CsPbBr₃ Perovskite Quantum Dot Light-Emitting Diodes Using Atomic Layer Deposited Al₂O₃ and ZnO Interlayers

Most CsPbBr₃ perovskite quantum dot light-emitting diodes (PQD-LEDs) are fabricated with an inverted device structure where hole transport/injection layers are vacuum-deposited on top of ITO/ZnO (as an electron transport layer (ETL))/PQDs. Standard device architecture of PQD-LEDs enables a solution-process of device fabrication; however, the spin-coating of ZnO ETL dissolved in polar solvent results in decreasing photoluminescence (PL) of PQDs because of PQD destabilization in polar medium. Herein, CsPbBr₃ PQD-LEDs are fabricated by depositing Al₂O₃ and ZnO via atomic layer deposition (ALD) to avoid damages originating from the polar solvent during ZnO ETL spin-coating. Low temperature ALD is adopted to prevent the coarsening of the CsPbBr₃ PQDs. A thicker Al₂O₃ interlayer can prevent PL quenching, but an excessively thick interlayer hinders electron transport due to the insulating nature of Al₂O₃. ZnO is sequentially deposited on Al₂O₃ interlayer via ALD, and therefore Al₂O₃/ZnO bilayer structure is used because of its better electron transporting ability and higher power efficiency in PQD-LED devices compared with Al₂O₃-only devices.