Abstract
A comparative assessment of nanowire versus nanoparticle-based ZnO dye-sensitized solar cells (DSSCs) is conducted to investigate the main parameters that affect device performance. Towards this aim, the influence of film morphology, dye adsorption, electron recombination and sensitizer pH on the power conversion efficiency (PCE) of the DSSCs is examined. Nanoparticle-based DSSCs with PCEs of up to 6.2% are developed and their main characteristics are examined. The efficiency of corresponding devices based on nanowire arrays (NW) is considerably lower (0.63%) by comparison, mainly due to low light harvesting ability of ZnO nanowire films. The dye loading of nanowire films is found to be approximately an order of magnitude lower than that of nanoparticle-based ones, regardless of their internal surface area. Inefficient anchoring of dye molecules on the semiconductor surface due to repelling electrostatic forces is identified as the main reason for this low dye loading. We propose a method of modifying the sensitizer solution by altering its pH, thereby enhancing dye adsorption. We report an increase in the PCE of nanowire DSSCs from 0.63% to 1.84% as a direct result of using such a modified dye solution.
Highlights
IntroductionDye-sensitized solar cells (DSSCs) are regarded as a promising option to conventional solid-state semiconductor solar cells due to their low cost, ease of fabrication and environmental friendliness
Dye-sensitized solar cells (DSSCs) are regarded as a promising option to conventional solid-state semiconductor solar cells due to their low cost, ease of fabrication and environmental friendliness.DSSCs sensitized with Ruthenium-based complexes have achieved maximum power conversion efficiency (PCE) of 11.9% [1,2]
A systematic study of the parameters that affect the performance of nanowire-based DSSCs was conducted to investigate the underlying issues that prevent these devices from achieving PCEs close to those of nanoparticle-based DSSCs
Summary
Dye-sensitized solar cells (DSSCs) are regarded as a promising option to conventional solid-state semiconductor solar cells due to their low cost, ease of fabrication and environmental friendliness. DSSCs sensitized with Ruthenium-based complexes have achieved maximum power conversion efficiency (PCE) of 11.9% [1,2]. In DSSCs, the conversion of visible light to electricity is achieved through the spectral sensitization of wide bandgap semiconductors such as TiO2 , ZnO, SnO2 , NiO, etc. ZnO has attracted a great deal of interest in DSSCs applications, as a semiconductor with a wide band gap of 3.37 eV and a high exciton binding energy of 60 meV. ZnO has high room temperature carrier mobility (115–155 cm V−1 s−1 ), which enhances the performance of solar cells by reducing electron recombination [10]
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