Volker Hartmann immobilizes and electrically contacts Photosystem 2 (PS2) from the thermophilic cyanobacterium Thermosynechococcus elongatus in a phenothiazine-modified redox polymer on an electrode surface. It is used there as an anodic half-cell in a semi-artificial, light-driven biobattery for the future generation of electrical power and biohydrogen. By selecting an appropriate polymer and optimizing the electrode preparation, the potential can be adjusted to that of the acceptor side of PS2, resulting in an 80-fold improvement compared to the previously existing system.