中科院福建物质结构研究所罗军华团队报道了用于自驱动X射线探测的厘米级无铅（BA）2CsAgBiBr7/Cs2AgBiBr6异质晶体的原位外延生长策略。相关研究成果发表在2021年11月30日出版的《美国化学会杂志》。

卤化物钙钛矿异质晶体是由不同的钙钛矿单晶组成，在基础研究和应用器件设计中都引起了极大的兴趣。使用该异质晶体的一个关键优势是其内置电势，增强了固态器件中的电荷传输并抑制了噪声。基于该战略，高性能光电器件（如X射线探测器）已成功得到展示。然而，该异质晶体中金属阳离子（Pb）的毒性阻碍了它们的广泛应用。因此，开发无铅卤化物钙钛矿型异质晶体具有重要意义，但仍然极具挑战性。

该文中，研究人员报告了一种溶液处理原位异质外延方法，该方法创建了第一个无铅卤化物钙钛矿型异质晶体，（BA）2CsAgBiBr7/CS2AGIBR6（BA=正丁基铵），尺寸高达10×7×6 mm³。所生长的异质晶体具有高的结晶质量，并且存在近原子尖锐的界面。更令人兴奋的是，（BA）2CsAgBiBr7/Cs2AgBiBr6异质结能够在结中形成内置电势，从而触发自发电荷分离/传输。因此，使用异质晶体的X射线探测器可以在自驱动模式下工作，并显示出比原始CS2AgBiB6晶体探测器更高的灵敏度（206μC Gy^–1 cm^–2）、超低暗电流和操作稳定性。研究发现首次证明了无铅卤化物钙钛矿型异质晶体，并可能为大量可持续的小型钙钛矿型光电器件提供机会。

附：英文原文

Title: In Situ Epitaxial Growth of Centimeter-Sized Lead-Free (BA)2CsAgBiBr7/Cs2AgBiBr6 Heterocrystals for Self-Driven X-ray Detection

Author: Xinyuan Zhang, Tingting Zhu, Chengmin Ji, Yunpeng Yao, Junhua Luo

Issue&Volume: November 30, 2021

Abstract: Halide perovskite heterocrystals, composed of distinct perovskite single crystals, have generated great interest for both fundamental research and applied device designs. One of the key advantages of using such a heterocrystal is its built-in electric potential, which enhances charge transport and suppresses the noise in the solid-state devices. On the basis of this strategy, high-performance optoelectronic devices (e.g., X-ray detectors) have been successfully demonstrated. However, the toxicity of metal cations (Pb) in those reported heterocrystals hinders their wider applications. Thus, developing lead-free halide perovskite heterocrystals is significant but remains highly challenging. Here, we report a solution-processed in situ heteroepitaxial approach that enables us to create the first lead-free halide perovskite heterocrystal, (BA)2CsAgBiBr7/Cs2AgBiBr6(BA = n-butylammonium), with dimensions of up to 10 × 7 × 6 mm3. The as-grown heterocrystals have high crystalline quality and present near atomically sharp interfaces. More excitingly, the (BA)2CsAgBiBr7/Cs2AgBiBr6 heterogeneous integration allows the formation of a built-in electric potential in the junction, which triggers spontaneous charge separation/transport. Consequently, X-ray detectors using the heterocrystals can operate in a self-driven mode and exhibit an impressive sensitivity (206 μC Gy–1 cm–2) superior to that of the pristine Cs2AgBiBr6 crystal detectors, an ultralow dark current, and operational stability. Our findings provide the first demonstration of lead-free halide perovskite heterocrystals and may open up opportunities for a host of sustainable and miniaturized perovskite optoelectronic devices.

DOI: 10.1021/jacs.1c08959

Source: https://pubs.acs.org/doi/10.1021/jacs.1c08959