Quantum Dot Technology in Solar Cells

In recent years, quantum dots (QDs) have emerged as an innovative approach in solar energy technology. These advanced materials increase solar cell efficiency with their properties such as light absorption over a wide spectrum of light, optimising electron transport and enabling multiple exciton generation.

Especially environmentally friendly derivatives such as carbon quantum dots (CQDs) and graphene quantum dots (GQDs) are preferred in various applications as promising options to respond to the increasing demand for electricity and to provide sustainable energy solutions. Nanografi, Türkiye's first nanotechnology company based in METU Technopolis, continues to contribute to the studies by producing quantum dots in green, blue and orange colours with high luminescent and performance in its advanced technology laboratories.

Introduction

Increased demand for electricity to power electronics, cars, and household energy sources has boosted the study of renewable or environmentally benign materials to improve solar cell efficiencies. As a result, pollution and high production costs have raised environmental and human health concerns, leading to intense interest in engineering multifunctional and economically viable advanced materials.

Solar Energy and Solar Cells

Solar energy is one of the most abundant and renewable energy sources available, with the sun providing an estimated 1.8 × 10¹⁴ kW of power to Earth’s surface annually. Traditional silicon-based solar cells have been instrumental in harnessing this energy, achieving efficiencies up to 24% in commercial settings. However, their production costs, material limitations, and efficiency ceilings (29.4% theoretical limit) have driven the search for alternative technologies.

Third-generation solar cells, including dye-sensitized solar cells (DSSCs), perovskite solar cells (PSCs), and QDSSCs, aim to overcome these barriers by introducing advanced materials and novel designs. Among these, QDs stand out for their ability to enhance light absorption, reduce recombination losses, and enable flexible and lightweight solar cell designs.

Quantum Dot Technology

Quantum dots (QDs) are nanoscale semiconductor particles that exhibit quantum confinement effects. Their small size gives them unique properties:

• Tunable Bandgaps: The size of quantum dots determines which wavelengths of light they absorb. By changing the size of these dots, it is possible to control which colours of light they ‘catch’. For example, you can set a smaller quantum dot to absorb blue light instead of red. This flexibility allows solar cells to generate energy more efficiently by capturing different colours (wavelengths) of sunlight more effectively.
• Multiple Exciton Generation (MEG): A special feature of quantum dots is that they can generate more than one energy carrier (electron-hole pair) when excited by a particle of light (photon). Normally, a photon produces only one energy carrier. Quantum dots, however, have the capacity to produce more than one carrier from the same photon. This means that more energy can be obtained from the same amount of sunlight, making the energy conversion of solar cells much more efficient.

Key types of QDs used in solar cells include:

Graphene Quantum Dots (GQDs):

Graphene quantum dots offer high conductivity, chemical stability and mechanical flexibility thanks to their carbon-based structure. These properties make them an ideal material, especially for portable solar cells. Thanks to their light weight and flexibility, they are frequently preferred in solutions for mobile and compact energy needs.

Carbon Quantum Dots (CQDs):

Carbon quantum dots stand out with their environmentally friendly and non-toxic structure. Their strong photoluminescence properties and low-cost production advantage make them suitable for sustainable solar technologies. In addition, they can be integrated into large-scale applications thanks to their scalability.

Metal Chalcogenides (e.g., CdSe, CdTe):

Metal chalcogenide quantum dots, such as cadmium selenide (CdSe) and cadmium telluride (CdTe), are characterised by their high light absorption capacity and efficient charge separation capabilities. These properties make them a common choice in quantum dot-sensitised solar cells and enable high-performance energy conversion.

Perovskite Quantum Dots (PQDs):

Perovskite quantum dots are characterised by their high quantum efficiency and tunable optical properties. Their enhanced stability makes them a favoured choice for solar cell applications. Such quantum dots promise groundbreaking innovations in solar cell technology in terms of both efficiency and durability.

Production and Developments

Modern synthesis methods such as hydrothermal, microwave-assisted and bottom-up approaches provide precise control over the size, composition and optoelectronic properties of quantum dots. With these methods, scalable production has become possible and the integration of quantum dot technology into solar energy systems has accelerated.

Use of Quantum Dots in Solar Cells

Quantum dots can be used in different parts of a solar cell to improve its performance:

• Active Layer: The layer that absorbs sunlight and converts it into electricity. Quantum dots can capture light across a wider spectrum, including UV and infrared light.
• Hole Transport Layer (HTL): A layer that moves positive charges (holes) efficiently. Graphene quantum dots make this layer more stable and effective.
• Electron Transport Material (ETM): A layer that moves electrons to generate electricity. Quantum dots improve electron movement, reducing energy losses.

Nanografi offers high-performance solutions for both scientific and industrial applications with graphene quantum dots synthesized in blue and green and carbon quantum dots engineered in orange.

Explore Nanografi's full range of quantum dot products now!

Conclusion

Quantum dot technology offers a revolutionary innovation in solar energy conversion, making it possible to overcome the limits of conventional photovoltaic systems. Thanks to their tunable optical properties, multi-exciton generation capacity and environmentally friendly structures, these advanced materials enable more efficient, sustainable and economical solar cell designs.

A wide range of materials, from environmentally friendly derivatives such as graphene and carbon to metal chalcogenides and perovskites, are being integrated into solar energy systems by facilitating their production with modern synthesis methods. These features increase energy efficiency for both portable devices and large-scale energy projects, making quantum dots an indispensable option for a sustainable energy future.

To learn about water-soluble quantum dots, lead sulphur quantum dots and much more, visit our Blografi now.

References

Panachikkool, M., & Pandiyarajan, T. (2023). Graphene quantum dots as game-changers in solar cell technology: a review of synthetic processes and performance enhancement. Carbon Letters 2023 34:1, 34(1), 445–475. https://doi.org/10.1007/S42823-023-00617-W

Singh, S., Khan, Z. H., Khan, M. B., Kumar, P., & Kumar, P. (2022). Quantum dots-sensitized solar cells: a review on strategic developments. Bulletin of Materials Science, 45(2), 1–13. https://doi.org/10.1007/S12034-022-02662-Z/FIGURES/8