Improved charge collection and photo conversion of bacteriorhodopsin sensitized solar cells coupled with reduced graphene oxide decorated one-dimensional TiO2 nanorod hybrid photoanodes

Nanohybrid photoanodes made of mixed phase TiO2 nanorods (NRs) decorated with reduced graphene oxide (rGO) is fabricated by one step hydrothermal technique. Addition of rGO influences the phase formation of the TiO2 and optimum mixed phase formation of rutile (16%) and anatase (84%) TiO2 polymorphs is achieved at 1.0 wt% rGO decoration. Using rGO decorated TiO2 hybrid photoanodes, bacteriorhodopsin sensitized solar cells is fabricated with liquid and quasi-state electrolyte. Decoration of 1.0 wt% rGO upon TiO2 NRs boosted the photocurrent (Jsc = 2.2 mA/cm2) generation and photoconversion (η = 1.3%) efficiency which is 94% enhanced than pristine TiO2 NRs photoanodes. Experimental observation showcase higher rGO decoration (>1.0 wt% rGO) suppress the charge transport due to the formation of self-induced trapping sites within the transfer network. Minimum charge transfer resistance and maximum charge collection efficiency of ∼98% is achieved at 1.0 wt% rGO decorated TiO2 nanorods photoanodes. The ideal decoration of rGO (1.0 wt%) in photoanodes significantly improves the bio-sensitizer loading, charge transfer, electron lifetime and reduces the recombination of the BSSCs. Thus nanohybrid (rGO-TiO2 NR) photoanode assembled BSSC exhibit higher photoconversion efficiency than earlier BSSCs fabricated with nanoparticle (P25 mixed-phase TiO2) and nanorod (rutile and anatase pristine TiO2) based photoanodes.