Increased Open Circuit Voltage Using Copper-Based Oxide Semiconductors as Photocathodes in p-Type Dye-Sensitized Solar Cells

The first reported dye-sensitized solar cells (DSSCs) known as photoanode dye-sensitized solar cells (n-DSSCs) or Grätzel cells operate via exciting dye electrons and electron injection through an n-type semiconductor (TiO2). The next generation of DSSCs including p-DSSC (photocathode DSSCs) and pn-DSSCs (tandem DSSCs) were designed to boost photovoltaic performance, efficiency and open circuit voltage (VOC) of DSSCs [1,2]. This thesis concerned a strategy to improve the open circuit voltage (VOC) of p-type dye-sensitized solar cells (p-DSSCs), with a focus on designing novel p-type semiconductors to use instead of NiO (as the most common and popular p-type semiconductor using in p-DSSCs and pn-DSSCs). To achieve this target, copper-based oxides (particularly those with delafossite structures) are attractive choice, because these semiconductors tend to provide reasonable transparency and hole mobility due to their own large band gap and specific orbital configuration of Cu+ respectively. In terms of getting higher VOC in p-DSSCs, a suitable valence band edge for semiconductor part can be considered as deep as possible, but not deeper than the HOMO level of sensitizer (dye), to create a driving force for charge transfer between a photoexcited dye and VB of semiconductor.