Over 100‐nm‐Thick MoOx Films with Superior Hole Collection and Transport Properties for Organic Solar Cells

Abstract Herein, a novel and effective method to prepare n‐doped MoO x films with highly improved conductivity is reported. The MoO x films are readily prepared by spin‐coating an aqueous solution containing ammonium molybdate tetrahydrate and vitamin C (VC). As confirmed by UV–vis absorption, X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements, Mo(VI) is partially reduced to Mo(V) by VC, resulting in the n‐doping of MoO x . The conductivity of the n‐doped MoO x (H:V‐Mo) film can be enhanced by four orders of magnitude compared to pristine MoO x (H‐Mo), that is, from 1.2 × 10 −7 to 1.1 × 10 −3 S m −1 . The device using a 10 nm H:V‐Mo anode interlayer (AIL) exhibits comparable photovoltaic performance to a poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)‐modified device. More importantly, the hole transport and collection properties of the H:V‐Mo AILs show outstanding tolerance to thickness variation, that is, with increasing thickness of the H:V‐Mo AIL from 10 to 150 nm, the V oc and fill factor values of the devices remain unchanged. The device based on the blade‐coated H:V‐Mo AIL also has a high power conversion efficiency of 10.6%. To the best of the authors' knowledge, this work demonstrates the first example to prepare metal oxide AILs with outstanding tolerance to thickness, which is promising for the future large‐area manufacturing.