Stable Formamidinium‐Based Centimeter Long Two‐Dimensional Lead Halide Perovskite Single‐Crystal for Long‐Life Optoelectronic Applications
Rajesh Kumar Ulaganathan, C. M. Raghavan, Chang‐Yu Lin, Ambika Subramanian, Weiliang Chen, Yu‐Ming Chang, Alex Rozhin, Raman Sankar
Abstract
Abstract Solution‐processable 2D metal‐halide perovskites are highly promising for cost‐effective optoelectronic applications due to their intrinsic multiquantum well structure. However, the lack of stability is still a major obstacle in the use of this class of materials in practical devices. Here, the authors demonstrate the stable optoelectronic properties using formamidinium (FA)‐based centimeter‐long 2D perovskite (BA) 2 FAPb 2 I 7 high‐quality single‐crystal controlled by the thickness of two perovskite layers. The large area single‐crystal exhibits good crystallinity, phase purity, and spectral uniformity. Moreover, the (BA) 2 FAPb 2 I 7 single‐crystal shows excellent stability at open atmospheric conditions when compared to methylammonium (MA)‐based (BA) 2 MAPb 2 I 7 counterparts. The photodetectors fabricated using 2D perovskite single‐crystal on the rigid Si/SiO 2 substrate reveal high photoresponsivity ( R λ )(≈5 A W −1 ), the fast response time (<20 ms), specific detectivity ( D *) (≈3.5 × 10 11 Jones), and excellent durability under 488 nm laser illumination. The R λ and D * values are obtained from the (BA) 2 FAPb 2 I 7 single‐crystal 25 times and three orders magnitudes, respectively, higher than the (BA) 2 MAPb 2 I 7 single‐crystal. Additionally, the perovskite material on flexible polymer substrate reveals good photo‐sensing properties in both bending and nonbending states.