Weakly Confined Perovskite Nanocrystal Films for Energy-Efficient Electroluminescence Devices

Abstract High wall-plug efficiency (WPE) and long-term operational stability are major hurdles for perovskite light-emitting diodes (PeLEDs) toward low-power practical applications. This work presents high-WPE PeLEDs utilizing in situ fabricated weakly confined perovskite nanocrystal films with boosted stability. Reducing the proportion of bulky organic cations increases the nanocrystal size, causing a red-shift of the emission peak. A small-molecule salt is further introduced to regulate crystallization, reducing surface trap-state density and electron–phonon coupling strength. The resulting weakly confined nanocrystal films retain high WPE and an ultranarrow emission line width, while showing markedly better thermal and structural stability. Optimized device achieves a low turn-on voltage of 1.8 V, a peak WPE of 28.7%, and an ultranarrow electroluminescence line width of 17.6 nm. Notably, the device exhibited a T50 operational lifetime exceeding 10,000 h at 100 cd m–2. This study proves weakly confined perovskite nanocrystal engineering can synergistically enhance efficiency, stability, brightness and color purity, providing a feasible route to high-performance PeLEDs.