p-Type Dye-Sensitized Solar Cells Based on Delafossite CuGaO2 Nanoplates with Saturation Photovoltages Exceeding 460 mV

Exploring new p-type semiconductor nanoparticles alternative to the commonly used NiO is crucial for p-type dye-sensitized solar cells (p-DSSCs) to achieve higher open-circuit voltages (Voc). Here we report the first application of delafossite CuGaO2 nanoplates for p-DSSCs with high photovoltages. In contrast to the dark color of NiO, our CuGaO2 nanoplates are white. Therefore, the porous films made of these nanoplates barely compete with the dye sensitizers for visible light absorption. This presents an attractive advantage over the NiO films commonly used in p-DSSCs. We have measured the dependence of Voc on the illumination intensity to estimate the maximum obtainable Voc from the CuGaO2-based p-DSSCs. Excitingly, a saturation photovoltage of 464 mV has been observed when a polypyridyl Co(3+/2+)(dtb-bpy) electrolyte was used. Under 1 Sun AM 1.5 illumination, a Voc of 357 mV has been achieved. These are among the highest values that have been reported for p-DSSCs.