DEVELOPMENT OF COST-EFFECTIVE COMPONENTS FOR DYE-SENSITIZED SOLAR CELLS

Abstract

The commercialization of dye-sensitized solar cells (DSSCs) has been hindered by relatively low efficiency and comparatively high cost of the PV. Hence, further development of DSSC field heavily depends on the bringing down of its cost and improvement of its power converting efficiency. Therefore, we focused on the development of cost-effective methods and components for improving the power converting efficiency (PCE) of DSSCs. In our work we have demonstrated that it is possible to modify the photoanode by using a simple cost-effective technic of surface doping of TiO2 via soaking the photoanode in 50 mM In3+ aqueous solution with acidic pH. Indium surface doping of TiO2 film resulted in remarkable suppression of charge recombination and improvement of VOC (from 0.77 V of the reference undoped TiO2 sample to 0.80 V of In surface doped TiO2 sample) leading to 18% efficiency increase. The overall result is comparable with bulk In doped TiO2 solar cells and demonstrate effectiveness of surface doping technic. Moreover, we developed a new strategy of suppressing porphyrin dye aggregation in DSSCs which is based on axial complexation of central Zn metal of the porphyrin dyes with pyridine compounds via D-A bonding. This enables the use of long alkyl-chain free porphyrins that are economical and easier to synthesize compared to traditional analogs. Thus, a simple structured ZnP porphyrin dye axially coordinated with 4,4’-bipyridine ligand reduced dye aggregation on TiO2 surface and led to over 40 % improvement of cell PCE compared to uncoordinated ZnP sensitized cell. Finally, we have prepared several novel Pt-free counter electrodes from less expensive materials like orange fiber derived carbon embedded cobalt sulfide nanoflakes (OFC@CoxSy-300) and ternary Cu-Co-S sulfides (CuxCoySz-3 and CuCo2S4) which are prepared at lower temperature than Pt-based counter electrode. The developed new composite counter electrode OFC@CoxSy-300 based cell outperformed conventional Pt-based DSSCs by almost 7 % in power converting efficiency due to good electrocatalytic activity of the product. Solvothermally prepared ternary copper-cobalt-sulfides as CuxCoySz-3 and nanostructured flower-shaped CuCo2S4 counter electrodes demonstrated better electrocatalytic activity than Pt CE leading to improved fill factor and photocurrent. Thus 11 % and 14 % enhancements in PCE compared to Pt-based DSSCs were observed in solar cells made of CuxCoySz-3 and CuCo2S4, respectively. The CuCo2S4 CE demonstrated excellent stability during aging test for 1000 h.