BPBiPA is anisotropic electron transporting layer (ETL) material with high electron mobility of 8.4 × 10−4 cm2 V−1 s−1 in the solid state. Developed for perovskite light-emitting diodes (PeLEDs) to enhance light outcoupling efficiency, BPBiPA has an anthracene core with 2-phenyl-1H-benzo[d]imidazole attached on each end, bridged by two phenyl linkers. The 2-phenyl-1H-benzo[d]imidazole end groups can help to reduce the trap state at the interface of ETL and emitting layer due to their strong nucleophilic property.
The anisotropic molecular orientations of BPBiPA gives a low refractive index which effectively enhances the photon extraction efficiency in waveguide mode thereby improves the light outcoupling efficiency of PeLEDs. Also, with high electron mobility, BPBiPA can facilitate balanced carrier injection in PeLEDs. Green PeLEDs with BPBiPA ETL shows a record high external quantum efficiency of 32.1% and a current efficiency of 111.7 cd A−1.