**5. Summary**

The third-generation-sensitized solar cells have proved that they have the potential to compete with the conventional silicon based photovoltaics. The use of cheap materials with high performance make third-generation-sensitized solar cells a bright candidate as a future photovoltaic technology compared to other third-generation solar cells. The sensitized photovoltaic started with the emergence of DSSC using mesoporous nanocrystalline TiO2 sensitized with the ruthenium based dye molecule. Since then, the molecular engineering of the dye molecules are extensively studied to improve the DSSC performance. The sensitizer used in the photovoltaic device evolved from organic (dye) to inorganic (quantum dot) and hybrid organic-inorganic (perovskite) sensitizer. The tuneable energy band gap of quantum dots enables them to produce multiple electron-hole pairs per photon. The progress in the performance of perovskite solar cells is very promising. In the beginning, the efficiency of the perovskite solar cell was less than 4%. The efficient reached around 20% within less than 10 years. However, the stability and toxicity issues of lead have to be solved before they can be commercialized. Tin-based perovskite solar cell is already under investigation to replace the toxic lead.
