Guo Songhao, Bu Kejun, Li Jiangwei, Hu Qingyang, Luo Hui, He Yihui, Wu Yanhui, Zhang Dongzhou, Zhao Yongsheng, Yang Wenge, Kanatzidis Mercouri G, Lü Xujie
Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China.
Key Lab of Organic Optoelectronics, Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China.
J Am Chem Soc. 2021 Feb 17;143(6):2545-2551. doi: 10.1021/jacs.0c11730. Epub 2021 Jan 19.
Pressure processing is efficient to regulate the structural and physical properties of two-dimensional (2D) halide perovskites which have been emerging for advanced photovoltaic and light-emitting applications. Increasing numbers of studies have reported pressure-induced and/or enhanced emission properties in the 2D halide perovskites. However, no research has focused on their photoresponse properties under pressure tuning. It is also unclear how structural change affects their excitonic features, which govern the optoelectronic properties of the halide perovskites. Herein, we report significantly enhanced photocurrents in the all-inorganic 2D perovskite CsPbICl, achieving over 3 orders of magnitude increase at the industrially achievable level of 2 GPa in comparison with its initial photocurrent. Lattice compression effectively regulates the excitonic features of CsPbICl, reducing the exciton binding energy considerably from 133 meV at ambient conditions to 78 meV at 2.1 GPa. Impressively, such a reduced exciton binding energy of 2D CsPbICl is comparable to the values of typical 3D perovskites (MAPbBr and MAPbI), facilitating the dissociating of excitons into free carriers and enhancing the photocurrent. Further pressurization leads to a layer-sliding-induced phase transition and an anomalous negative linear compression, which has not been observed so far in other halide perovskites. Our findings reveal the dramatically enhanced photocurrents in the 2D halide perovskite by regulating its excitonic features and, more broadly, provide new insights into materials design toward extraordinary properties.
压力处理对于调控二维（2D）卤化物钙钛矿的结构和物理性质是有效的，二维卤化物钙钛矿已在先进的光伏和发光应用中崭露头角。越来越多的研究报道了二维卤化物钙钛矿中压力诱导和/或增强的发光特性。然而，尚无研究关注其在压力调谐下的光响应特性。结构变化如何影响卤化物钙钛矿的激子特性（激子特性决定了卤化物钙钛矿的光电性质）也尚不清楚。在此，我们报道了全无机二维钙钛矿CsPbICl中光电流显著增强，在2 GPa这一工业可实现的压力水平下，与初始光电流相比，实现了超过3个数量级的增长。晶格压缩有效地调控了CsPbICl的激子特性，使激子结合能从环境条件下的133 meV大幅降低至2.1 GPa时的78 meV。令人印象深刻的是，二维CsPbICl如此降低的激子结合能与典型的三维钙钛矿（MAPbBr和MAPbI）的值相当，这有利于激子解离为自由载流子并增强光电流。进一步加压会导致层滑动诱导的相变和异常的负线性压缩，这在其他卤化物钙钛矿中尚未观察到。我们的研究结果揭示了通过调控二维卤化物钙钛矿的激子特性可显著增强其光电流，更广泛地说，为设计具有非凡性质的材料提供了新的见解。
