Stable and Pure-Red Perovskite Emission in Polymer-Perovskite Blend Enabled by FRET

Metal halide perovskites have emerged as one of the most promising semiconducting materials in the field of optoelectronics, especially for light-emitting diodes (LEDs), owing to their outstanding properties, such as high photoluminescence quantum yield (PLQY), exceptional color purity with narrow full-width-at-half-maximum (FWHM), wide color gamut, low manufacturing costs, and the ability to tune their emission spectrum. Pure-red emission (620–650 nm) is essential to comply with the Rec. 2020 standard for full-color displays, and is one of the three primary colors for displays. Although metal halide perovskites have demonstrated success in green and near-infrared emissions, achieving pure-red emission in perovskite-based display applications remains challenging due to persistent spectral instability. Although significant progress has been made using red-emitting quasi-2D perovskites, quantum dots, and mixed-halide perovskites, their performance under operational conditions often remains limited.
We address these challenges by embedding mixed-halide perovskite nanocrystals (PeNCs) into a polymer matrix to create a donor-acceptor architecture. In this work, methylammonium-based lead mixed-halide PeNCs serve as the emissive material (acceptor/guest). The hole-transporting polymer, poly (9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB), and the hole-transporting molecule 4,4'-bis (N-carbazolyl)-1,1'-biphenyl (CBP), together serve as the donor/host in the donor-acceptor system. The ternary blend of PeNCs, TFB, and CBP facilitate both cascade energy and charge transfer. All three components exhibit good miscibility, and the significant spectral overlap between the emission spectrum of the donor (TFB) and the absorption spectrum of the acceptor (PeNCs) enables efficient nonradiative energy transfer from TFB to PeNCs when excited at the absorption peak wavelength of TFB, indicating cascade energy transfer. The inclusion of CBP can enhance the charge-transfer efficiency and reduce exciton quenching, making the energy-transfer process more efficient. This hybrid system stabilizes the nanocrystals and enables efficient energy transfer via Förster resonance energy transfer (FRET) from donor to acceptor.
We observe enhanced acceptor photoluminescence and reduced donor lifetimes, confirming the effective FRET-mediated energy transfer. With a FRET rate of 0.18 ps^-1 and a FRET efficiency of 88.9%, our approach provides spectrally stable, pure-red emission. Moreover, it demonstrates a pathway for designing customized energy cascades, paving the way for next-generation optoelectronic devices with improved stability and performance.