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

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 PCBMmore » improves the charge transfer process involving the π* molecular orbital of the thiophene units.« less
Authors:
; ;  [1] ; ; ; ;  [2] ;  [3]
  1. Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro 21941-909 (Brazil)
  2. Departament of Physics, Federal University of Paraná, Curitiba 81531-990 (Brazil)
  3. Departament of Physics, Technological Federal University of Paraná, Curitiba 80230-901 (Brazil)
Publication Date:
OSTI Identifier:
22273705
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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