Dual-Hole-Transport-Layer-Facilitated Efficient Perovskite Light-Emitting Diode

The improved luminescence and colour purity of solution-processable perovskite materials have positioned them as promising candidates for advanced lighting technologies. Herein, a simple method is presented for fabricating dual hole-transport layers (HTLs) of green perovskite light-emitting diodes (PeLEDs), for improved charge balance in the emissive layer (EML). With well-matched energy levels, and lowered charge injection barrier of the transport layers, maximum radiative recombination in the EML can be obtained. The varying highest occupied molecular orbital (HOMO) levels of the HTLs used in the device are in alignment with the work function of the fluorine-doped tin oxide and HOMO of the EML. The poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine (PEDOT:PSS/NPD)-based PeLED device shows outstanding performance with a maximum brightness of 19625 cd m⁻², highest current efficiency of 19.2 cd A⁻¹, and turn-on voltage of 3.8 V among the all HTL combinations. These improvements are attributed to the well-matched HOMO of NPD and PEDOT:PSS, with both the anode and EML allowing improved hole injection and charge balance. Electroluminescence supports the coordinates (0.22, 0.74) for pure green emission provided by the Commission Internationale de I’Eclairage. Perovskite films fabricated on top of PEDOT:PSS/NPD have the best film morphology and crystallinity with the fewest pinholes enabling improved charge transport.