High performance and stable all-inorganic perovskite light emitting diodes by reducing luminescence quenching at PEDOT:PSS/Perovskites interface

Compared to organic-inorganic halide perovskites (e.g., MAPbBr(3) and FAPbBr(3)), all-inorganic CsPbBr3 perovskite has shown to be a more promising candidate for application in light-emitting diodes (LEDs) due to higher photoluminescence quantum efficiency and thermal stability. Yet, the external quantum efficiency (EQE) of polycrystalline (3D) CsPbBr3 based PeLEDs needs further improvement. The low efficiency was attributed to severe luminescence quenching at PEDOT:PSS (Poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate))/ CsPbBr3 interface arising from (i) interfacial energy barrier between PEDOT:PSS and CsPbBr3 layer, (ii) poor crystallization and large pinholes in perovskite film, and (iii) indium fin oxide (ITO) anode etching due to PEDOT:PSS acidity. Therefore, it is necessary to address all these problems simultaneously to reduce the luminescence quenching and to improve device efficiency. Here, we introduce a feasible approach to modify the PEDOT:PSS layer in order to reduce the luminescence quenching at PEDOT:PSS/CsPbBr3 interface. In this modification, PEDOT:PSS is mixed with a MoO3 ammonia solution at desired volume ratios. Our studies demonstrate that upon this treatment, not only hole injection and crystallization of perovskite film are improved but also ITO is protected from etching by the acidic nature of PEDOT:PSS. This modification result in a high performance all inorganic CsPbBr3 LED with a maximum luminance of similar to 34420 cd/m(2) and a current efficiency of similar to 7.30 cd/A. In addition, our state-of-the-art perovskite LEDs (PeLEDs) exhibit no degradation after 2 h of continuous operation, representing a stable PeLEDs based on one-step solution processed polycrystalline CsPbBr3.