The development of bioelectrochemical assemblies for sustainable energy transformation constitutes an increasingly important field of research. Significant progress has been made in the development of semiartificial devices for conversion of light into electrical energy by integration of photosynthetic biomolecules on electrodes. However, sufficient long-term stability of such biophotoelectrodes has been compromised by reactive species generated under aerobic operation. Therefore, meeting the requirements of practical applications still remains unsolved. We present the operation of a photosystem I-based photocathode using an electron acceptor that enables photocurrent generation under anaerobic conditions as the basis for a biodevice with substantially improved stability. A continuous operation lifetime considerably superior to previous reports and at higher light intensities is paving the way toward the potential application of semiartificial energy conversion devices.