Improved efficiency and stability of organic solar cells by interface modification using atomic layer deposition of ultrathin aluminum oxide

The interfacial contacts between the electron transporting layers (ETLs) and the photoactive layers are crucial to device performance and stability for OSCs with inverted architecture. Herein, atomic layer deposition (ALD) fabricated ultrathin Al₂O₃ layers are applied to modify the ETLs/active blends (PM6:BTP-BO-4F) interfaces of OSCs, thus improving device performance. The ALD-Al₂O₃ thin layers on ZnO significantly improved its surface morphology, which led to the decreased work function of ZnO and reduced recombination losses in devices. The simultaneous increase in open-circuit voltage ((Formula presented.)), short-circuit current density ((Formula presented.)) and fill factor (FF) were achieved for the OSCs incorporated with ALD-Al₂O₃ interlayers of a certain thickness, which produced a maximum PCE of 16.61%. Moreover, the ALD-Al₂O₃ interlayers had significantly enhanced device stability by suppressing degradation of the photoactive layers induced by the photocatalytic activity of ZnO and passivating surface defects of ZnO that may play the role of active sites for the adsorption of oxygen and moisture.