Graphene quantum dots (GQDs) are zero-dimensional carbonous materials with exceptional physical and chemical properties such as a tuneable band gap, good conductivity, quantum confinement, and edge effect. The introduction of GQDs in various layers of solar cells (SCs) such as hole transport layer (HTL), electron transport materials (ETM), cathode interlayer (CIL), photoanode materials (PAM), counter electrode (CE), and transparent conducting electrode (TCE) could improve the solar energy (SE) harvesting, separation and transportation of electrons and hole, thus ultimately enhance the overall performance and stability of SCs. The incorporation of GQDs in various layers such as HTL, ETM, CIL, PAM, CE, and TCE achieved photo conversion efficiencies (PCEs) of 18.63, 21.1, 12.81, 9.41, 8.1, and 3.66%, respectively. Furthermore, GQDs improved stabilities such as resistance to degradation for HTL (up to 77%), ETM (80%), resistance to UV light for ETM (94%), resistance to temperature in ETM (90%), and bending stabilities after 1000 cycles for HTL (88%) and for TCE (90%). There are reviews focused on the utilization of different carbon-structured materials such as graphene, carbon nanotubes (CNT), fullerenes, and carbon dots in SCs applications. More specifically, the utilization of GQDs for SCs is limited and yet to be explored in greater detail. This review mainly focuses on the recent advancement of various techniques of production of GQDs synthesis, utilization of GQDs in various layers like HTL, ETM, CIL, PAM, CE, and TCE for the enhancement of PCE, and the stability of SCs. As a result, we believe that an exclusive study on GQDs-sensitized solar cells (GQDSSCs) could provide an in-depth analysis of the recent progress, achievements, and challenges.

Graphene quantum dots as game-changers in solar cell technology: a review of synthetic processes and performance enhancement
    Abstract
        Graphical abstract
    1 Introduction
    2 Photovoltaic cells
        2.1 Synthesis of GQD
            2.1.1 Top-down method
            2.1.2 Electrochemical exfoliation
            2.1.3 Hydrothermal
            2.1.4 Electron beam lithography
            2.1.5 Bottom-up methods
            2.1.6 Organic synthesis
            2.1.7 Cage opening of fullerene
            2.1.8 Microwave synthesis
    3 Hole transport layer
        3.1 Properties
        3.2 Progress and advancements
    4 Electron transport material
        4.1 Properties
        4.2 Progress and advancements
            4.2.1 Cathode interlayer (CIL)
    5 Photoanode materials (PAMs)
        5.1 Properties
        5.2 Progress and advancements
        5.3 Counter electrodes
            5.3.1 Properties
        5.4 Progress and advancements
    6 Transparent conducting electrode
    7 Conclusion
        7.1 Future aspects
    Acknowledgements 
    References

• Muhammad Panachikkool(Department of Sciences, Indian Institute of Information Technology Design and Manufacturing Kurnool, Kurnool, Andhra Pradesh 518008, India)
• T. Pandiyarajan(Department of Sciences, Indian Institute of Information Technology Design and Manufacturing Kurnool, Kurnool, Andhra Pradesh 518008, India) Corresponding author