Quantum dots for solar cell applications

Over the last decade, quantum dot (QD)-sensitized solar cells (QDSSCs), as a promising candidate for the next generation solar cell (SC) technology, have gained significant attention. For the bulk or thin film SCs, one of the biggest lost occurs within a few picoseconds after the photon is absorbed, as a photon with energy larger than the semiconductor band gap produces charge carriers with excess kinetic energy, which is dissipated via phonon emission. Semiconductor QDs, due to their quantum confinement properties, provide a new pathway for controlling energy flow. Therefore, they have the potential to enhance the efficiency of the primary photoconversion efficiency. QDSSCs present promising cost-effective alternatives to conventional silicon SCs because of their outstanding properties, such as simplicity in fabrication, possibility to realize light absorption in wide solar spectrum regions, and theoretical conversion efficiency up to 44%. This chapter presents a thorough review on the recent progress in QDSSCs. It is divided into seven sections, starting with quantum confinement, multiple exciton generations, and molar extinction coefficient as a general theoretical background in SC. This is followed by an introduction to the operational principle in QDSSCs. The third part focuses on photoanode in QDSSCs, which cover the various QD materials, including graphene QDs used as light harvester, and the different deposition techniques such as chemical bath deposition, successive ionic layer adsorption and reaction, electrochemical deposition, electrophoretic deposition, and molecular linker attachment and direct adsorption. The counter electrodes in QDSSCs are reviewed in the fourth section, while an extensive study on the electrolytes used in QDSSCs is addressed in the fifth section. The experimental backgrounds in QDSSCs are discussed in the sixth section with a focus on current-voltage measurements and electrochemical impedance spectroscopy. The final section contains a brief summary of the discussed topics covering the future outlook and future perspectives of the QDSSCs.