Photoanode modification of dye-sensitized solar cells with Ag/AgBr/TiO2 nanocomposite for enhanced cell efficiency

Abstract

Ag/AgBr compounds are well renowned visible light photosensitizers with inherent stability issues due to decomposition of the halide to metallic silver under illumination. However, when loaded onto a wide bandgap semiconductor with a more positive conduction band (i.e. TiO2) than that of AgBr, they become much more stable after some initial decomposition. Stabilization occurs due to transfer of extra electrons that could combine with interstitial Ag+ to form Ag0 clusters to the wide bandgap semiconductor. Even though Ag/AgBr/TiO2 nanocomposites are widely used in photocatalytic applications, their use in dye-sensitized solar cells have not been reported to date. In this work we incorporated an Ag/AgBr/TiO2 nanocomposite which was successfully synthesized via a one-pot synthesis procedure to DSC active material and obtained an enhanced power conversion efficiency (PCE) of 8.46%. The increase in PCE is an impressive 31% compared to the PCE of 6.45% of the reference cell made with P25 TiO2. The enhanced efficiency can be attributed to the synergistic effects rendered by both AgBr and metallic Ag. AgBr is highly efficient in generating electron – hole pairs under ≈ 470 nm visible light. Plasmonically enhanced effects introduced by Ag nanoparticles further improve the charge generation and separation both in the dye and AgBr. These cumulative effects combined with the stability maintained by the TiO2 matrix of the DSC active material results in an efficiently performing DSC due to the incorporation of Ag/AgBr/TiO2 nanocomposite into the photoanode.