Journal of Materials Science and Nanomaterials
Open Access

Solar harvesting; Quantum dots; Lead-free materials; Efficiency optimization; Nanotechnology; Renewable energy; Eco-friendly synthesis; Energy conversion; Solar nanomaterials; Bandgap engineering; Photovoltaic devices; Environmental sustainability; Semiconductor nanocrystals; Colloidal synthesis; Optoelectronic properties; Non-toxic quantum dots; Solar cell innovation; Charge carrier dynamics; Quantum confinement; Advanced materials

Introduction

In the ongoing pursuit of sustainable energy solutions, solar harvesting stands as a vital component in the transition toward renewable energy sources. Conventional photovoltaic technologies, while effective, face challenges related to efficiency limitations, environmental toxicity, and cost. One of the most promising innovations in this field is the use of quantum dots (QDs)—semiconductor nanocrystals that exhibit size-tunable optical and electronic properties as a result of quantum confinement effects. A significant barrier to the widespread adoption of QDs has been the use of toxic heavy metals like lead and cadmium, which pose substantial environmental and health risks [1-5].

Recently, research has shifted toward the synthesis and application of lead-free quantum dots, which offer comparable performance without the associated toxicity. These emerging materials have the potential to significantly advance solar energy conversion through improved light absorption, tailored bandgaps, and enhanced charge carrier dynamics. This study focuses on the eco-friendly synthesis of lead-free quantum dots, the characterization of their optoelectronic properties, and the strategies for optimizing their performance in solar harvesting applications [6-10].

Lead-free quantum dots such as tin-based (SnS, SnSe), copper indium sulfide (CIS), and perovskite-derived nanocrystals have shown promise due to their low toxicity, tunable bandgap, and strong absorption properties. This work emphasizes scalable, cost-effective, and low-temperature solution-based synthesis methods, such as hot-injection and solvothermal techniques. Efficiency optimization strategies include surface passivation, ligand exchange, and the formation of heterojunction structures to reduce recombination losses and improve charge transport. The integration of these nanomaterials into photovoltaic architectures signals a major advancement in the design of sustainable solar energy systems.

Discussion

The transition from toxic to lead-free quantum dots has driven innovation in both materials synthesis and device architecture. Various synthesis methods, including colloidal techniques like hot-injection and microwave-assisted synthesis, have enabled the production of high-quality, monodisperse lead-free quantum dots with controlled crystallinity and morphology. Tin-based, bismuth-based, and copper-indium-based QDs have emerged as leading candidates due to their favorable electronic properties and environmental compatibility.

Optical absorption in these materials is tunable through particle size and composition, enabling better alignment with the solar spectrum. To enhance their performance in photovoltaic applications, surface passivation techniques are employed to reduce trap states and non-radiative recombination. Surface ligands, while necessary for colloidal stability, can impede charge transport; thus, short-chain ligand exchange strategies are used to improve conductivity. The construction of core-shell structures, such as a SnS core with a ZnS shell, can further enhance stability and luminescence efficiency.

From a device standpoint, integrating lead-free QDs into various solar cell configurations—such as quantum dot-sensitized solar cells (QDSSCs), heterojunction solar cells, and hybrid architectures—has shown progress. Enhancements in electron and hole transport layers, band alignment, and charge separation mechanisms are critical for improving power conversion efficiencies. Some of these configurations are now achieving competitive efficiencies, and continued optimization holds the promise of surpassing the Shockley–Queisser limit in tandem or multi-junction designs.

However, significant challenges remain. Stability under long-term illumination and environmental conditions, scale-up of production methods, and the intricate dynamics of charge transfer within QD-based devices require further study. Advanced characterization methods such as photoluminescence spectroscopy, transient absorption spectroscopy, and electron microscopy offer insights into the structural and electronic behavior of QDs and inform future optimization strategies. Life-cycle analysis and environmental assessments underscore the necessity and potential benefits of adopting lead-free QDs in future solar technologies.

Conclusion

Lead-free quantum dots represent a critical advancement in the field of solar energy harvesting, offering a sustainable and efficient alternative to traditional quantum dot materials. Through the development of environmentally friendly synthesis techniques and the application of advanced efficiency optimization strategies, these materials are poised to play a key role in the next generation of solar technologies. Tin-based and copper-indium-based quantum dots, among others, demonstrate favorable properties for photovoltaic use, including strong light absorption and tunable bandgaps.

Progress in surface engineering, core-shell nanostructures, and solar cell integration has contributed to increasing device performance, although challenges in stability, scalability, and charge dynamics persist. The ongoing refinement of material and device design, coupled with interdisciplinary collaboration, will be essential to realizing the commercial potential of lead-free QDs. As the demand for clean energy continues to grow, these innovative materials provide a promising pathway toward efficient and environmentally responsible solar power solutions.

References

1. Zhao D, Feng J, Huo Q, Melosh N, Fredrickson GH, et al. (1998) Triblock copolymer synthesis of mesoporous silica with periodic 50 to 300 angstrom pores. Science 279: 548-552.

   Indexed at, Google Scholar, Crossref

2. Johansson EM (2010) Controlling the pore size and morphology of mesoporous silica, Linkoping University PhD thesis.

   Google Scholar, Crossref

3. Lu B, Kawamoto K (2012) A novel approach for synthesizing ordered mesoporous silica SBA-15, Materials Research Bulletin 47: 1301-1305.

   Google Scholar, Crossref

4. Sing KSW, Everett DH, Haul RAW, Moscou L, Pierotti RA, et al. (1985) Pure and Applied Chemistry 57: 603-619.

   Google Scholar

5. Kamau JM, Mbui DN, Mwaniki JM, Mwaura FB (2018) Utilization of rumen fluid in production of bio- energy from market waste using microbial fuel cells technology. J Appl Biotechnol Bioeng 5: 227‒231.

   Indexed at, Google Scholar, Crossref

6. Kamau JM, Mbui DN, Mwaniki JM, Mwaura FB (2020) Proximate analysis of fruits and vegetables wastes from Nairobi County, Kenya. J Food Nutr Res 5: 1-8.

   Indexed at, Crossref

7. Kinyua A, Mbugua JK, Mbui DN, Kithure J, Michira I, et al. (2022) Voltage Recovery from Pesticides Doped Tomatoes, Cabbages and Loam Soil Inoculated with Rumen Waste: Microbial Fuel Cells. IJSRSET 9: 172-180.

   Indexed at, Google Scholar, Crossref

8. Kiyasudeen SK, Ibrahim MK, Ismail SA (2015) Characterization of Fresh Cattle Wastes Using Proximate, Microbial and Spectroscopic Principles. Am Eurasian J Agric Environ Sci 15: 1700-1709.

   Google Scholar, Crossref

9. Li Y, Jin Y, Borrion A, Li H, Li J (2017) Effects of organic composition on the anaerobic biodegradability of food waste. Bioresour Technol 243: 836-845.

   Indexed at, Google Scholar, Crossref

10. Mbugua JK, Mbui DN, Waswa AG, Mwaniki JM (2022) Kinetic Studies and Simulation of Microbial Fuel Cells Voltage from Clostridium Spp. and Proteus. J Microb Biochem Technol 14: 483.

    Indexed at, Crossref