Design, fabrication and modification of metal oxide semiconductor for improving conversion efficiency of excitonic solar cells

• Design and fabrication of hierarchical nanostructured metal oxide semiconductors.
• Engineering interface chemistry can reduce the surface charge recombination.
• Recent work in excitonic solar cells was summarized.

Excitonic solar cells (ESCs) including dye-sensitized solar cells (DSCs), quantum dot-sensitized solar cells (QDSCs), perovskites solar cells (PSCs) and inverted organic photovoltaics (OPVs), are built upon metal oxide semiconductors (MOSs), which have attracted considerable attention recently and showed a promising development for the next generation solar cells. The development of nanotechnology has created various MOS nanostructures to open up new perspectives for their exploitation, significantly improving the performances of ESCs. One of the outstanding advantages is that the nanostructured mesoporous MOSs offer large specific surface area for loading a large amount of active materials (dyes, quantum dots or perovskites) so as to capture a sufficient fraction of photons as well as to facilitate efficient charge transfer. This review focuses on the recent work on the design, fabrication and surface modification of nanostructured MOSs to improve the performance of ESCs. The key issues for the improvement of efficiency, such as enhancing light harvesting and reducing surface charge recombination, are discussed in this paper.