Optimizing CdS intermediate layer of CdS/CdSe quantum dot-sensitized solar cells to increase light harvesting ability and improve charge separation efficiency

CdS and CdSe quantum dots are commonly used together as co-sensitizers for quantum dot-sensitized solar cells, and CdS QDs are usually deposited on TiO2 films as an intermediate layer to facilitate the subsequent deposition of CdSe QDs. A modified Successive Ionic Layer Adsorption and Reaction (SILAR) technique with the addition of a triethanolamine (TEA) additive into a cationic precursor solution was utilized to optimize the CdS intermediate layer to enhance the performance of the obtained CdS/CdSe co-sensitized solar cells. Due to the increased light harvesting ability as well as the improved charge separation efficiency, our solar cell with a TEA-CdS interlayer demonstrated an enhanced power conversion efficiency with an improved short-circuit current and an increased open-circuit voltage. Utilizing a newly reported counter electrode based on CuS formed on a Ti sheet, the eventual power conversion efficiency of TEA-CdS/CdSe QDSSC was further improved to as high as 5.70%.