Enhanced performance by heteroatom‐doped reduced grapheneoxide‐TiO₂‐based nanocomposites as photoanodes in dye‐sensitised solar cells

Abstract

Summary The photoanode in a dye‐sensitised solar cell (DSSC) plays a crucial role in achieving a high power conversion efficiency (PCE). It supports the sensitiser and acts as a transporter of photo‐excited electrons from the sensitiser to the external circuit. These two functions are enhanced by a large surface area and a fast charge transport rate. Typically, the photoanode consists of titanium dioxide (TiO2) nanoparticles. If the nanoparticles are deposited on a carbonaceous substrate, it facilitates the transport of photogenerated electrons. This study compared the photoanode performance of boron‐ or nitrogen‐doped reduced graphene oxide (B‐ or N‐rGO) nanocomposites integrated with TiO2. All nanocomposites exhibited mainly the anatase TiO2 phase, and N‐rGO‐TiO2 exhibited the lowest bandgap of 2.1 eV, which was attributed to the formation of Ti‐O‐C and Ti‐O‐N bonds. Also, N‐rGO‐TiO2 displayed good charge carrier separation ability and electron transfer. The low TiO2 content in the nanocomposites led to the suppression of electron‐hole recombination, reduction in the bandgap energy and improvement in electron transport, resulting in higher current density. Two photo‐harvesting dyes (sensitisers) were investigated, that is, eosin B and Sudan II. A higher light‐harvesting efficiency was obtained from eosin B, indicating the presence of more dye molecules anchored onto the TiO2. Photoanodes fabricated from N‐rGO‐TiO2 and B‐rGO‐TiO2 showed enhanced photo‐exciton generation, higher short‐circuit current densities and significantly better PCEs of 3.94% and 2.55%, respectively, than their undoped rGO‐TiO2 counterparts (1.78%). This work demonstrates that heteroatom‐doped rGO‐TiO2‐based nanocomposites can improve the rate of transportation and collection of electrons, thereby enhancing the performance of DSSCs.

3D graphene: synthesis, properties, and solar cell applications

“…Various approaches have been explored to incorporate 3D graphene materials into a semiconductor (typically TiO 2 ) to form composite photoanodes, including reduction of GO 98–101 and CVD 47,102–104 approaches. For example, it was demonstrated that the introduction of rGO into TiO 2 in a photoelectrode increased the PCE by 55.3%.…”