Efficient Nanostructured Biophotovoltaic Cell Based on Bacteriorhodopsin as Biophotosensitizer

Abstract

Here, we report on utilizing a photoactive protein, bacteriorhodopsin (bR), as a light harvester in combination with TiO 2 nanoparticles in biosensitized solar cell application. Experiments have been conducted to investigate the capability of surface adsorption of bR on nanoparticular TiO 2 photoanodes. Different pretreatment processes have been done to modify the interface of TiO 2 nanoparticles and bR as a biophotosensitizer. Our results indicate the feasibility of efficient immobilization and photoinduced charge transfer of bR to the nanostructured TiO 2 photoelectrode. Under illumination of simulated AM1.5 sunlight, the solar-light-to-electricity conversion efficiency of the designed solar cell, composed of nanoparticular and nanofibrous layers, reached up to 0.35%, with an open circuit voltage of 533 mV and photocurrent density of 1 mA cm −2 . This optimized design of our bR-sensitized solar cell shows superior energy conversion efficiency in comparison to previously reported studies.

Bio-nano hybrid materials based on bacteriorhodopsin: Potential applications and future strategies

“…The major advantages of the bR include [22][23][24][25]: (1) Various mutants of bR have been reported to be used in bioelectronics as well as the native one [26][27][28][29]. Two classes of bR mutants have been suggested for solar cell application [30].…”

“…In bR based BSSCs, the photoanode is made of a porous semiconductor nanoparticles (mainly TiO 2 or ZnO NPs) sensitized with bacteriorhodopsin protein [22,46].…”

“…The CB of TiO 2 is located at a lower energy level than the lowest occupied molecular orbital (LUMO) of the bR molecule, so injection of the photoelectrons from bR to TiO 2 is energetically favorable [22]. The electrons migrate to the counter electrode through the external circuit.…”

“…The electrons migrate to the counter electrode through the external circuit. The oxidized bR accepts electrons from the electrolyte, regenerating the ground state ( Figure 2) [22,28].…”

“…is an appropriate substrate to immobilize bR, a low IEP protein, by electrostatic interactions with high binding stability [46]. On the other hand, loading the nanostructured photoelectrode with more than one layer of bR can significantly decrease the charge transfer rate in the TiO2/bR interface [22]. Therefore, higher efficiency of the photovoltaic cell can be ascribed to immobilization of LB monolayer of bacteriorhodopsin on the ZnO nanoparticulate film as well as those intrinsic features of ZnO thin film.…”