Efficient quantum dot-sensitized solar cell with polystyrene-modified TiO2 photoanode and with guanidine thiocyanate in its polysulfide electrolyte

Monodispersed polystyrene (PS, ca. 300 nm) latex particles are incorporated into a TiO2 film. A polystyrene-modified TiO2 film (M-TiO2) with micro-cluster structure, containing micro/nano-composite pores is thus obtained after sintering. Cadmium sulfide (CdS) quantum dots (CdS-QDs) are accumulated over M-TiO2 and bare TiO2 films (B-TiO2) by successive ionic layer adsorption and reaction (SILAR); we designate these films as M-TiO2/CdS and B-TiO2/CdS, respectively. Influence of SILAR cycles used for depositing CdS on B-TiO2 and M-TiO2 films on the performance of the pertinent quantum dot-sensitized solar cells (QDSSCs) is studied. The QDSSC with 6 SILAR cycles of M-TiO2/CdS (M-TiO2/CdS6) exhibited a solar-to-electricity conversion efficiency (a) of 1.79%, while the cell with B-TiO2/CdS5 shows an eta of 1.35%, under the illumination of one sun. Moreover. guanidine thiocyanate (GuSCN) is found to be a promising additive to the polysulfide electrolyte. The additive renders higher conversion efficiency (2.01%) to its QDSSC. Durability of the CdS-QDSSC is also tested. Scanning electron microscopy (SEM) is used to obtain the images of TiO2 films and energy-dispersive X-ray spectroscopy (EDX) is employed to study the stoichiometric ratios of M-TiO2/CdS and B-TiO2/CdS. Incident photon-to-current conversion efficiencies (IPCE) of the QDSSCs are obtained to confirm the J(SC) behaviors of the cells. (C) 2011 Elsevier B.V. All rights reserved.