AbstractA thiazine photoelectrochemical cell has been developed involving thiazine photo‐reduction using EDTA as the electron donor together with photosynthetic electron transport in chloroplasts to generate electricity with a higher power conversion efficiency than for thiazine‐EDTA alone. Thionine and methylene blue have been shown to be electron acceptors of Photosystem I. The cell employed had a high ratio of the area of chloroplast‐impregnated membrane compared to the volume of thiazine solution. This emphasised the photosynthetic contribution. An open circuit photovoltage (Voc) of 415 mV, a maximum power density (Pa) of 4.15 m̈W cm‐2, a short circuit current density (Isc) of 50 m̈A cm‐2and a power conversion efficiency (Sp) of 0.145% were observed using thionine as the electron acceptor compared to aVocof 383 mV, aPdof 3.0 m̈W cm‐2, andIscof 43.0 m̈A cm‐2and anpof 0.095% when methylene blue was used as the electron acceptor. These results show that the thiazine photogalvanic cell can be combined with the chloroplast solar battery in order to increase the power conversion efficie