Electronic structure, molecular orientation, charge transfer dynamics and solar cells performance in donor/acceptor copolymers and fullerene: Experimental and theoretical approaches

Journal Article · Mon Apr 07 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4870470· OSTI ID:22273705

Garcia-Basabe, Y.; Rocco, M. L. M., ^[1]; Marchiori, C. F. N.; Yamamoto, N. A. D.; Koehler, M.; Macedo, A. G. ^[2]

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1. Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro 21941-909 (Brazil)
2. Departament of Physics, Technological Federal University of Paraná, Curitiba 80230-901 (Brazil)

By combining experimental and theoretical approaches, the electronic structure, molecular orientation, charge transfer dynamics and solar cell performance in donor/acceptor copolymer poly[2,7-(9,9-bis(2-ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl) benzo-2,1,3-thiadiazole] (PSiF-DBT) films and blended with 6,6.-phenyl-C 61-butyric acid methyl ester (PSiF-DBT:PCBM) were investigated. Good agreement between experimental and theoretical PSiF-DBT UV-Vis absorption spectrum is observed and the main molecular orbitals contributing to the spectrum were determined using DFT single point calculations. Non-coplanar configuration was determined by geometric optimization calculation in isolated PSiF-DBT pentamer and corroborated by angular variation of the sulphur 1s near-edge X-ray absorption fine structure (NEXAFS) spectra. Edge-on and plane-on molecular orientations were obtained for thiophene and benzothiadiazole units, respectively. A power conversion efficiency up to 1.58%, open circuit voltage of 0.51 V, short circuit current of 8.71 mA/cm{sup 2} and a fill factor of 35% was obtained using blended PSiF-DBT:PCBM as active layer in a bulk heterojunction solar cell. Ultrafast electron dynamics in the low-femtosecond regime was evaluated by resonant Auger spectroscopy using the core-hole clock methodology around sulphur 1s absorption edge. Electron delocalization times for PSiF-DBT and PSiF-DBT:PCBM polymeric films were derived for selected excitation energies corresponding to the main transitions in the sulphur 1s NEXAFS spectra. The mixture of PSiF-DBT with PCBM improves the charge transfer process involving the π* molecular orbital of the thiophene units.

• OSTI ID: 22273705
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
BUTYRIC ACID
COPOLYMERS
ELECTRONIC STRUCTURE
ELECTRONS
ENERGY CONVERSION
ESTERS
FINE STRUCTURE
FULLERENES
HETEROJUNCTIONS
HOLES
MOLECULAR ORBITAL METHOD
POLYCYCLIC SULFUR HETEROCYCLES
SOLAR CELLS
SULFUR
SUPERCONDUCTING FILMS
THIOPHENE
X-RAY SPECTROSCOPY