Highly luminescent polyfluorene-based composite with CsPbX3 perovskite nanocrystals for light-emitting devices

The rapid development of thin-film light emitting devices (LED) technologies has recently been associated with the superior optoelectronic properties of luminescent materials based on lead halide perovskite nanocrystals (NCs) due to their narrow emission line with high color purity. However, the large surface area of NCs leads to the need to use solvating ligands to prevent their agglomeration, which limits their use in optoelectronics. Here we develop a class of modular polyfluorene (PF) copolymer with 4-hydroxyphenyl-, diethylamino- and diethoxyphosphoryl- groups designed to stabilize perovskite NCs. We show that as-synthesized CsPbBr₃ NCs can easily be mixed with custom-designed PFs resulting in polymer/NCs composite that shows efficient Förster energy transfer (FRET) from PF to NC with green photoluminescence (PL). We also found that the NCs composite studied here can be used as an effective emissive layer in LED due to the strong interaction between polymer host and perovskite NCs providing an efficient charge transfer from the PF matrice to the NC emitter. The fabricated LED show excellent performance with a highest current efficiency of ∼25.2 cd A^–1. Our approach provides a low-cost and efficient way for light-emitting optoelectronic applications based on perovskite NCs.