PCBM与钙钛矿具有较好的界面相容性，有利于制备高性能器件。其具有显著的电子传递能力，可以有效地从钙钛矿层中提取电子，并且分子很容易聚集成大簇，降低了电子解离所需的界面面积。但是PCBM相对较低的电离势导致严重的电荷复合现象。此外其最低未占据分子轨道，与钙钛矿的功函之间的能级排列不是最优的，从而降低了器件性能。
基于上述问题，华中科技大学李雄教授团队和重庆大学臧志刚教授团队通过加入四甲基硫脲（TMDS）获得了更均匀的PCBM薄膜。经TMDS修饰的PCBM表面形貌分布均匀，几乎没有聚集，使PCBM完全覆盖在钙钛矿层上。在紫外光条件下，TMDS在溶液中容易形成高活性的还原性有机自由基，有利于经典电子受体PCBM的掺杂。
最终，目标设备的冠军PCE达到26.10%（认证为25.39%），而1cm²设备的PCE达到24.06%。在模拟am1.5照明下，经过1271小时的连续最大功率点跟踪（MPPT）后，目标器件的初始效率保持在95%以上。在85℃、85%相对湿度（RH）条件下老化1090h后，封装后的目标器件保持初始PCE的90%以上。TMDS修饰的PCBM在PSCs中表现出优异性能，明显改善电子萃取来显著抑制电荷复合效率，并且稳定性均优于传统PSCs。该研究对于提高倒置钙钛矿太阳能电池的性能和稳定性具有重要意义，有助于推动钙钛矿太阳能电池的工业化进程。
Fig. 1 | N doping effect and interactions. a PSCs structure and schematic illustration of chemical interactions between perovskite and TMDS or sulfur radicals.b Formation of sulfur radicals and n doping mechanism of PCBM. c Time-of-flight mass spectrum of PCBM with TMDS film. d The ESR spectra of different solutions.e XPS spectra of S 2p for TMDS and PCBM films without and with TMDS. XPS spectra of (f)S2p and (g) Pb 4 f, for TMDS and PVSK films without and with TMDS.h FTIR spectra of TMDS and PVSK films without and with TMDS.
Fig. 2 | Morphology and electrical properties. a, b AFM topography images and the (c) corresponding line profiles for PCBM films with and without TMDS treatment. d, e High-resolution top-view SEM images for PVSK/PCBM with and without TMDS. f The mobility of PCBM films with and without TMDS treatment. g, h KPFM surface potential images and the (i) corresponding line profiles for PCBM films with and without TMDS treatment.
Fig. 3 | Passivation and carrier transport. a Energy level diagram of the PCBM films without and with modifiers as well as perovskite film. b, c GIWAXS mappings of the perovskite films with and without TMDS treatment. d SCLC plots of the electron-only device ITO/SnO2/perovskite/PCBM/Ag where the PCBM films without and with TMDS were used. e, f PL mapping images of glass/perovskite without and with TMDS. g, h PL mapping images of the glass/perovskite/PCBM without and with TMDS. i PL and (j) TRPL spectra of the glass/perovskite without and with TMDS. k PL and (l) TRPL spectra of the glass/perovskite/PCBM without and with TMDS.
Fig. 4 | Photovoltaic Performance. a Forward and reverse scans of both the champion control and target PSCs were conducted to generate J-V curves, with relevant photovoltaic parameters depicted in the insets. b The J–V characteristics of the highest-performing target device, having a 1 cm2 surface area. c PCE histograms for PSCs with and without TMDS. Steady-state (d) current density and (e) PCE versus time for the best-performing devices measured at the maximum power point. f EQE spectra of the PSCs without and with TMDS. g The PCE of both the unencapsulated control devices and those modified with TMDS was assessed at the MPPT under sustained one-sun exposure within a chamber environment maintained at approximately 40 °C. h PCE of encapsulated devices accelerated aging at 85 °C and 85% relative humidity.
本文来源DOI:10.1038/s41467-024-53283-5
https://doi.org/10.1038/s41467-024-53283-5