Organic Solar Cells

Research trends on printable solar cells such as dye-sensitized solar cells, organic thin film solar cells, and perovskite solar cells are reviewed. The efficiency of the dye-sensitized solar cells and the organic thin film solar cells is now 15% and over 19%, respectively. The efficiency of the lead-based perovskite solar cells reached over 25% which is close to that of the Si solar cell, and the research target is shifting to the fabrication of the large modules and the module stability. Tin-based perovskite solar cells attract attention as the narrow bandgap perovskite solar cells with the bandgap of 1.0 eV. The efficiency is improved to 23–24%. To aim at further higher efficiency, perovskite tandem solar cells composed of perovskite/perovskite, perovskite/Si, and perovskite/CIGS are reported. The highest efficiency is over 33%. The mechanism of the charge separation and items to be solved is discussed.