Interfacial Potassium‐Guided Grain Growth for Efficient Deep‐Blue Perovskite Light‐Emitting Diodes

Abstract

Perovskite light‐emitting diodes (PeLEDs) are emerging candidates for the applications of solution‐processed full‐color displays. However, the device performance of deep‐blue PeLED still lags far behind that of their red and green counterparts, which is largely limited by low external quantum efficiency (EQE) and poor operational stability. Here, a facile and reliable crystallization strategy for perovskite grains is proposed, with improved deep‐blue emission through rational interfacial engineering. By modifying the substrate with potassium cation (K+) as the supplier of heterogeneous nucleation seeds, the interfacial K+‐guided grain growth is realized for well‐packed perovskite assemblies with high surface coverage and the controlled crystal orientation, leading to the enhanced radiative recombination and hole‐transport capabilities. Synergistical boost in device performance is achieved for deep‐blue PeLEDs emitting at 469 nm with a peak EQE of 4.14%, a maximum luminance of 451 cd m–2, and spectrally stable color coordinates of (0.125, 0.076) that matches well with the National Television System Committee (NTSC) standard blue.

Strategies Toward Efficient Blue Perovskite Light‐Emitting Diodes

“…Reproduced with permission. [ 101 ] Copyright 2020, Wiley‐VCH. d) Current–voltage ( J–V ) response of pristine and RbBr‐rich perovskite films in SCLC measurement.…”

“…As a result, the fabricated PeLEDs showed an improved EQE of 4.14% at 469 nm. [ 101 ] Yuan et al. reported a Rubidium–Cesium alloyed, quasi‐2D perovskite, in which they demonstrated excess RbBr could effectively passivate the perovskite defect states by affecting the crystallization process as well as crystal orientation.…”

Recent Advances in Multi‐Layer Light‐Emitting Heterostructure Transistors

“…[ 108,116 ] Especially for photovoltaics and LEDs, various strategies have been used to improve the efficiency and long‐term stability, which included defect passivation by ion doping in the ETL and active layer, [ 117–120 ] introduction of optimized electrodes, [ 121 ] and simplified device structure by optimizing carrier transport layers. [ 122,123 ] Based on these strategies, the performance of perovskite LED and photovoltaics gradually increased and even exceeded that of OLED and organic photovoltaics. On the other hand, LETs based on perovskites have only been reported recently and they are expected to become an emerging development direction of LETs with outstanding optoelectronic properties.…”

Strategies to Improve Luminescence Efficiency and Stability of Blue Perovskite Light‐Emitting Devices

“…To avoid the influence of the incorporated organic additives on the transport properties of perovskite films, Shen et al modified the substrate with potassium (K + ) cations to improve radiative recombination and hole‐transport capabilities, arising from strong dipole interaction between K + and halide ions. [ 60 ] The K + ‐triggered nucleation and grain growth promoted the formation of well‐packed (Cs/FA/p‐F‐PEA) Pb(Cl/Br) 3 perovskite film with a PLQY of 34.8%, and thereby a deep‐blue PeLEDs ( λ EL = 469 nm) was obtained with an EQE max of 4.14%. Yan et al synthesized a stable pure layered (benzimidazole) 2 PbBr 4 (BI 2 PbBr 4 ) perovskite via the strong π–π interaction between benzene rings of the BI ligand, leading to the 2D‐layered perovskite film with a PLQY of 80% and the deep‐blue PeLED ( λ EL = 445 nm) with an EQE max of 3.08% and a L max of 1315 cd m −2 .…”