Self-Generated Buried Submicrocavities for High-Performance Near-Infrared Perovskite Light-Emitting Diode

e-ISSN 2150-5551 CN 31-2103/TB ARTICLE Cite as Nano-Micro Lett. (2023) 15:125 Received: 22 February 2023 Accepted: 19 April 2023 © The Author(s) 2023 https://doi.org/10.1007/s40820-023-01097-3 Self‑Generated Buried Submicrocavities for High‑Performance Near‑Infrared Perovskite Light‑Emitting Diode Jiong Li1, Chenghao Duan1,3, Qianpeng Zhang2, Chang Chen1, Qiaoyun Wen1, Minchao Qin3, Christopher C. S. Chan4, Shibing Zou1, Jianwu Wei5, Zuo Xiao6, Chuantian Zuo6, Xinhui Lu3, Kam Sing Wong4, Zhiyong Fan2 *, Keyou Yan1 * HIGHLIGHTS • Synergistic effect triggers the Ostwald ripening for the downward recrystallization of perovskite to form buried submicrocavities as light output coupler. • The simulation suggests the buried submicrocavities can improve the light out-coupling efficiency from 26.8% to 36.2% for nearinfrared light. • Light-emitting diodes yields peak external quantum efficiency increasing from 17.3% at current density of 114 mA cm−2 to 25.5% at current density of 109 mA cm−2 and a radiance increasing from 109 to 487 W sr−1 m−2 with low rolling-off. ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency (LOCE) for planar perovskite light-emitting diodes (PeLEDs). In this work, we employ phenethylammonium iodide (PEAI) to trigger the Ostwald ripening for the downward recrystallization of perovskite, resulting in spontaneous formation of buried submicrocavities as light output coupler. The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2% for near-infrared light. Therefore, PeLED yields peak external quantum efficiency (EQE) increasing from 17.3% at current density of 114 mA cm−2 to 25.5% at current density of 109 mA cm−2 and a radiance increasing from 109 to 487 W s r−1 m−2 with low rolling-off. The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr−1 m−2. Besides, downward recrystallization process slightly reduces the trap * Zhiyong Fan, ; Keyou Yan, 1 School of Environment and Energy, State Key Lab of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, South China University of Technology, Guangzhou 510000, People’s Republic of China 2 Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China 3 Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, People’s Republic of China 4 Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, People’s Republic of China 5 School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, People’s Republic of China 6 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing 100190, People’s Republic of China Vol.:(0123456789) 13 125 Page 2 of 13 Nano-Micro Lett. (2023) 15:125 density from 8.90 × 1015 to 7.27 × 1015 cm−3. This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs. KEYWORDS Perovskite light-emitting diodes; Downward recrystallization; Buried submicrocavities; Light out-coupling efficiency; Radiative recombination 1 Introduction With high photoluminescence quantum yield (PLQY), tunable emission wavelength and narrow full width at half maximum (FWHM), perovskite light-emitting diodes (PeLEDs) are regarded as the promising candidate for next-generation solid-state lightings and high-definition displays [1–5]. The external quantum efficiency (EQE) of PeLEDs is, however, restricted by factors such as the quality of the perovskite films, probability of balanced charge injection and light outcoupling efficiency (LOCE) [6–8]. At present, recrystallization has become one of the commonly used methods to reduce defects, suppress nonradiative recombination and optimize the quality of perovskite films, including post-processing, vapor-assisted annealing and flash-induced annealing [9–11]. In addition, the LOCE also plays a crucial role in the electroluminescence (EL) [12, 13]. Theoretical analysis shows that the LOCE of planar PeLEDs is ~ 20%, which is mainly due to the high refractive index of the perovskite layer, trapping most of the light inside [14–17]. Therefore, it is still meaningful to develop a simple optical output micro-nanostructure to effectively improve the LOCE and performance of PeLEDs. Herein, we adopted a simple route to post-treat perovskite film with phenethylammonium iodide (PEAI) and triggered downward recrystallization of perovskite, resulting in spontaneous formation of buried submicrocavities. The simulation result suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2% by coupling the waveguide modes to substrate modes. Besides, Ostwald ripening process slightly passivates the traps and thus reduces the nonradiative recombination losses as well. Therefore, PeLED yields peak EQE increasing from 17.3% at current density of 114 mA cm−2 to 25.5% at current density of 109 mA cm−2 and a radiance increasing from 109 to 487 W sr−1 m−2 with low rolling-off. The turn-on voltage at 0.1 W sr−1 m−2 is 1.15 V, lower than 1.25 V for the control. The statistical result indicates 95% of the devices with PEAI can achieve a peak EQE of more than 20%, with nice repeatability PeLED exhibits good spectral stability under different bias voltages © The authors and the T75 (T75, defined as the time taken for the EQE to drop to 75% of its initial value) exceeds 15 h. 2 Material and Methods 2.1 Materials The zinc oxide nanoparticles (ZnO NPs) were synthesized from potassium hydroxide (KOH, CAS no. 1310-58-3, Aladdin, 99.99%) and zinc acetate dihydrate (Zn(Ac)2.2H2O, CAS no. 5970-45-6, Macklin, 99.99%). 2,2′,7,7′-Tetrakis [N, N-di(4-methoxyphenyl) amino]-9,9′-spirobifluorene (SpiroOMeTAD, CAS no. 207739-72-8, 99.95%), Phenethylammonium iodide (PEAI, CAS no. 151059-43-7, ≥ 99.5%) and Lead iodide (PbI 2, CAS no. 10101-63-0, 99.99%) were purchased from Xi’an Polymer Light Technology Corp. N,N-Dimethylformamide (DMF, CAS no. 68-12-2, 99.5%), β-Alanine (CAS no. 107-95-9, 99%) and Molybdenum trioxide ( MoOx, CAS no. 1313-27-5, 99.95%) were purchased from Aldrich. Formamidinium iodide (FAI, CAS no. 879643-71-7, 99.5%) and the patterned ITO glass was purchased from Advanced Election Technology Co., Ltd. 2.2 Synthesis of ZnO NPs ZnO nanoparticles were synthesized by reacting KOH with Zn(Ac)2·2H2O in methanol for 2 h at 60 °C. After centrifuging and dispersing in methanol for three times, the precipitate is dispersed it in methanol and chloroform for using. 2.3 Device Fabrication To prepare a perovskite precursor solution with a concentration of 0.7 M, β-Alanine, FAI, PbI2 were dissolved in a molar ratio of (0, 0.1, 0.15, 0.2): 1.8: 1.0 in 1 mL of DMF and (...truncated)