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Abstract
The paper presents a design and quantitative analysis for an efficient light-trapping structure (LTS) based on Photonic Crystals (PhC) to enhance the performance of thin-film GaAs solar cells. LTS consists of single planar Anti-Reflection coating (ARC) layer at the top assisted by 2D PhC diffraction grating and Distributed Bragg Reflector (DBR) having alternate dielectric layers at the back of the active layer. The structure has been optically analyzed for various absorption layer thicknesses and compared with Lambertian limits, and it has been shown that with optimization of the design carefully, significant enhancement in the cell efficiency will take place for the presented LTS, especially for the devices with very thin absorption layers (typically less than 1000 nm). Further, it is demonstrated that this efficiency enhancement is attributed to the improvement in photon absorption in the wavelength range for which active layer thickness itself is not sufficient for absorption. According to the simulation analysis, the proposed cell efficiency can be enhanced 3.5 times for a 100 nm cell with LTS, and this enhancement shrinks only to 1.5 times for 1500 nm cell. The analysis has shown that for thin cells, the contribution by the optimized LTS is the main reason behind efficiency enhancement whereas the contribution from ARC remains almost constant. The evaluation of the performance of the proposed structure concerning the angle of incident light and fabrication tolerances has also been done, indicating improved performance. The paper also presents the quantitative and comparative analysis of the proposed design with different compatible designs such as a cell having double layer ARC and a cell having pyramidal ARC with PhC as BR design. Their analysis also predicts that the LTS especially BR are more important for thinner active layer cells and the cell with a pyramidal ARC with PhC outperforms the other designs.
ACKNOWLEDGEMENT
The authors would like to acknowledge the DST-SERI project ESCPC (Grant FR/203C) for the research work.
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Notes on contributors
Nikhil Deep Gupta
Nikhil Deep Gupta is assistant professor with the Centre for VLSI and Nanotechnology at Visvesvaraya National Institute of Technology (VNIT), Nagpur, India. He received his BE degree (Hons.) from Rajasthan University, Jaipur, India in 2009 in the electronics and communication engineering. He received his MTech (Gold Medal) from Maulana Azad National Institute of Technology (MANIT), Bhopal, India in 2011. After that, he had worked as junior research fellow at Malaviya National Institute of Technology (MNIT), Jaipur, India in a Defense Research and Development Organization (DRDO), India sponsored project. He received his PhD degree from MNIT, Jaipur, India in the year 2017. Previously, he worked as assistant professor at Manipal University, Jaipur, India and post-doc fellow at CSIR-CEERI, Pilani, India. He was a recipient of Govt of India, DST-SERB National Post Doc Fellowship (NPDF) award. He authored more than 20 research papers. His areas of interest include thin film solar cells and their applications, opto-electronics, display technology, optical communication, photonic crystals and photonic crystal based devices.
Vijay Janyani
Vijay Janyani is professor with the Department of Electronics and Communication Engineering at Malaviya National Institute of Technology (MNIT), Jaipur, India. He obtained his bachelor’s and master’s degrees in engineering from Malaviya Regional Engineering College Jaipur with a Silver Medal and Gold Medal, respectively, and PhD from University of Nottingham, United Kingdom under Commonwealth Scholarship Scheme. He is a recipient of various awards such as the Derrick Kirk Prize of University of Nottingham United Kingdom for excellence in research and Career Award for Young Teachers of All India Council for Technical Education (AICTE), New Delhi. He has been a visiting faculty at Asian Institute of Technology Bangkok under faculty secondment scheme of Government of India. He is the coordinator from his Institute of the British Council sponsored Indo-UK collaborative research project on Microstructured Optical Fibers under UKIERI scheme. His current research interests include optical communication, solar cells, photonic crystals, nonlinear optoelectronics, all-optical systems, and numerical modeling. Email: [email protected]