AB Epoxy Encapsulation-Induced Transparency in Perovskite Films for Light-Emitting Diode Applications
Perovskite light-emitting diodes (PeLEDs) are a promising display technology due to high color purity and solution processability, but their operational stability is compromised by environmental degradation. Encapsulation is essential for practical deployment. Here, we report that applying a commercial AB epoxy adhesive as a cover encapsulant induces a striking transparency transition in Cs0.3MA0.7PbBr3 perovskite films, from yellow to optically clear. The effect is attributed to the alkaline hardener (component B, pH 9–10), which engages in Lewis acid-base coordination with Pb2+ and reacts with Br−, as evidenced by Fourier-transform infrared spectroscopy (redshift of C–O–C stretch from 1035.56 to 1018.05 cm−1, Δν ≈ 17.5 cm−1) and X-ray photoelectron spectroscopy (Pb 4f shift of 0.25 eV, Br 3d5/2 shift of 0.45 eV). This chemical interaction refines perovskite grains to tens of nanometers, shifting light scattering from Mie to Rayleigh regime and enhancing transmittance. Encapsulated devices achieve a maximum luminance of 12,643 cd/m2, a low operational current density, and an increased breakdown voltage of 27 V. The work establishes a framework for selecting encapsulation materials that impart transparency, enabling applications in transparent displays, smart windows, and augmented reality.