Purple Bacteria Reaction Center Based Solid State Bio‐Solar Cell With a Large Open Circuit Voltage

A novel solid state bio-solar cell is demonstrated based on a purple bacterial reaction center-light harvesting 1 complex (RC-LH1) that exhibits high quantum efficiency and long carrier lifetimes. We demonstrate that careful choice of transport layers enables a high open circuit voltage of up to 0.3 V in these solid state biophotovoltaic devices. Electronic processes were investigated with impedance spectroscopy. Equivalent circuit modelling of impedance spectra obtained under illumination at DC offset voltages between open circuit and short circuit conditions revealed two relaxations on microsecond and millisecond time scales that are attributed to the charge transit time and carrier recombination processes, respectively. The operational stability of the solar cells was examined under constant illumination for over 3 hours and a burn-in time of several minutes was observed, after which operational parameters stabilized. This work is the largest voltage reported for RC-LH1 based solid state biophotovoltaic devices to date.