Abstract
Determining an ideal adsorption configuration for a dye on the semiconductor surface is an important task in improving the overall efficiency of dye-sensitized solar cells. Here, we present a detailed investigation of different adsorption configurations of designed model dyes on TiO2 anatase (101) surface using first principles methods. Particularly, we aimed to investigate the influence of cyano group in the anchoring part of dye on its adsorption stability and the overall photovoltaic properties such as open circuit voltage, electron injection ability to the surface. Our results indicate that the inclusion of cyano group increases the stability of adsorption only when it adsorbs via CN with the surface and it decreases the photovoltaic properties when it does not involve in binding. In addition, we also considered full dyes based on the results of model dyes and investigated the different strength of acceptor abilities on stability and electron injection ability. Among the various adsorption configurations considered here, the bidentate bridging mode (A3) is more appropriate one which has higher electron injection ability, larger VOC value and more importantly it has higher dye loading on the surface.
Highlights
Methods for improving photovoltaic properties of dye-sensitized solar cells (DSSCs) has attracted considerable interest because of their potential advantages towards light harvesting such as high power conversion efficiency, low cost, less environmental issues[1,2,3,4,5]
The different adsorption configurations of dyes containing carboxylic acid together with cyano group on the semiconductor surface have investigated, and it has been shown that the dye adsorption via cyanoacrylic group increased the adsorption stability compared to carboxylic acid[36, 40,41,42,43]
Based on our previous studies[14, 17], we have designed a model dye which consists of 4-methoxy-N-(4-methoxyphenyl)-N-phenyl benzene amine (MPBA) as a donor, thiophene (T) as π-bridge, thienopyrazine (TP) as acceptor and COOH as an anchoring group
Summary
Determining an ideal adsorption configuration for a dye on the semiconductor surface is an important task in improving the overall efficiency of dye-sensitized solar cells. To improve the efficiency of DSSCs, many research works have been directed all over the world, which includes the molecular designing of dyes holding desirable characteristics[3] and finding the efficient counter electrode for the reduction of an electrolyte[20,21,22,23,24] Another key factor that controls the PCE is appropriate adsorption configuration for the dyes on the semiconductor surface. In the present study, we have designed the D-π-A type of dyes with COOH as an anchoring group and systematically investigated the effect of cyano group on all the possible adsorption configurations on the anatase TiO2 (101) surface and the photovoltaic properties using density functional theory methods. The impact of the designed dyes on the packing of adsorbed dye molecules on the oxide surface is investigated
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