No abstract

We report a facile solution-based approach to the in situ growth of perovskite films consisting of monolayers of CsPbBr nanoplates passivated by bulky phenylbutylammonium (PBA) cations, that is, two-dimensional layered PBA(CsPbBr)PbBr perovskites. Optimizing film formation processes leads to layered perovskites with controlled n values in the range of 12-16. The layered perovskite emitters show quantum-confined band gap energies with a narrow distribution, suggesting the formation of thickness-controlled quantum-well (TCQW) structures. The TCQW CsPbBr films exhibit smooth surface features, narrow emission line widths, low trap densities, and high room-temperature photoluminance quantum yields, resulting in high-color-purity green light-emitting diodes (LEDs) with remarkably high external quantum efficiencies (EQEs) of up to 10.4%. The solution-based approach is extended to the preparation of TCQW CsPbI films for high-color-purity red perovskite LEDs with high EQEs of up to 7.3%.

Inorganic−organic hybrid perovskites have drawn considerable attention in photovoltaics and light-emitting diodes (LEDs) due to their exceptional optoelectronic properties. Perovskite multiple quantum wells (MQWs), which employ large organic ammonium cations to form layered structures, have been developed for high-efficiency perovksite LEDs (PeLEDs). However, little is known about the impacts of large organic ammonium cations on the properties of MQW films. In this work, we report MQW perovskites of phenylbutylammonium-cesium lead iodides, which exhibit a photoluminescence peak at 664 nm with a quantum efficiency of 58%. These perovskite MQW films enable red LEDs with high external quantum efficiencies (EQEs) of up to 13.3%. Furthermore, we deposit MQW perovskites of butylammonium-cesium lead iodides. The comparisons of the two perovskite MQW films demonstrate that the choices of large organic ammonium cations significantly influence the properties of the perovskite MQW films, that is, distributions of the quantum-well thicknesses, energy transfer processes, and recombination channels of the emissive centers. Our study shall shed light on the rational design of highperformance perovskite MQW films toward their potential application as red light sources.