Huang Yu-Hua, Wang Xu-Dong, Li Wen-Guang, Zou Su-Yan, Yang Xin, Kuang Dai-Bin
Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, LIFM, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou, 510275, China.
Small. 2024 Apr;20(15):e2306821. doi: 10.1002/smll.202306821. Epub 2023 Nov 27.
Low-dimensional perovskites afford improved stability against moisture, heat, and ionic migration. However, the low dimensionality typically results in a wide bandgap and strong electron-phonon coupling, which is undesirable for optoelectronic applications. Herein, semiconducting A-site organic cation engineering by electron-acceptor bipyridine (bpy) cations (2,2'-bpy and 4,4'-bpy) is employed to optimize band structure in low-dimensional perovskites. Benefiting from the merits of lower lowest unoccupied molecular orbital (LUMO) energy for 4,4'-bpy cation, the corresponding (4,4'-bpy)PbI is endowed with a smaller bandgap (1.44 eV) than the (CHNH)PbI (1.57 eV) benchmark. Encouragingly, an intramolecular type II band alignment formation between inorganic Pb-I octahedron anions and bpy cations favors photogenerated electron-hole pairs separation. In addition, a shortening distance between inorganic Pb-I octahedral chains in (4,4'-bpy)PbI single crystal (SC) can effectively promote carrier transfer. As a result, a self-powered photodetector based on (4,4'-bpy)PbI SC exhibits 131 folds higher on/off ratio (3807) than the counterpart of (2,2'-bpy)PbI SC (29). The presented result provides an effective strategy for exporting novel organic cation-based low-dimensional perovskite SC for high-performance optoelectronic devices.
低维钙钛矿具有更好的防潮、耐热和抗离子迁移稳定性。然而，低维度通常会导致宽带隙和强电子-声子耦合，这对于光电器件来说是不利的。在此，通过电子受体联吡啶（bpy）阳离子（2,2'-bpy和4,4'-bpy）进行的半导体A位有机阳离子工程被用于优化低维钙钛矿的能带结构。得益于4,4'-bpy阳离子较低的最低未占据分子轨道（LUMO）能量，相应的(4,4'-bpy)PbI的带隙（1.44 eV）比基准的(CHNH)PbI（1.57 eV）更小。令人鼓舞的是，无机Pb-I八面体阴离子与bpy阳离子之间形成的分子内II型能带排列有利于光生电子-空穴对的分离。此外，(4,4'-bpy)PbI单晶（SC）中无机Pb-I八面体链之间距离的缩短可以有效地促进载流子转移。结果，基于(4,4'-bpy)PbI SC的自供电光电探测器的开/关比（3807）比(2,2'-bpy)PbI SC的对应物（29）高131倍。所呈现的结果为输出用于高性能光电器件的新型有机阳离子基低维钙钛矿SC提供了一种有效策略。
