African Journal of
Pure and Applied Chemistry

  • Abbreviation: Afr. J. Pure Appl. Chem.
  • Language: English
  • ISSN: 1996-0840
  • DOI: 10.5897/AJPAC
  • Start Year: 2007
  • Published Articles: 357

Full Length Research Paper

Efficiency enhancement in P3HT:PCBM blends using Squarylium III dye

M. Tembo1*, M. O. Munyati2, S. Hatwaambo1 and M. Maaza3
1Department of Physics, School of Natural Sciences, University of Zambia, P. O. Box 32379, Lusaka, 10101 Zambia. 2Department of Chemistry, School of Natural Sciences, University of Zambia, P. O. Box 32379, Lusaka, 10101 Zambia. 3Nanosciences Laboratories, Materials Research Department, iThemba LABS, P. O. Box 722, Somerset West 7129, Western Cape, South Africa.
Email: [email protected]

  •  Received: 24 September 2014
  •  Accepted: 27 January 2015
  •  Published: 31 March 2015

Abstract

Nano-size thin films comprising poly (3-hexylthiophene) (P3HT) and a fullerene derivative [6, 6] phenyl-C61-butyric acid methyl ester (PCBM) incorporating squarylium dye III (SQ3) are reported. The materials prepared were evaluated for their optical, electrical and photo-conversion efficiency. Active layer materials comprising a blend of P3HT:SQ3:PCBM were deposited by spin-coating to produce thin films measuring 100 nm and subsequently annealed at 140°C for 10 min. The films were characterized by UV-Vis-NIR spectroscopy for their optical properties, atomic force microscopy for surface morphology and film thickness, and electrical properties. Optical measurements for blends incorporating different amounts of dye showed increased photo-absorbance with increasing dye concentration. The combined contribution of SQ3 and thermal annealing resulted in increased power conversion efficiency (η) of pristine P3HT:PCBM solar cells from 1.9 to 3.9 %. The dye in the active layer improved photo-absorption by enhanced light harvesting while thermal treatment improved the nanoscale morphology leading to better metal-film interface contact and broadening of the absorption wavelength range.
 
Key words: Polymer solar cell (PSC), squarylium dye III (SQ3), bulk hetero-junction (BHJ), power conversion efficiency (PCE), poly (3-hexylthiophene (P3HT), [6, 6]-phenyl C60 butyric acid methyl ester (PCBM).

Abbreviation

BHJ, Bulk hetero-junction; HOMO, Highest occupied molecular orbital; LUMO, Lowest unoccupied molecular orbital; OPVs, Organic Photovoltaics; P3HT, poly (3-hexylthiophene); PCBM, [6, 6]-phenyl C60 butyric acid methyl ester; PCE, Power conversion efficiency; PEDOT:PSS, 3, 4-polyethylenedioxythiophene-polystyrenesulfonate; PSCs, Polymer Solar Cells; PV, Photovoltaic; QE, Quantum efficiency; SQ3, Squarylium III dye.