Wang Ti, Fu Yongping, Jin Linrui, Deng Shibin, Pan Dongxu, Dong Liang, Jin Song, Huang Libai
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.
School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China.
J Am Chem Soc. 2020 Sep 23;142(38):16254-16264. doi: 10.1021/jacs.0c04377. Epub 2020 Sep 9.
Understanding semiconductor surface properties and manipulating them chemically are critical for improving their performance in optoelectronic devices. Hybrid halide perovskites have emerged as an exciting class of highly efficient solar materials; however, their device performance could be limited by undesirable surface properties that impede carrier transport and induce recombination. Here we show that surface functionalization of methylammonium lead iodide (MAPbI) perovskite with phenethylammonium iodide (PEAI), a commonly employed spacer cation in two-dimensional halide perovskites, can enhance carrier diffusion in the near-surface regions and reduce defect density by more than 1 order of magnitude. Using transient transmission and reflection microscopy, we selectively imaged the transport of the carriers near the (001) surface and in the bulk for single-crystal MAPbI microplates. The surface functionalization increases the diffusion coefficient of the carriers in the 40 nm subsurface region from ∼0.6 cm s to ∼1.0 cm s, similar to the value for bulk carriers. These results suggest the PEA ligands are effective in reducing surface defect and phonon scattering and shed light on the mechanisms for enhancing photophysical properties and improving solar cell efficiency.
了解半导体表面特性并对其进行化学调控对于提高其在光电器件中的性能至关重要。混合卤化物钙钛矿已成为一类令人兴奋的高效太阳能材料；然而，其器件性能可能会受到不良表面特性的限制，这些特性会阻碍载流子传输并引发复合。在此，我们表明，用碘化苯乙铵（PEAI，二维卤化物钙钛矿中常用的间隔阳离子）对甲基碘化铅（MAPbI）钙钛矿进行表面功能化，可以增强近表面区域的载流子扩散，并将缺陷密度降低超过1个数量级。利用瞬态透射和反射显微镜，我们对单晶MAPbI微板的（001）表面附近和体相中载流子的传输进行了选择性成像。表面功能化使40 nm次表面区域中载流子的扩散系数从约0.6 cm²/s增加到约1.0 cm²/s，与体相载流子的值相似。这些结果表明，PEA配体在减少表面缺陷和声子散射方面是有效的，并揭示了增强光物理性质和提高太阳能电池效率的机制。
