Work-function tuneable and aqueous solution-processed Cs2CO3 for high-performance polymer solar cells

The authors demonstrate an aqueous solution-processed Cs2CO3 thin film with an adjustable work function via MoO3 and/or Na2WO4 doping. The doped Cs2CO3 as a cathode interfacial layer is successfully used in poly(3-hexyl-thiophene) (P3HT)/indene-C60 bisadduct (IC60BA) heterojunction based solar cells with improved open-circuit voltage and unaffected short-circuit current density. X-ray photoelectron spectroscopy (XPS) evaluation was conducted to verify the formation of the new composites of W–O–Cs and Mo–O–Cs after doping of MoO3 and/or Na2WO4 into Cs2CO3. The change of the work function of MoO3- and/or Na2WO4-doped Cs2CO3 was further confirmed by ultraviolet photoelectron spectroscopy (UPS) measurements.