Sub-nanometer atomic layer deposited Al2O3 barrier layer for improving stability of nonfullerene organic solar cells

Abstract Organic solar cells (OSCs) is a promising next-generation photovoltaic technology, however, the device stability remains to be the main barrier for its future commercialization. Herein, we reported the application of a sub-nanometer Al2O3 barrier layer in nonfullerene OSCs via atomic layer deposition (ALD), for the purpose of preventing metal ion diffusion from indium tin oxide (ITO) into the polymer layer caused by the corrosion of Poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). The thickness of the ALD-Al2O3 barrier layer was precisely optimized by controlling the number of ALD cycles (n) to achieve simultaneously good photoelectric properties and conformal coverage. An average power conversion efficiency (PCE) of 15.02% was demonstrated for the optimal OSCs with ALD-Al2O3 barrier layer. The above mentioned suppression of metal ion diffusion was experimentally confirmed by the cross sectional observations of transmission electron microscopy (TEM) and chemical mapping from energy-dispersive X-ray spectroscopy (EDX), resulting in a significantly improved operational stability with a device lifetime 3-times longer than that without ALD-Al2O3 barrier layer. Such ALD-assisted interface modification provides an effective approach to realize high-performance and stable OSCs.