Van der Waals effects on structure and optical properties in organic photovoltaics. Issue 14 (3rd January 2019)

• Record Type: Journal Article
• Authors: Götz, Andreas W.; Rodríguez, Juan I.; Castillo‐Alvarado, Fray L.; Trujillo‐González, Daniel E.
• Is Part Of: International journal of quantum chemistry. Volume 119:Issue 14(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-01-03
• Subjects: OPV -- P3HT‐PCBM -- TDDFT -- UV‐Vis -- van der Waals; Quantum chemistry -- Periodicals; 541.28
• DOI: 10.1002/qua.25883
• Languages: English
• ISSNs: 0020-7608

Abstract

Abstract: We have recently reported that dispersion forces can have drastic effects on the structure and charge separation in organic photovoltaics (OPVs) (Martinez et al., J. Phys. Chem. C 121, 20 134 [2017]). Here we investigate dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. We show how van der Waals (vdW) interactions affect the geometrical structure, which has strong effects on the electronic structure and UV‐Vis absorption spectrum. Time‐dependent density functional theory calculations demonstrate that the experimentally observed blue‐shift of the absorption maximum of P3HT/PCBM OPV cells with respect to pure P3HT results mainly from distortions in P3HT due to vdW interactions between donor and acceptor fragments. Reduced absorption in the red region of the UV‐Vis spectrum results from distortions of P3HT and small charge transfer between P3HT and PCBM. These results are in qualitative agreement with experiments and recent theoretical results on the corresponding solid‐state films. Abstract : TDDFT calculations explain the experimentally observed blue‐shift of the absorption maximum in the active layer of P3HT/PCBM organic photovoltaic cells with respect to the absorption of pure P3HT. This effect is mainly due to distortions in the P3HT oligomer resulting from van der Waals interactions between donor and acceptor molecules. The reduced absorption intensity in the red region of the UV‐Vis spectrum results from distortions of P3HT and small charge transfer between P3HT and PCBM.