Enhanced performance by heteroatom-doped reduced graphene oxide-TiO2-based nanocomposites as photoanodes in dye-sensitised solar cells

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.

Automated summary

This study compared the photoanode performance of boron- or nitrogen-doped reduced graphene oxide (B- or N-rGO) nanocomposites integrated with TiO2. N-rGO-TiO2 exhibited the best performance, demonstrating enhanced electron transportation and collection rates. Utilizing N-rGO-TiO2 as the photoanode material can improve the efficiency of DSSCs.