Minimising efficiency roll-off in high-brightness perovskite light-emitting diodes

Abstract

Efficiency roll-off is a major issue for most types of light-emitting diodes (LEDs), and its origins remain controversial. Here we present investigations of the efficiency roll-off in perovskite LEDs based on two-dimensional layered perovskites. By simultaneously measuring electroluminescence and photoluminescence on a working device, supported by transient photoluminescence decay measurements, we conclude that the efficiency roll-off in perovskite LEDs is mainly due to luminescence quenching which is likely caused by non-radiative Auger recombination. This detrimental effect can be suppressed by increasing the width of quantum wells, which can be easily realized in the layered perovskites by tuning the ratio of large and small organic cations in the precursor solution. This approach leads to the realization of a perovskite LED with a record external quantum efficiency of 12.7%, and the efficiency remains to be high, at approximately 10%, under a high current density of 500 mA cm −2 .

Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

“…The inorganic slabs serve as the potential wells while the organic layers function as the potential barriers. The band gap of each quantum‐well is mainly determined by the number of inorganic monolayer sheets within a layered perovskite . The MQW electronic structure enables 2D halide perovskite particularly interesting for optoelectronic applications and magnetic studies .…”

Highly Efficient Guanidinium‐Based Quasi 2D Perovskite Solar Cells via a Two‐Step Post‐Treatment Process

“…This ACI type perovskite can be described by the formula of GAMA n Pb n I 3 n +1 or (GAMA)MA n −1 Pb n I 3 n +1 (GA = guanidinium, MA = methylammonium), where two different kinds of cations (GA + and MA + ) are combined in the interlayer space. The ACI 2D perovskites exhibit narrower optical bandgaps, lower exciton binding energy, and longer carrier lifetime ascribed to the small volume of GA and MA, compared with typical RP 2D perovskites which have higher exciton binding energy and inefficient charge transfer due to the multiple quantum wells structure within the films …”

Control of Interface Defects for Efficient and Stable Quasi‐2D Perovskite Light‐Emitting Diodes Using Nickel Oxide Hole Injection Layer

“…Metal halide perovskites (MHPs) have emerged as a promising class of materials for optically pumped lasers and light‐emitting diodes (LEDs) owing to their narrow emission spectrum and wide range of color tunability 1, 2, 3, 4, 5, 6, 7. To date, perovskite LEDs (PeLEDs) have recorded an external quantum efficiency (EQE) of up to 14.36% for green emissions6 and 12.7% for near‐infrared emissions 7.…”

“…To date, perovskite LEDs (PeLEDs) have recorded an external quantum efficiency (EQE) of up to 14.36% for green emissions6 and 12.7% for near‐infrared emissions 7. However, the low exciton binding energy in MHPs is a fundamental limitation that leads to the generation of free charges at room temperature.…”