RESUMO
Realization of electrically pumped laser diodes based on solution-processed semiconductors is a long-standing challenge. Metal halide perovskites have shown great potential toward this goal due to their excellent optoelectronic properties. Continuous-wave (CW) optically pumped lasing in a real electroluminescent device represents a key step to current-injection laser diodes, but it has not yet been realized. This is mainly due to the challenge of incorporating a resonant cavity into an efficient light-emitting diode (LED) able to sustain intensive carrier injection. Here, CW lasing is reported in an efficient perovskite LED with an integrated distributed feedback resonator, which shows a low lasing threshold of 220 W cm-2 at 110 K. Importantly, the LED works well at a current density of 330 A cm-2 , indicating the carrier injection rate already exceeds the threshold of optically pumping. The results suggest that electrically pumped perovskite laser diodes can be achieved once the Joule heating issue is overcome.
RESUMO
The external quantum efficiency (EQE) of state-of-the-art planar-structure perovskite light-emitting diodes (PeLEDs) is mainly limited by the outcoupling efficiency, which is around 20% and decreases significantly with the perovskite thickness. Here, an approach to artificially form textured perovskite films to boost the outcoupling limit of the PeLEDs is reported. By manipulating the dwell time of antisolvents, the perovskite phase precipitation mechanism, film-forming process, and surface texture can be finely controlled. The film surface roughness can be tuned from 15.3 to 241 nm, with haze increasing accordingly from 6% to >90% for films with an average thickness of 1.5 µm. The light outcoupling limit increases accordingly from 11.7% for the flat PeLEDs to 26.5% for the textured PeLEDs due to photon scattering at the interface. Consequently, the EQE is boosted significantly from around 10% to 20.5% with an extraordinarily thick emissive layer of 1.5 µm. This study provides a novel way of forming light-extraction nanostructures for perovskite optoelectronic devices.
RESUMO
Light-emitting diodes (LEDs) based on perovskites show great potential in lighting and display applications. However, although perovskite films with high photoluminescence quantum efficiencies are commonly achieved, the efficiencies of perovskite LEDs are largely limited by the low light out-coupling efficiency. Here, we show that high-efficiency perovskite LEDs with a high external quantum efficiency of 20.2% and an ultrahigh radiant exitance up to 114.9 mW cm-2 can be achieved by employing the microcavity effect to enhance light extraction. The enhanced microcavity effect and light out-coupling efficiency are confirmed by the study of angle-dependent emission profiles. Our results show that both the optical and electrical properties of the device need to be optimized to achieve high-performance perovskite LEDs.
RESUMO
Perovskite light-emitting diodes (PeLEDs) have attracted considerable attention because of their potential in display and lighting applications. To promote commercialization of PeLEDs, it is important to improve the external quantum efficiency of the devices, which depends on their internal quantum efficiency (IQE) and light extraction efficiency. Optical simulations have revealed that 20-50% of the light generated in the device will be lost to surface plasmon (SP) modes formed in the metal/dielectric interfaces. Therefore, extracting the optical energy in SP modes to the air will greatly increase the light extraction efficiency of PeLEDs. In addition, the SPs can accelerate radiative recombination of the emitter via near-field effects. Thus, the IQE of a PeLED can also be enhanced by SP manipulation. In this review, first, general concepts of the SPs and how they can enhance the efficiency of LEDs are introduced. Then recent progresses in SP-enhanced emission of perovskite films and LEDs are systematically reviewed. After that, the challenges and opportunities of the SP-enhanced PeLEDs are shown, followed by an outlook of further development of the SPs in perovskite optoelectronic devices.
