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.

中文翻译：

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用于自驱动 X 射线检测的厘米级无铅 (BA)2CsAgBiBr7/Cs2AgBiBr6 异晶的原位外延生长

卤化物钙钛矿异晶由不同的钙钛矿单晶组成，引起了基础研究和应用器件设计的极大兴趣。使用这种异晶的主要优势之一是其内置电势，可增强电荷传输并抑制固态器件中的噪声。在此策略的基础上，高性能光电设备（例如，X 射线探测器）已被成功展示。然而，这些报道的异晶中金属阳离子（Pb）的毒性阻碍了它们的更广泛应用。因此，开发无铅卤化物钙钛矿异晶具有重要意义，但仍然极具挑战性。在这里，我们报告了原位处理的解决方案异质外延方法使我们能够创建第一个无铅卤化物钙钛矿异晶，(BA) ₂ CsAgBiBr ₇ /Cs ₂ AgBiBr ₆ (BA =正丁基铵)，尺寸高达 10 × 7 × 6 mm ³。生长的异晶具有高结晶质量并存在于原子级锐界面附近。更令人兴奋的是，(BA) ₂ CsAgBiBr ₇ /Cs ₂ AgBiBr ₆异质集成允许在结中形成内置电势，从而触发自发的电荷分离/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运行，并表现出令人印象深刻的灵敏度 (206 μC Gy ^–1 cm ^–2 )，优于原始的 Cs ₂ AgBiBr ₆晶体探测器、超低暗电流、和运行稳定性。我们的研究结果首次展示了无铅卤化物钙钛矿异晶，并可能为大量可持续和小型化的钙钛矿光电器件开辟机会。