Perovskite (PEA)2Pb(I1-xBrx)4 single crystal thin films for improving optoelectronic performances

Abstract Single crystal perovskites have become advanced materials in many applications due to their excellent optoelectronic properties and stability. However, bulk single crystal with unsatisfactory thickness would limit its application in flexible optoelectronic devices. Here, large-area two-dimensional perovskite (PEA)2Pb(I1-xBrx)4 (x = 0–1) single crystal thin films (SCTFs) were prepared with a space-confined solution temperature-lowering crystallization method. Through rational control of halide compositions, we succeeded in growing (PEA)2Pb(I1-xBrx)4 SCTFs with x increased from 0 to 1, which achieved band gap fine-tuning from 2.28 to 2.95 eV, corresponding to the edge of the absorption spectrum adjusted from green to blue. Using the excellent (PEA)2Pb(I1-xBrx)4 SCTFs properties, a series of photodetectors were designed. The photodetector based on the I-rich composition (x = 0.1) exhibits optimum photosensitivity (Ilight/Idark = 2 × 104) at wavelength of 473 nm (0.52 mW cm−2), while the photodetector based on the Br-rich component (x = 0.8) has the highest Ilight/Idark ratio (~1.6 × 104) under 405 nm (0.52 mW cm−2), showing the selectivity in light detection. At the same time, those devices show extremely low dark current, high specific detectivity (~1013 Jones) and excellent stability.