Abstract: With the worldwide dependence on non-renewable fossil fuels and increasing concerns over their impact on our planet through greenhouse gas emissions finding an alternative source of clean energy is a global imperative. The solar energy is one source of renewable energy resources, and It has the highest potential to contribute substantially to the future of carbon-free power needs. Solar to hydrogen has attracted much attention in the past decade due to its abundance and the spotlessness of hydrogen as fuel for energy usage. However, practically the requirements to convert solar energy to hydrogen, require a stable photocatalyst that’s able to operate efficiently over a wide range of the UV-VIS spectrum. Organic semiconductors have been widely used in hydrogen evolution due to their earth abundance, aqueous stability, and optical absorption that can be tuned to the UV-VIS spectrum. In chapter 3, The effect of different sacrificial regents on hydrogen evolution activity was systemically investigated by using poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) nanoparticles dispersion large and small diameter with Sodium dodecyl sulfate (SDS) as stabilizer. Ascorbic acid (AA), diethylamine (DEA), triethanolamine (TEOA), and triethylamine mixed with methanol (TEA/MeOH) were chosen as sacrificial reagents. The results indicate that the large diameter give improved efficiency with ascorbic acid, and the small diameter improved activity in the presence of diethylamine. The results indicated that the comparison between different sacrificial reagents is difficult because, the conditions of every experiment is different to another, depending on (the type of photocatalyst used, solubility, activity..) so to date, there is no clear concurrence in which sacrificial reagent is better than others. Photocatalysts formed from a single organic semiconductor typically suffer from inefficient intrinsic charge generation, which leads to low photocatalytic activities. In chapter 4, To overcome this limitation, we have used BTR, O-IDTBR, and PC71BM in binary and tertiary heterojunction nanoparticles between non fullerene donors’ small molecules and fullerene acceptor. The resulting photocatalyst display unprecedentedly a high hydrogen evolution rate over 12000 μmolh-1g-1 under AM 1.5g illumination.