Solution processable tungsten polyoxometalate as highly effective cathode interlayer for improved efficiency and stability polymer solar cells

Palilis, Leonidas C., Vasilopoulou, Maria, Douvas, Antonios M., Georgiadou, Dimitra G., Kennou, Stella, Stathopoulos, Nikolaos A., Constantoudis, Vassilios and Argitis, Panagiotis (2013) Solution processable tungsten polyoxometalate as highly effective cathode interlayer for improved efficiency and stability polymer solar cells. Solar Energy Materials and Solar Cells, 114, 205-213. (doi:10.1016/j.solmat.2013.02.034).

Abstract

We report for the first time the use of a water-soluble, tungsten polyoxometalate H₃PW₁₂O₄₀ (PW12-POM) as an efficient cathode interlayer incorporated into poly(3-hexylthiophene):[6,6]- phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM-61) polymer solar cells. The short circuit photocurrent density of the PW12-POM modified device is enhanced by ∼40% the open circuit voltage increases from 0.61 V to 0.65 V and the fill factor from 0.36 to 0.41, resulting to a power conversion efficiency enhancement of ∼70% (from 1.57% for the reference to 2.7% for the PW12-POM modified device). The improvement is attributed to enhanced electron transfer/extraction at the PW12-POM/Al interface as a result of the favorable interfacial energy level alignment and possible enhancement of the local electric field due to the nanoscale morphology of the PW12-POM layer, as evidenced by AFM measurements. A reduced degradation rate was measured for PW12-POM modified devices stored in dark and measured in ambient conditions. Taking into account the advantageous solution processability of PW12-POM, the large increase in the device efficiency and the improvement of their stability, we manifest that PW12-POM has highly desirable properties in order to be embedded as cathode interlayer in organic photovoltaic cells.

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Contributors

Author: Dimitra G. Georgiadou

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