Photoelectrochemical studies of sensitized solar cells: sensitization of TiO2 with ruthenium complexes and cadmium seleno-sulfides

Photoelectrochemistry (PEC) of dye- and semiconductor sensitized solar cells is studied. In the first part, the structural effect of terpyridine (tpy) and dipirazinilpyridine (dpp) sensitizing dyes on the performance of solar cells is investigated. Mesoporous thin films of TiO2 on conductive glass are sensitized with carboxylic or ester functionalized tpy and dpp ruthenium dyes. The solar conversion behavior of all dyes is investigated based on the results obtained from PEC, incident photon to current efficiency (IPCE), electrochemistry and also optical techniques such as FTIR, UV-Vis and fluorescence. PEC efficiencies of up to 1.56% are achieved by tpy dye named H2 when used in a cell with a plain l-/l3- electrolyte. The effect of the additives in the electrolyte on the behaviour of the dyes is also studied and it is shown that due to the change of the location of the conduction band (CB) of TiO2 in the presence of these additives, the electron injection efficiencies of the dyes changes and directly translates in to lower efficiency values. In an independent but related study on dye-sensitized solar cells (DSSC), a new class of siliconized triaryalmine compounds are used as hole transport material (HTM) to replace the conventional l-/l3- electrolyte. These compounds increase the gained photovoltage (Voc) of the device up to 1 V which is an exceptional development in the field of DSSCs based on HTMs. Open-circuit photovoltage decay studies are employed to address the issues with respect to large recombination with these compounds in a solar cells. In the last part of my research, the effect of the preparation techniques of cadmium seleno-sulfides (CdSeS) on the performance of semiconductor-sensitized solar cells (SSSCs) is studied. TiO2 films are sensitized with different compositions of CdSexS1-x where x stands for the molar ratio of Se in the structure of the sensitizer. The sensitization is performed by chemical bath deposition in NH3 and sodium trinitriloacetate (NTA) solution and the effect of the performance of the resulting cell is related to the structure of the sensitizer deposited through each chemical bath. PEC and optical techniques are used to fulfill this purpose