Perovskite light‐emitting diodes (PeLEDs) have recently shown significant progress with external quantum efficiencies (EQEs) exceeding 20%. However, PeLEDs with pure‐red (620−660 nm) light emission, ...an essential part for full‐color displays, remain a great challenge. Herein, a general approach of spacer cation alloying is employed in Ruddlesden–Popper perovskites (RPPs) for efficient red PeLEDs with precisely tunable wavelengths. By simply tuning the alloying ratio of dual spacer cations, the thickness distribution of quantum wells in the RPP films can be precisely modulated without deteriorating their charge‐transport ability and energy funneling processes. Consequently, efficient PeLEDs with tunable emissions between pure red (626 nm) and deep red (671 nm) are achieved with peak EQEs up to 11.5%, representing the highest values among RPP‐based pure‐red PeLEDs. This work opens a new route for color tuning, which will spur future developments of pure‐red or even pure‐blue PeLEDs with high performance.
A simple and general strategy of spacer cation alloying is developed to modulate the thickness distribution of quantum wells in Ruddlesden–Popper perovskite films. Based on this method, efficient perovskite light‐emitting diodes with tunable emissions between pure red (626 nm) and deep red (671 nm) are achieved with peak external quantum efficiencies up to 11.5%.
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.
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.
Ruddlesden–Popper perovskites (RPPs), consisting of alternating organic spacer layers and inorganic layers, have emerged as a promising alternative to 3D perovskites for both photovoltaic and ...light‐emitting applications. The organic spacer layers provide a wide range of new possibilities to tune the properties and even provide new functionalities for RPPs. However, the preparation of state‐of‐the‐art RPPs requires organic ammonium halides as the starting materials, which need to be ex situ synthesized. A novel approach to prepare high‐quality RPP films through in situ formation of organic spacer cations from amines is presented. Compared with control devices fabricated from organic ammonium halides, this new approach results in similar (and even better) device performance for both solar cells and light‐emitting diodes. High‐quality RPP films are fabricated based on different types of amines, demonstrating the universality of the approach. This approach not only represents a new pathway to fabricate efficient devices based on RPPs, but also provides an effective method to screen new organic spacers with further improved performance.
A novel method is developed for fabricating high‐quality Ruddlesden–Popper perovskite films by directly using commercially available organic amines, avoiding extra chemical synthesis processing of organic ammonium halides. This new approach results in similar (and even better) device performance for both solar cells and light‐emitting diodes when compared with control devices fabricated from organic ammonium halides.
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