title: Finding the lost open-circuit voltage in polymer solar cells by UV-ozone treatment of the nickel acetate anode buffer layer.
abstract: Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.
authors.affiliation: State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, Beijing Key Laboratory of Energy Security and Clean Utilization, North China Electric Power University , Beijing 102206, China.
authors.forename: Fuzhi
authors.initials: F
authors.lastname: Wang
authors.forename: Gang
authors.initials: G
authors.lastname: Sun
authors.forename: Cong
authors.initials: C
authors.lastname: Li
authors.forename: Jiyan
authors.initials: J
authors.lastname: Liu
authors.forename: Siqian
authors.initials: S
authors.lastname: Hu
authors.forename: Hua
authors.initials: H
authors.lastname: Zheng
authors.forename: Zhan'ao
authors.initials: Z
authors.lastname: Tan
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Li