Symmetry-Broken 2D Lead–Tin Mixed Chiral Perovskite for High Asymmetry Factor Circularly Polarized Light Detection

Symmetry-Broken 2D Lead−Tin Mixed Chiral Perovskite for High Asymmetry Factor Circularly Polarized Light Detection Bing Yao,⊥Qi Wei,⊥Yunqing Yang,⊥Wenjia Zhou, Xianyuan Jiang, Hao Wang, Mingyu Ma, Danni Yu, Yingguo Yang, and Zhijun Ning*,⊥ Cite This: Nano Lett. 2023, 23, 1938−1945 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Symmetry-broken-induced spin splitting plays a key role for selective circularly polarized light absorption and spin carrier transport. Asymmetrical chiral perovskite is rising as the most promising material for direct semiconductor-based circularly polarized light detection. However, the increase of asymmetry factor and extension of response region remain to be a challenge. Herein, we fabricated a two-dimensional tin−lead mixed chiral perovskite with tunable absorption in the visible region. Theoretical simulation indicates that the mixing of the tin and lead in chiral perovskite breaks the symmetry of the pure ones, resulting in pure spin splitting. We then fabricated a chiral circularly polarized light detector based on this tin−lead mixed perovskite. A high asymmetry factor for the photocurrent of 0.44 is achieved, which is 144% higher than pure lead 2D perovskite, and it is the highest value reported for the pure chiral 2D perovskite-based circularly polarized light detector using a simple device structure. KEYWORDS: symmetry broken, tin−lead mixed perovskite, CPL detector, spin polarization, chiral perovskite T he direct circularly polarized light (CPL) detection is a promising strategy in early stage disease detection, drug screening, security surveillance, and optical communication with better sensitivity and resolution compared to indirect systems.1−3 However, materials with a high asymmetrical factor of light absorption and excellent electrical properties simultaneously are rare. Traditional inorganic semiconductors show excellent electrical properties; however, it is difficult to include intrinsic chirality in them.4 Plasmonic−nanostructure arrays show excellent circularly polarized light selection; however, the absorbance is low, and the device fabrication remains a challenge, especially large-scale devices.5,6 In recent years, hybrid perovskite materials consisting of organic chiral molecules and an inorganic framework provide new freedom for circularly polarized light detection.7−9 In combination with symmetry restriction endowed by organic chiral molecules and excellent semiconductor properties from the inorganic framework, chiral hybrid perovskite provides an ideal material for the construction of a direct circularly polarized light detector.10−12 A photodetector based on chiral perovskite shows an unprecedented high asymmetrical factor.13 To enhance device performance, significant efforts are made to improve circularly polarized absorption such as molecular engineering,14,15 dimensionality manipulation,16−18 and nano- structure engineering. A large circular dichroism asymmetrical factor of 0.49 for the perovskite metasurface with super- structural chirality is reported.19 However, current chiral 2D perovskite CPL detectors based on general simple structures are still showing a limited asymmetrical factor below 0.31.20 Despite that one-dimensional or zero-dimensional perovskites show a higher asymmetrical factor, the response region is limited to the UV area.1,21 Meanwhile, the two-dimensional perovskite generally presents higher conductivity that is beneficial for extraction of carriers produced by CPL absorption. The asymmetry factor of the photocurrent in the CPL detector is not only related to the circularly polarized absorption but also associated with the circularly polarized transport of carriers in chiral materials, which is related to the spin splitting.22 Spin lifetime is another important factor that determines the spin transport.23 Recent investigation suggests that tin perovskite shows a much longer spin lifetime due to the wea