This is based on two research papers "Developing an Ironcarbon nitride complex as photocatalyst with response to visible light" Yang et al and "Preparation and characterization of Metalfree graphitic Carbon Nitride Film Photocathodes for Lightinduced Hydrogen Evolution" Yang et al if you want to check them out. Making gC3N4 (Graphitic Carbon Nitride) is very easy. Just heat Urea to 550 degrees in a covered vessel and after 3 hours you will have gC3N4 just sitting there. You need to wash it in nitric acid to get rid of any remaining ammonia and water after that until the pH is neutral but that's all. After that Making a doped complex is equally easy. Once you have done that you are ready to make a solar cell. Hope it helps.