Thermal evaporation offers a promising route toward scalable manufacturing and high-resolution pixel patterning of perovskite light-emitting diodes (PeLEDs). However, evaporated PeLEDs have long lagged behind their solution-processed counterparts in efficiency, largely due to rapid and poorly controlled crystallization during vacuum deposition.
In a recent study published in Nature Photonics, research teams led by Prof. Chunxiong Bao and Prof. Tao Yu at Nanjing University and Prof. Feng Gao at Linköping University systematically investigated the crystallization dynamics of evaporated perovskites using in situ optical spectroscopy and grazing-incidence wide-angle X-ray scattering (GIWAXS). These investigations revealed premature perovskite formation during deposition and distinct crystallization stages during annealing. Based on these insights, the researchers introduced a hydrogen-bond-network-mediated strategy using 2,6-pyridinedicarboxamide (PyDA) to suppress premature perovskite formation and regulate subsequent crystallization.
This strategy enabled thermally evaporated near-infrared PeLEDs with an external quantum efficiency (EQE) of 25.0%, approaching the performance of leading solution-processed devices. The team further demonstrated monolithically integrated dual-wavelength PeLED pixels emitting at 805 and 759 nm on a single substrate. These advances highlight the potential of crystallization engineering for efficient, scalable and pixelated PeLED technologies.
Figure (a) In situ monitoring setup used to reveal rapid crystallization and phase evolution in evaporated perovskites. (b) A PyDA-mediated hydrogen-bonding network suppresses premature perovskite formation and regulates crystallization during annealing. (c) The optimized near-infrared PeLED achieves a peak EQE of 25.0%. (d,e) Monolithic integration of dual-wavelength PeLED pixels emitting at 805 and 759 nm.
Publication: Y. Liu et al. Regulating the crystallization of thermally evaporated perovskites for efficient near-infrared light-emitting diodes. Nature Photonics (2026).
link: https://doi.org/10.1038/s41566-026-02036-5