Enhancing Light Outcoupling Efficiency via Anisotropic Low Refractive Index Electron Transporting Materials for Efficient Perovskite Light‐Emitting Diodes

Abstract

Thanks to the extensive efforts toward optimizing perovskite crystallization properties, high‐quality perovskite films with near‐unity photoluminescence quantum yield have been successfully achieved. However, the light outcoupling efficiency of perovskite light‐emitting diodes (PeLEDs) is impeded by insufficient light extraction, which poses a challenge to the further advancement of PeLEDs. Here, an anisotropic multifunctional electron transporting material, 9,10‐bis(4‐(2‐phenyl‐1H‐benzo[d]imidazole‐1‐yl)phenyl) anthracene (BPBiPA), with a low extraordinary refractive index (ne) and high electron mobility is developed for fabricating high‐efficiency PeLEDs. The anisotropic molecular orientations of BPBiPA can result in a low ne of 1.59 along the z‐axis direction. Optical simulations show that the low ne of BPBiPA can effectively mitigate the surface plasmon polariton loss and enhance the photon extraction efficiency in waveguide mode, thereby improving the light outcoupling efficiency of PeLEDs. Additionally, the high electron mobility of BPBiPA can facilitate balanced carrier injection in PeLEDs. As a result, high‐efficiency green PeLEDs with a record external quantum efficiency of 32.1% and a current efficiency of 111.7 cd A−1 are obtained, which provides new inspirations for the design of electron transporting materials for high‐performance PeLEDs.This article is protected by copyright. All rights reserved

Surface co-modification enabling efficient and spectrally stable mixed-halide blue light-emitting diodes

“…1 Since the advent of the first perovskite light-emitting diodes (PeLEDs) in 2014, 2 the external quantum efficiency (EQE) has been dramatically improved, with green and red PeLEDs exceeding the 25% milestone. 3–5 However, the color-stable and efficient blue PeLEDs are still far behind, especially for the blue emission with a wavelength less than 480 nm, which greatly limits their commercialization. 6–10…”

Eliminating Surface Plasmon Polariton Modes in Thin Film Light-Emitting Diodes through Planar Metamaterials

“…In the bottom-emission devices, thickening the transport layer between the metal mirror and active layer emerges as a more direct and effective scheme. However, it could raise the contact resistance of devices and intensify the light trapping as waveguide modes. − In particular, a few electron transport materials in organic light-emitting diodes (OLEDs) and perovskite LEDs possessing a low refractive index or negative birefringence have shown the feasibility of converting these SPP modes from surface waves to radiation, addressing the aforementioned issue. − Nonetheless, it remains a challenge to possess the necessary optical refractive index and high carrier mobility simultaneously.…”

Inorganic Cu2ZnSnS4 hole transport layer for perovskite light-emitting diodes

“…11 A few inorganic HTL materials have been incorporated into PeLEDs, including Cs 0.32 WO 3 , CuSCN, NiO x and Ni 0.9 Mg 0.1 O x , which afford comparable luminance and EQE. 12–16 However, there is still a shortage of P-type inorganic hole transport materials with both high mobility and deep HOMO energy levels to effectively match those mainstream electron transport layers with high electron mobility. Fortunately, the inorganic P-type semiconductor material Cu 2 ZnSnS 4 (CZTS), commonly known as a light absorber material, shows great potential to act as a promising HTL material for its high hole mobility (0–30 cm 2 V −1 s −1 ) and deep HOMO energy level (−5.57 eV).…”