Layered semiconductor tungsten disulfide: photoactive material in bulk heterojunction solar cells

We demonstrate 2D-layered semiconductor tungsten disulfide (WS2) nanoflakes as an efficient photoactive material in bulk heterojunction (BHJ) solar cells. WS2 nanoflakes-coated titanium dioxide (TiO2) nanoparticles layer serves as the electron acceptor with poly(3-helthiophene) (P3HT) as the hole conductor. The UV-visible spectroscopic measurement yields an optical bandgap of similar to 1.7 eV for the WS2 nanoflakes, confirming the presence of mixed monolayer/few-layers stack. Raman spectra of the WS2-coated TiO2 show a dominant peak at 140 cm(-1) for anatase TiO2, whereas peaks at 350 cm(-1) (in-plane vibration mode) and 420 cm(-1) (out-of-plane vibration mode) denote the signature of WS2 nanoflakes. Photovoltaic performance, electron transport, and recombination at TiO2/WS2/P3HT interfaces are explored through trap-assisted Shockley-Read-Hall model to elucidate WS2 as a potential material candidate for efficient solar energy harvesting. (C) 2012 Elsevier Ltd. All rights reserved.