The research on dye-sensitized solar cells (DSSCs) is in the advanced stage today. The only concern observed so far has been regarding its stability and efficiency. Its power conversion efficiency can be increased by incorporating various methods and materials based on nanotechnology. Several attempts have been employed to develop advanced methods for eco-friendly, commercially viable, and sustainable DSSCs to minimize the energy crisis in the future. Photoanode is one of the essential components of DSSCs that can be modified using different nanostructures to enhance its efficiency. The TiO2 nanoparticlebased photoanode with gold and silver has proven to be potent materials for getting efficient DSSCs. The plasmonic and quantum confinement effects also play a vital role in efficiency enhancement. In this review, we discuss numerous attempts made by researchers in the last decade to modify the photoanode and their progress. We also look at different types of nanostructures, such as quantum dots, metal oxide doping, layered structures, nanocomposites, and thin film formation, that improve the efficiency of DSSCs. Several methods were reviewed to modify photoanodes to optimize electron transportation, light scattering, trapping power, surface area, and reduce charge recombination. The trend in the efficiency enhancement of DSSCs using TiO2, Au, ZnO, Ag, and graphene nanostructures-based photoanodes have been explored in great detail.

    Abstract
    1 Introduction
        1.1 Evolution of DSSCs
        1.2 Evolution of photoanode
    2 Basic phenomenon in DSSC
        2.1 Plasmonic effect
        2.2 Quantum confinement effect
    3 Nanomaterials of different types and dimensions
        3.1 Quantum dots
        3.2 Metal oxide doping
        3.3 Nanostructures formation
        3.4 Layers formation
        3.5 Thin film formation
        3.6 Reduced graphene oxide
        3.7 Nanocomposites
    4 Types of photoanodes in DSSC
        4.1 TiO2-based photoanode
        4.2 Au-based photoanode
        4.3 ZnO-based photoanode
        4.4 Ag-based photoanode
        4.5 Carbon-based photoanode
    5 Conclusion
    6 Future aspects
    References

• Yogesh Kumar(Department of Physics, Indian Institute of Technology (Indian School of Mines))
• Tushar Chhalodia(Department of Chemistry, Deen Dayal Upadhyaya College, University of Delhi)
• Paramjeet Kaur Gumber Bedi(Department of Physics, Deen Dayal Upadhyaya College, University of Delhi)
• P. L. Meena(Department of Physics, Deen Dayal Upadhyaya College, University of Delhi)