Key Takeaways & Executive Findings
- •• • AB epoxy encapsulation induces transparency in Cs0.3MA0.7PbBr3 films via Lewis acid-base coordination, with FTIR redshift of C–O–C stretch from 1035.56 to 1018.05 cm−1 (Δν ≈ 17.5 cm−1), confirming Pb2+–ether interaction. • • XPS analysis reveals Pb 4f binding energy shift of 0.25 eV and Br 3d5/2 shift of 0.45 eV, indicating electron donation and partial Br consumption, which modifies the perovskite electronic environment. • • Grain refinement to tens of nanometers triggers a Mie-to-Rayleigh scattering transition, enhancing optical transmittance while maintaining green emission. • • Encapsulated PeLEDs achieve a maximum luminance of 12,643 cd/m2 and a breakdown voltage of 27 V, demonstrating improved operational stability without compromising brightness.
Abstract
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.
1. Introduction
Perovskite light-emitting diodes (PeLEDs) have emerged as a leading candidate for next-generation displays, offering high color purity and broad color gamut. However, their commercial viability is severely hampered by intrinsic instability: organic-inorganic perovskite films are susceptible to hydrolysis of Pb–Br bonds and oxidation of organic cations, leading to rapid performance decay. Encapsulation is therefore indispensable for protecting devices from environmental degradation. While cover encapsulation using epoxy resins is widely adopted, the chemical interactions between encapsulants and perovskite layers remain poorly understood, often resulting in unintended optical or electrical alterations.
This study addresses the critical bottleneck of encapsulation-induced degradation by systematically investigating the effect of a commercial AB epoxy adhesive on perovskite film properties. We discover that the hardener component (B) triggers a Lewis acid-base reaction with Pb2+ and Br−, causing a dramatic transparency transition. This phenomenon not only preserves device functionality but also enhances light outcoupling through grain refinement and scattering modulation. Our findings provide a rational framework for selecting encapsulation materials that can actively improve device performance, paving the way for robust, transparent PeLEDs suitable for flexible displays and smart optical devices.
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Jiamei Chen, Liang Chu (2026). AB Epoxy Encapsulation-Induced Transparency in Perovskite Films for Light-Emitting Diode Applications. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3552-2
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Frequently Asked Questions
What is the underlying chemical mechanism for the transparency transition in perovskite films upon AB epoxy encapsulation?
The transparency transition is driven by the alkaline hardener (component B, pH 9–10) which acts as a Lewis base. It coordinates with Pb2+ (Lewis acid) via ether linkages, as evidenced by FTIR redshift (Δν ≈ 17.5 cm−1) and XPS shifts (Pb 4f shift of 0.25 eV). Additionally, B reacts with Br−, leading to partial consumption of bromide ions (Br 3d5/2 shift of 0.45 eV). This chemical interaction induces lattice reconstruction and grain refinement to nanoscale, shifting scattering from Mie to Rayleigh regime, thereby enhancing transmittance.
How does the encapsulation affect the electrical performance and stability of PeLEDs?
Encapsulated devices exhibit a maximum luminance of 12,643 cd/m2, which is comparable to or better than unencapsulated devices, while operating at a low current density. The breakdown voltage is significantly enhanced to 27 V, indicating improved resistance to electrical stress. The encapsulation also protects against environmental degradation, extending operational lifetime.
Is the transparency effect specific to Cs0.3MA0.7PbBr3 or does it apply to other halide perovskites?
The effect is not limited to the Cs0.3MA0.7PbBr3 composition. The study demonstrates that component B also induces transparency in FAPbI3 (a red-emitting perovskite) and Cs2AgBiBr6 (a lead-free double perovskite), suggesting a general phenomenon applicable to various halide perovskites.
What are the implications of this work for the development of transparent display technologies?
The ability to render perovskite films transparent while maintaining green emission opens avenues for transparent luminescent films. This could enable see-through displays, smart windows, and augmented reality glasses where both transparency and light emission are required. The encapsulation method also provides a route to stabilize perovskite devices, addressing a key barrier to commercialization.
What are the potential scalability and cost considerations for industrial adoption?
AB epoxy adhesives are commercially available and cost-effective, making the encapsulation process scalable. The method is compatible with standard cover encapsulation techniques used in device fabrication. However, further optimization is needed to control the reaction kinetics and ensure uniform transparency across large areas. The study does not provide detailed cost analysis, but the use of low-cost materials suggests economic viability.
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