The general principle of Quantum Dot Sensitized Solar Cells (QDSSCs) is similar to that of Dye-Sensitized Solar Cells (DSSCs). In QDSSCs, excitons are formed in quantum dots upon photoexcitation, and the charge separation occurs in the QD. Electrons are injected from the QD excited state into the conduction band of the nano-TiO₂ or ZnO, which eventually produces a photovoltaic effect. The QDs act as light-harvesting materials, absorbing solar energy, and generating electrons. The excited electrons are then transferred to the charge collection layer, where they are collected and used to generate electricity. The QDs used in QDSSCs have distinct optoelectronic features, such as thermal stability, facilely tunable absorption range, high absorption coefficient, multiple exciton generation possibility, and solution processability, which make them promising candidates for next-generation solar cells. Recent research has focused on improving the efficiency and stability of QDSSCs through various strategies, including the use of internal additive materials, surface passivation, and secondary deposition. A combination of materials and passivation methods has been studied for higher efficiency. (1)(2)

        One of the topics of QDSSCs is multiple exciton generation (MEG). MEG is a phenomenon that occurs in QDSSCs when a single photon generates multiple electron-hole pairs. MEG occurs when a single photon generates multiple electron-hole pairs in the quantum dots. The excited electron in the conduction band interacts with the hole it leaves behind in the valence band, creating multiple excitons. MEG can increase the energy conversion efficiency of QDSSCs, but extracting the energy from the multiexcitons can be difficult due to their short lifetimes. (3)

Researchers investigated the MEG efficiency in PbSe quantum dots. The study found that the MEG efficiency in PbSe quantum dots is about two times better than that in bulk PbSe. The researchers also found that thin films of electronically coupled quantum dots have shown promise in simple photon-to-electron conversion architectures. (3) In recent research, one of the most commonly used materials for QDSSCs is PbS. A new type of solar cell that uses PbS:Hg quantum dots to achieve an unprecedentedly high photocurrent density (JSC) of 30 mA/cm², resulting in a power conversion efficiency of 5.6% at one sun illumination. (4) New types of research are also emerging. The whispering gallery mode (WGM) for light trapping is a promising strategy for improving the efficiency of sensitized quantum dots. (5)

(1) https://doi.org/10.1016/j.mset.2023.05.001
(2) J. Phys. Chem. Lett. 2015, 6, 1, 85–99. https://doi.org/10.1021/jz502227h
(3) J. Phys. Chem. Lett. 2011, 2, 11, 1282–1288. https://doi.org/10.1021/jz200166y
(4) Sci Rep 3, 1050 (2013). https://doi.org/10.1038/srep01050
(5) Front. Mater., Volume 6 -2019 https://doi.org/10.3389/fmats.2019.00282