title: Comparative degradation and regeneration of polymer solar cells with different cathodes.
abstract: A comparative degradation study of solar cells based on a bulk-heterojunction (BHJ) blend of poly(3-hexylethiophene) (P3HT) and phenyl [6,6] C61 butyric acid methyl ester (PCBM) with two different cathodes is reported. Poly(ethylene-dioxythiphene):poly(styrene sulfonate) (PEDOT:PSS) coated ITO electrodes were used as the anode, whereas Ca/Al and Ca/Ag electrodes were used as cathodes. Fully degraded devices were subjected to thermal annealing under inert atmosphere. The performance of degraded solar cells with a Ca/Al cathode exhibited no improvement after treatment. However the solar cells with a Ca/Ag cathode exhibited a considerable recovery in their performance following annealing under a nitrogen atmosphere. Indeed, these solar cells could be subjected to many degradation and regeneration cycles. Current density-voltage (J-V) characteristics and X-ray photoelectron spectroscopy (XPS) studies show that this behavior arises from the complex chemical thermodynamics of the reactions that can occur at the cathode/active layer interface. In particular, the recovery of device performance for solar cells with a Ca/Ag cathode is due to the reversible oxidation of Ag upon thermal annealing.
authors.affiliation: CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Kumar
authors.forename: Chhinder
authors.initials: C
authors.lastname: Bilen
authors.forename: Krishna
authors.initials: K
authors.lastname: Feron
authors.forename: Nicolas C
authors.initials: NC
authors.lastname: Nicolaidis
authors.forename: Bill B
authors.initials: BB
authors.lastname: Gong
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Zhou
authors.forename: Warwick J
authors.initials: WJ
authors.lastname: Belcher
authors.forename: Paul C
authors.initials: PC
authors.lastname: Dastoor