RESUMO
All-inorganic lead halide perovskite, characterized by its exceptional optical and electrical properties, is burgeoning as a potential optoelectronic material. However, the standalone CsPbBr3 component encounters several challenges including small exciton binding energy (≈40 meV) and long charge diffusion length, giving rise to low photo-luminescence quantum-yield (PLQY); ion migration leads to instability in device operation, hindering device operation and potential development. To circumvent these limitations, our research endeavors to construct a novel core-shell structure that transforms the continuous [PbX6]4- octahedron into an isolated octahedral structure. We introduce the Cs4PbBr6 phase with 0D structure to passivate the vacancy defects in CsPbBr3, thereby suppressing ion migration and enhancing the luminescence intensity and stability. Our methodology involves fabricating dense CsPbBr3-Cs4PbBr6 composite films using a co-evaporation method, wherein the molar ratio of CsBr and PbBr2 is precisely adjusted. The films are subsequently rapidly annealed under ambient air conditions, and the effects of different annealing temperatures and annealing times on the CsPbBr3-Cs4PbBr6 films were investigated. Our results demonstrate significantly improved stability of the annealed films, with a mere 15% decrease in PL intensity after 100 days of storage under ambient air conditions at 48% relative humidity (RH). Based on this thin film, we fabricated all-inorganic structure Ag/N-Si/CsPbBr3-Cs4PbBr6/NiO/ITO light emitting diodes (LEDs), the devices have a low turn-on voltage VT â¼3 V and under unencapsulated, ambient air conditions, it can operate continuously for 12 hours under DC drive with only 10% attenuation. The results we obtained open up the possibility of designing and developing air-stable perovskite LEDs.
RESUMO
The all-inorganic lead halide perovskite has become a very promising optoelectronic material due to its excellent optical and electrical properties. Device performances are currently hindered by crystallinity of the films and environmental stability. Here, we adopted dual-source co-evaporation method to prepare CsPbBr3 films. By adjusting and controlling the co-evaporation ratio and substrate temperature, we obtained CsPbBr3 films with large grain sizes and uniform morphology. Films with smooth surfaces and large grains exhibit properties such as efficient photon capture, fast carrier transport, and suppressed ion migration. Therefore, in this paper, by refining the annealing conditions, the effects of annealing temperature and time on the films were studied in detail. The CsPbBr3 films were annealed under suitable annealing temperature and time in ambient air, and films with high quality and crystallinity and average grain size up to ~ 2.5 µm could maintain stability in ambient air for 130 days. The corresponding LEDs show the full width at half maximum (FWHM) of the green EL spectrum is as narrow as 18 nm, and the devices have a low turn-on voltage VT ~ 3 V and can work continuously for 12 h in ambient air.