Is it possible to merge the genomes of photosynthesizing and electron-transporting bacteria to make an electric cell?
What you're describing is a phototrophic biofilm microbial fuel cell! They're pretty neat. 

Essentially the sun powers the bacteria and the bacteria in the anaerobic side passes electrons through the graphite electrode to use oxygen at the cathode. There's another explanation here. You could also "unfold" cyanobacteria and layer them and you'd probably get an efficiency increase but the system would be pretty fragile. Compared to other MFCs, though, everything is fragile. Dirt even works(not very well, but it's dirt).