Research: Flexible Photovoltaics and Light-trapping in Photonic Crystals

My present research focuses on photonic crystal (semiconductor of light) mediated strong light-matter interaction. Photonic crystals are periodic structures, capable of controlling the flow of light in unprecedented ways. While most of the applications of photonic crystal rely on the suppression of Electromagnetic density of states (in other words, existence of photonic band-gap), a suitably designed photonic crystal can greatly increase Electromagnetic density of states over a specified spectral range and thus, acts as a very efficient light-trap enabling a number of applications.

In a recent research based on this principle, I, along with Prof. Sajeev John, have proposed a new paradigm of high-efficiency silicon solar cell design that exploits the wave nature of sunlight. This design enables power conversion efficiency beyond 30%, using a 15 micron-thick, flexible, photonic crystal silicon sheet. Wave-interference in photonic crystals provides a new mechanism for solar energy capture, outside the framework of conventional ray-optics-based light trapping. Photonic crystal cell, 10-15 times thinner than the world-record-setting solar cells, enables thin-film silicon to leapfrog ahead of competing technologies and well beyond the efficiency of any single material cell of any thickness. Already, a number of industries have taken interest in this research and we are looking at an exciting time ahead!

Publications

Journals

• M. L. Hsieh, A. Kaiser, S. Bhattacharya, S. John and S. Y. Lin, “Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals”, Scientific Reports, 10, 11857 (2020)

• S. Bhattacharya and S. John, “Photonic crystal light trapping: Beyond 30% conversion efficiency for silicon photovoltaics”, APL Photonics Vol. 5, 020902 (2020), [Invited "Perspective"]

• S. Bhattacharya and S. John, “Beyond 30% Conversion Efficiency in Silicon Solar Cells: A Numerical Demonstration”, Scientific Reports, Vol. 9, 12482 (2019)

• S. Bhattacharya, I. Baydoun, M. Lin and S. John, “Towards 30% power conversion efficiency in thin-silicon photonic-crystal solar cells”, Physical Review Applied, Vol. 11, 014005 (2019)

• M. L. Hsieh, S. Y. Chen, A. Kaiser, Y. J. Yan, B. Frey, I. Bhat, R. Dahal, S. Bhattacharya, S. John and S. Y. Lin, “A low cost and large-scale synthesis of 3D photonic crystal with SP2 lattice symmetry” , AIP Advances, Vol. 9, 085206 (2019) [selected as Editor's Pick]

• S. Bhattacharya and S. John, “Designing High-Efficiency Thin Silicon Solar Cells Using Parabolic-Pore Photonic Crystals”, Physical Review Applied, Vol. 9, 044009 (2018) [selected as Editors' Suggestion]

• P. Kuang, S. Bhattacharya, M.L. Hsieh, S. John and S. Y. Lin, “Photonic crystals with a continuous, Gaussian-type surface profile for near-perfect light trapping”, SPIE Journal of Nanophotonics, Vol. 12, 026011 (2018)

• S. Bhattacharya and K. Shah, “Dispersion relation and self-collimation frequency of spoof surface plasmon using tight binding model” , Journal of Optics, Vol. 17, 065102 (2015)

• S. Bhattacharya and K. Shah, “Multimodal propagation of the electromagnetic wave on a structured perfect electric conductor (PEC) surface”, Optics Communications, Vol. 328, 102–108 (2014)

Conferences

• Y. Kalepu, S. Bhattacharya and U. K. Khankhoje, “Algebraic reconstruction techniques for inverse imaging”, accepted in ICEAA-IEEE APWC 2016, Cairns, Australia

• S. Bhattacharya and K. Shah, “On the characteristics of spoof surface plasmon in the high frequency limit”, PIERS 2015, Prague, Czech Republic

• S. Bhattacharya and K. Shah, “Pitfalls in the analogy between spoof surface plasmon and surface plasmon polariton”, 12th International Conference on Fiber Optics and Photonics, Kharagpur (India), OSA Technical Digest, paper S5A.47, 2014 (awarded SPIE Best Student Paper)