Effects of post-annealing on the property of CsPbBr3 films and the performance of relevant light-emitting diodes

All-inorganic metal halide perovskite materials have attracted considerable attention in display and lighting fields due to their excellent photoelectric properties. It has been found that post treatment, especially post-annealing process generally plays crucial roles in promoting the crystal quality and properties of the perovskite films, as well as the performance of the relevant devices, but the promotion mechanism has not been reached thoroughly yet. Herein, we successfully synthesized the CsPbBr3 perovskite films through dual-source co-evaporation of CsBr and PbBr2 by applying the molecular beam epitaxy (MBE) technique in an ultrahigh vacuum system. The effects of post-annealing on the structure and optical property were systematically studied for the films, and the optimal post-annealing condition was determined to be 90 °C for 10 min. As the characterization results by SEM, XRD, PL, etc., shown, the optimizing effect is attributed to the size change and the quality enhancement of the CsPbBr3 microcrystals in the films with temperature. Using CsPbBr3 films as the emitting layers, the perovskite light-emitting diodes (PeLEDs) with the configuration of ITO/PVK/CsPbBr3/TPBi/LiF/Al were constructed with the optimized emitting layer of 200 nm. The device shows pure green emission at a wavelength of 527 nm with a narrow full width at half-maximum of 19 nm. The post-annealing optimized device achieved an external quantum efficiency (EQE) of 1.6 % along with a maximum luminance of 39,700 cd/m2, which represents a significant improvement over the device consisting of unannealed CsPbBr3 film, with the EQE increased by 1.6 times and the luminance increased by 4.7 times. •Our paper mainly includes the following points:•The CsPbBr3 films were successfully prepared through dual-source co-evaporation of CsBr and PbBr2 by applying the MBE technique in an UHV system.•The systematic investigations strongly confirmed that the post-annealing treatment significantly enhances the optical property of CsPbBr3 film by improving its crystal quality, and the optimal post-annealing condition was determined to be 90 °C for 10 min.•Using CsPbBr3 films as the EMLs, we applied the PeLEDs with the structure of ITO/PVK/CsPbBr3/TPBi/LiF/Al to achieve green electroluminescence with a wavelength of 527 nm and a FWHM of 19 nm.•Under the optimal EML thickness of 200 nm and post-annealling condition, the PeLED with the CsPbBr3 EML obtained an EQE of 1.6 % and a maximum luminance of 39,700