Investigation of the light-soaking effect in organic solar cells using dielectric permittivity and electric modulus approaches

• Published in: Organic electronics Vol. 52; pp. 32 - 41
• Main Authors: Symonowicz, J., Morawski, M., Dusza, M., Peksa, P., Sieradzki, A., Granek, F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2018
• Subjects: Dielectric spectroscopy; Light-soaking; Organic solar cell; P3HT:PCBM bulk heterojunction; ZnO; Dielectric spectroscopy; ZnO; P3HT:PCBM bulk heterojunction; Organic solar cell; Light-soaking
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2017.09.048

We demonstrate the influence of a light-soaking treatment on current-voltage characteristics, external quantum efficiency and dielectric response of an encapsulated P3HT:PCBM bulk heterojunction inverted organic solar cell. Furthermore, we apply dielectric permittivity and electric modulus approaches to identify relaxation peaks observed in this device. We discuss previously reported explanations of the light-soaking effect on the basis of our experimental results, showing that the light-soaking effect originates from dipole formation at the ZnO/P3HT:PCBM interface. In addition, we find that metal oxide hole and electron selective layers prevent the P3HT:PCBM molecules' reorientations and, thus, enhance its thermal stability. This type of experimental observations are expected to provide new prospective on the fundamental aspect of elementary charge transfer modifications in organic solar cells. [Display omitted] •The mechanism of light-soaking effect is related to charge transport properties.•Three peaks are distinguished from dielectric response of P3HT:PCBM BHJ.•Light-soaking increases the number of dipoles at ZnO/P3HT:PCBM interface.•Electron and hole selective layers enhance thermal stability of P3HT:PCBM.