High‐efficiency, thermally activated delayed‐fluorescence organic light‐emitting diodes based on exciplex emitters are demonstrated. The best device, based on a TAPC:DPTPCz emitter, shows a high ...external quantum efficiency of 15.4%. Strategies for predicting and designing efficient exciplex emitters are also provided. This approach allow prediction and design of efficient exciplex emitters for achieving high‐efficiency organic light‐emitting diodes, for future use in displays and lighting applications.
Recently, Ruddlesden–Popper perovskites (RPPs) have attracted increasing interests due to their promising stability. However, the efficiency of solar cells based on RPPs is much lower than that based ...on 3D perovskites, mainly attributed to their poor charge transport. Herein, a simple yet universal method for controlling the quality of RPP films by a synergistic effect of two additives in the precursor solution is presented. RPP films achieved by this method show (a) high quality with uniform morphology, enhanced crystallinity, and reduced density of sub‐bandgap states, (b) vertically oriented perovskite frameworks that facilitate efficient charge transport, and (c) type‐II band alignment that favors self‐driven charge separation. Consequently, a hysteresis‐free RPP solar cell with a power conversion efficiency exceeding 12%, which is much higher than that of the control device (1.5%), is achieved. The findings will spur new developments in the fabrication of high‐quality, aligned, and graded RPP films essential for realizing efficient and stable perovskite solar cells.
A simple and universal method involving the use of two synergistic additives (dimethylsulfoxide and methylammonium chloride) into precursor solution is reported for growing high‐quality Ruddlesden–Popper perovskite films. Based on this method, hysteresis‐free solar cells with power conversion efficiencies over 12% and excellent reproducibility are achieved.
Nearly 100% triplet harvesting in conventional fluorophor‐based organic light‐emitting devices is realized through energy transfer from exciplex. The best C545T‐doped device using the exciplex host ...exhibits a maximum current efficiency of 44.0 cd A‐1, a maximum power efficiency of 46.1 lm W‐1, and a maximum external quantum efficiency of 14.5%.
A high‐performance hybrid white organic light‐emitting device (WOLED) is demonstrated based on an efficient novel thermally activated delayed fluorescence (TADF) blue exciplex system. This device ...shows a low turn‐on voltage of 2.5 V and maximum forward‐viewing external quantum efficiency of 25.5%, which opens a new avenue for achieving high‐performance hybrid WOLEDs with simple structures.
Although perovskite light-emitting diodes (PeLEDs) have recently experienced significant progress, there are only scattered reports of PeLEDs with both high efficiency and long operational stability, ...calling for additional strategies to address this challenge. Here, we develop perovskite-molecule composite thin films for efficient and stable PeLEDs. The perovskite-molecule composite thin films consist of in-situ formed high-quality perovskite nanocrystals embedded in the electron-transport molecular matrix, which controls nucleation process of perovskites, leading to PeLEDs with a peak external quantum efficiency of 17.3% and half-lifetime of approximately 100 h. In addition, we find that the device degradation mechanism at high driving voltages is different from that at low driving voltages. This work provides an effective strategy and deep understanding for achieving efficient and stable PeLEDs from both material and device perspectives.
Despite quick development of perovskite light‐emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain ...unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge–carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI3, resulting in more significant hysteresis and shorter operational stability of the PeLEDs.
It is found that the dynamic redistribution of mobile ions modifies the injection and transport property of charge carriers in the emissive layer, which can well explain the hysteresis in external quantum efficiency (EQE)– and radiance–voltage curves, as well as the rise phenomena of EQE and radiance under low constant driving voltages.
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