Strategies to Improve the Stability of Perovskite Light-Emitting Diodes: Progress and Perspective

Abstract

Perovskite light-emitting diodes (PeLEDs) featuring excellent electroluminescent (EL) characteristics and facile production have been emerging as promising candidates for next-generation high-definition displays. In recent years, tremendous advances have been achieved in the EL efficiency of PeLEDs. However, their poor operational stability impedes practical applications. Particularly, the severe spectral instability of pure-blue and pure-red PeLEDs lags far behind the requirements of commercial displays. In this Perspective, the critical factors related to device degradation are first summarized, including perovskite crystal defects, unbalanced charge injection, Auger recombination, and Joule heating. Then, the recent progress in improving the operational and spectral stabilities is reviewed in categories. Considering the present achievements, we provide potential research directions for further development of stable PeLEDs.

Intrinsic stability of perovskite materials and their operational stability in light-emitting diodes

“…Joule heating is inevitably present in inorganic, 91,92 organic 93 and organic-inorganic hybrid LEDs. 87,[94][95][96] Due to Joule heating, the elevated temperature further enhances the non-radiative recombination through extended defect recombination, charge leakage/imbalance, and Auger recombination, which is detrimental to the EQE. Lin et al 92 examined the maximum limits of EQE in bare LEDs theoretically and experimentally.…”

Highly Stable Perovskite Nanocrystals with Pure Red Emission for Displays

“…Moreover, multilayer MHPs are unfavorable emitters with a broad emission spectrum and low efficiency. 17 Small-sized CsPbI 3 quantum dots (QDs) are more susceptible to Ostwald ripening and deterioration of the phase transition. 18−22 It has been proven that CsPbI 3−x Br x NCs can be used to prepare PeLEDs with high color purity.…”

“…To fabricate pure red PeLEDs, significant efforts have been made to approach the pure red emission of metal halide perovskites (MHPs) by alloying halide components (bromide partially replaces iodide, i.e., CsPbI 3– x Br x NCs), engineering structural dimensionality, and quantum confining the size of iodide perovskite (CsPbI 3 quantum dots). , However, reduction of structural dimensionality results in wide dimensional distribution, strong electron–phonon interaction, and low conductivity. Moreover, multilayer MHPs are unfavorable emitters with a broad emission spectrum and low efficiency . Small-sized CsPbI 3 quantum dots (QDs) are more susceptible to Ostwald ripening and deterioration of the phase transition. − …”

Recent Advances and Perspectives of Metal Halide Perovskite Heteronanocrystals

“…4−6 However, the soft ionic nature and low formation energy of the perovskites lead to their labile surface and dynamic ligand capping, which induce rapid decomposition and halide ion segregation when the PNCs are exposed in a combination of light, heat, and moisture. 7,8 Fabrication of perovskite heteronanocrystals (PHNCs) by growing a semiconductor with more covalent characteristic on ionic PNCs provides enormous benefits, including minimized surface trap states, increased carrier transfer or exciton recombination, widened tuning range of optical and electrical properties, and significantly improved stability. 9,10 Over the past years this has spurred an intense research activity to grow PHNCs with metal salts, 11,12 metal chalcogenide, 13,14 and metal oxides.…”

“…Colloidal heteronanocrystals that combine different semiconductors together through a lattice matched heterointerface are widely known for their excellence in surface passivation and engineering optical and electrical properties, which have fueled significant progress for nanocrystals composed of II–VI, III–V, IV–VI, and I–III–V group semiconductors. − Lead halide perovskite nanocrystals (PNCs) have recently emerged as promising candidates for a broad range of applications in light conversion and harvesting because of their remarkable optical and electrical properties, such as high photoluminescent efficiency, high defect tolerance, and significant cost advantage over classical nanocrystals. − However, the soft ionic nature and low formation energy of the perovskites lead to their labile surface and dynamic ligand capping, which induce rapid decomposition and halide ion segregation when the PNCs are exposed in a combination of light, heat, and moisture. , Fabrication of perovskite heteronanocrystals (PHNCs) by growing a semiconductor with more covalent characteristic on ionic PNCs provides enormous benefits, including minimized surface trap states, increased carrier transfer or exciton recombination, widened tuning range of optical and electrical properties, and significantly improved stability. , Over the past years this has spurred an intense research activity to grow PHNCs with metal salts, , metal chalcogenide, , and metal oxides. , …”