Influence of nanocrystal size on the quantum dots sensitized solar cells' performance with low temperature synthesized CdSe quantum dots

The CdSe quantum dots (QDs) were synthesized with ethanol and glycerol under 50-160 °C in the present work. The reaction temperature is lower than the traditional solvent thermal method to fabricate the CdSe QDs around 250-350 °C. What's more, the avoiding of the use of phosphine contained solvent make the whole reaction environmental friendly. Then 3-Mercaptopropionic (MPA) was used to exchange the CdSe QDs' ligand of olic acid. After that, the MPA-capped CdSe QDs were tethered onto the TiO2's substrate, which guarantee the high coverage of the CdSe QDs on the TiO2 photoanode and the absorption range of 450-560 nm of light harvest. Furthermore, through the results of the CdSe QD's size for the cells' performance, we compared the significance of the QDs' absorption range, the electron injection from the conduction band of CdSe QDs' to TiO2's and polysulfide to the valance band of the CdSe QDs in the cells' performance and discuss the mechanism to improve the efficiency of the QDSCs. Finally, the QDSCs with polysulfide solution and Cu2S as counter electrode show excellent cell performance with open-circuit voltage (Voc) of 0.6 V, short-circuit current density (Jsc) of 10.58 mA/cm2, fill factor (FF) of 0.564, and PCE of 3.7%.