Hunan Key Laboratory of Super-microstructure and Ultrafast Process, Hunan Key Laboratory of Nanophotonics and Devices, Institute of Super-microstructure and Ultrafast Process in Advanced Materials (ISUPAM), School of Physics and Electronics, Central South University, Changsha, Hunan, 410083, P. R. China.
State Key Laboratory of Powder Metallurgy, Powder Metallurgy Research Institute, Central South University, Changsha, Hunan, 410083, P. R. China.
Small. 2023 Jun;19(25):e2207848. doi: 10.1002/smll.202207848. Epub 2023 Mar 17.
Polyvinyl pyrrolidone (PVP) is doped to PbI and organic salt during two-step growth of halideperovskite. It is observed that PVP molecules can interact with both PbI and organic salt, reduce the aggregation and crystallization of the two, and then slow down the coarsening rate of perovskite. As doping concentration increases from 0 to 1 mM in organic salt, average crystallite size of perovskite decreases monotonously from 90 to 34 nm; Surface fluctuation reduces from 259.9 to 179.8 nm at first, and then increases; Similarly, surface roughness decreases from 45.55 to 26.64 nm at first, and then rises. Accordingly, a kind of "confinement effect" is resolved to crystallite growth and surface fluctuation/roughness, which helps to build compact and uniform perovskite film. Density of trap states (t-DOS) is cut down by ≈60% at moderate doping (0.2 mM). Due to the "confinement effect", power conversion efficiency of perovskite solar cells is improved from 19.46 (±2.80) % to 21.50 (±0.99) %, and further improved to 24.11% after surface modification. Meanwhile, "confinement effect" strengthens crystallite/grain boundaries and improves thermal stability of both film and device. T of device increases to 120 h, compared to 50 h for reference ones.
聚乙烯吡咯烷酮（PVP）在两步法生长卤化物钙钛矿过程中被掺杂到 PbI 和有机盐中。研究发现，PVP 分子可以同时与 PbI 和有机盐相互作用，减少两者的聚集和结晶，从而减缓钙钛矿的粗化速率。随着掺杂浓度从 0 增加到 1mM 的有机盐中，钙钛矿的平均晶粒尺寸从 90nm 单调减小到 34nm；表面波动先从 259.9nm 减小到 179.8nm，然后增加；同样，表面粗糙度先从 45.55nm 减小到 26.64nm，然后上升。因此，一种“限制效应”被解决到晶体生长和表面波动/粗糙度，这有助于构建致密和均匀的钙钛矿薄膜。在适度掺杂（0.2mM）时，陷阱态密度（t-DOS）减少了约 60%。由于“限制效应”，钙钛矿太阳能电池的功率转换效率从 19.46%（±2.80%）提高到 21.50%（±0.99%），经过表面修饰后进一步提高到 24.11%。同时，“限制效应”增强了晶粒/晶界的稳定性，提高了薄膜和器件的热稳定性。器件的 T 增加到 120h，而参考器件的 T 为 50h。
