In the realm of energy and materials science, a team of researchers from the Indian Institute of Technology Guwahati has made a significant stride in understanding and manipulating excitonic charge states in two-dimensional (2D) materials. The team, led by Debasish Biswasray, along with Yogendra Singh, Amar Jyoti Biswal, and Bala Murali Krishna Mariserla, has developed a novel approach to enhance the performance of 2D semiconductors, which could have profound implications for the energy sector, particularly in optical data storage, quantum-light, and display technologies. Their findings were recently published in the journal Advanced Materials.
The researchers focused on monolayer tungsten disulfide (WS2), a 2D semiconductor, and employed a unique doping technique using water-rinsed polyvinyl alcohol (PVA). This method allowed them to achieve efficient and reversible conversion between excitons and trions, which are quasiparticles that play a crucial role in the optical and electronic properties of semiconductors. Unlike conventional chemical doping techniques, this approach does not hinder the reversibility and density of excitonic charge states, making it a more effective solution.
To further enhance the quasiparticle densities, the team applied high periodic biaxial strain to the PVA-doped WS2 using a 2D silica microsphere array. This strain-induced funneling of the PVA-injected free electrons substantially increased the excitonic quasiparticle densities and boosted the trion emission by 41%. The method enables nearly 100% reversible trion-to-exciton conversion without the need for electrostatic gating, while delivering thermally stable trions with a large binding energy of approximately 56 meV and a high free electron density of around 3×10^13 cm^-2 at room temperature.
The practical applications of this research for the energy sector are promising. The ability to control and enhance excitonic charge states in 2D materials can lead to more efficient carrier recombination, tunable emission, and modulation of valley polarization. These properties are essential for developing advanced optical data storage devices, quantum-light technologies, and high-performance displays. Moreover, the versatility of this platform could extend to other 2D materials, opening up new avenues for innovation in the energy and electronics industries.
In summary, the research conducted by Biswasray and his team at the Indian Institute of Technology Guwahati presents a significant advancement in the manipulation of excitonic charge states in 2D materials. Their novel doping and strain application technique offers a versatile platform for enhancing quasiparticle densities, with potential applications ranging from optical data storage to quantum-light technologies and advanced displays. This work not only contributes to the fundamental understanding of 2D semiconductors but also paves the way for practical innovations in the energy sector.
This article is based on research available at arXiv.