Development of the molecular engineering of disazo dye sensitizers and TiO2 semiconductor surface to improve the power conversion efficiency of dye-sensitized solar cells

Abstract

Employing organic sensitizers is potentially advantageous in dye-sensitized solar cells (DSSCs) compared with ruthenium(II) complexes since they comprise earth-abundant elements and have high molar absorption coefficients and notable structural diversity. However, the molecular engineering of organic dyes is of great interest as they can be designed to maximize light harvesting. Herein, a family of disazo dye molecules containing multiple donor and acceptor groups with two π-spacer parts (AD1-AD5) was employed as photosensitizers to fabricate novel DSSCs based on modified TiO2 semiconductor (GNT/AD1-AD5). Modification of the TiO2 surface was carried out with doping of nitrogen and graphene into the titanium dioxide substrate. The effect of an extended π-conjugation system and linking groups of dye molecules in photovoltaic performance has been examined. Moreover, the power conversion efficiency has been compared in the case of utilizing two different redox mediators including iodine and cobalt-based electrolytes. GNT/AD4 with triiodide/iodide electrolyte achieved the highest solar to electrical energy conversion efficiency (η = 3.82%, VOC = 0.862 V), in the series.