and bidentate ligands. (a) Molecular structures and electrostatic potential maps of ligands. (b) Schematic images and simulated adsorption energies of PEA and MeX on PbI2 surfaces. UV–vis absorption spectra (c) and PL spectra (d) measured by dissolving PbI2 and ligands into a mixed solvent (CB/IPA; v/v = 9:1). The inset of (d) is the schematic image of ligand-encapsulated PbI6 unit in mixed solvent (CB/IPA; v/v = 9:1). (e) Surface Pb/I ratio of treated films determined by XPS. (f) Schematic showing different passivation routes. Color scheme for atomic representations used throughout: hydrogen (white), carbon (black), nitrogen (blue), oxygen (red), sulfur (yellow), iodine (light pink), and lead (orange).
主要实验及结论
为了直观揭示双齿配体与碘化铅之间独特的作用机制，研究团队首先通过分子设计对比了传统单齿配体与新型双齿配体对碘化铅的界面重构行为。分子静电势分布和理论计算表明，引入富电子硫原子的噻吩基双齿配体表现出更强的路易斯酸碱相互作用和极高的吸附能。如图1所示，光谱表征进一步证实，在非共轭溶剂体系中，双齿配体能够表现出极强的配位能力，成功将原本不溶的碘化铅高效分散并将其诱导转化为具有典型二维特征的 corner-sharing 碘化铅八面体配合物。光电子能谱分析更进一步表明，经双齿配体处理后的薄膜表面铅碘比显著降低，证实其并非简单地洗去残留物质，而是通过化学重构将其转变为类似于钙钛矿结构的稳定骨架，从而形成了完全不同于单齿配体的选择性钝化路径。
Figure 2. Strong and spatially uniform PbI2 coordination enabled by bidentate ligands. (a) Schematic of ligand soaking and spin coating. (b) OM images showing 2D fluorescence contrast at the middle vs the edge. (c) Energy-level alignment of ligand-treated films extracted from UPS, including WF and Highest Occupied Molecular Orbital (HOMO)/Valence Band Maximum (VBM) onset. (d) Fluorescence images of ligand-treated PbI2 films. (e, f) CPD maps from KPFM (e) and TRSPV transients (f) for ligand-treated PbI2 films. The inset in (f) illustrates the SPV probing configuration at the ligand-PbI2 interface. (g) FTIR spectra of ligand-PbI2 films. (h) GIWAXS 2D patterns of PbI2-MeX and PbI2-MeXT films. Scale bars: 20 μm (panel d) and 2 μm (panel e).
这种微观重构反应在宏观薄膜尺度上展现出了惊人的空间均匀性。如图2所示，光学显微镜与荧光成像技术清晰地表明，传统的单齿配体由于反应动力学过快，极易在薄膜边缘或局部区域发生严重的异质聚集，导致严重的荧光不均匀性；而双齿配体则实现了覆盖全膜的高度空间均一荧光分布。开尔文探针力显微镜和瞬态表面光电压技术进一步量化了这种电子表面能级的优化。双齿配体钝化使整块薄膜的接触电势差空间涨落降至最低，整体功函数明显下移，转化为更为优异的n型电子接触界面。同时，薄膜表面的电子陷阱态被完全中和，这为抑制器件界面处的非辐射复合、大幅提升开路电压奠定了坚实的物质基础。
Figure 3. Selective passivation of surface PbI2 on FAPbI3 by bidentate ligands. (a–c) Top-view SEM images (a), KPFM contact potential difference (CPD) maps (b), and SPV spatial maps (c) of pristine and ligand-treated FAPbI3 films. In panel (a), the insets highlight representative regions where large plate-like crystallites are observed atop the underlying 3D FAPbI3 grains in monodentate-treated films. The CPD maps in (b) display the surface potential distribution (mV), while the SPV maps in (c) show the normalized photoinduced surface potential amplitude (a.u.), where brighter regions correspond to stronger local photoresponse. (d) Quantified CPD, CPD variation, and amplitude variation of ligand-passivated FAPbI3 films. (e) TRSPV transients of ligand-passivated FAPbI3 films. (f) TRPL measurements of ligand-passivated FAPbI3 films. Scale bars: 2 μm (panels a and b); 1 μm (the inset of panel a); 5 mm (panel c).
当将该策略直接应用于真实的甲脒基钙钛矿薄膜表面时，双齿配体的选择性重构优势得到了完美的体现。如图3所示，扫描电镜和空间电势成像表明，原始钙钛矿表面富集的碘化铅颗粒在经双齿配体处理后，实现了形态学上的温和重组与能级均匀化，同时完全避免了单齿配体极易引发的晶格溶蚀和深层形态劣化。角度依赖的掠入射广角X射线散射进一步证明了其在多个晶面方向上均实现了各向同性的高效钝化。得益于这种完美的界面修复，薄膜的荧光寿命从原始的201纳秒大幅提升至437纳秒，充分证实了非辐射复合通道被成功斩断，电荷提取效率获得了质的飞跃。
Figure 4. Device performance and nonradiative loss analysis. (a) TRSPV transients of ligand-passivated FAPbI3 films incorporated with hole transport layer. (b) Schematic of the n-i-p device architecture illustrating enhanced hole extraction at the perovskite/HTL interface, consistent with the increased SPV response in (a). (c) PCE statistical distribution. All boxes display the mean value, with 1.5× outlier range whiskers. (d) J–V curves of the champion devices with different ligand passivation. (e) Nonradiative _V_oc components from EQE plots. (f) _V_oc vs light intensity plots of devices with different ligand passivation. (g, h) Stability of PTAA-based devices under ISOS-L1 (OC, light) (g) and ISOS-L2 (75 °C, OC) (h). Initial PCEs (control/MeX/MeXT) are 18.97/21.08/21.75% in (g) and 16.91/21.18/20.50% in (h), respectively.
总结及展望
综上所述，该项工作突破了传统单齿配体钝化存在的高空间异质性和晶格破坏性局限，利用双位点锚定螯合效应在钙钛矿光伏界面构筑了电子coherent且热力学稳定的保护层。如图4所示，将此策略融入正式结构器件后，电池展现出了极低的非辐射电压损失，理想因子趋近于完美的辐射复合极限，从而创造了26.19%的优异单节效率纪录。更令人振奋的是，该器件在经历1500小时的持续运行以及在75摄氏度高温加速老化1000小时后，仍能保持初始效率的80%以上，为解决残留碘化铅引发的光热不稳定问题提供了兼具理论突破与实用价值的普适性宏观调控方案。