Photovoltaic group at CSIR-NPL is the oldest photovoltaic group in the country and has very rich history in silicon based photovoltaics since last five decades, being first to develop silicon solar cells in the country in around mid 70’s. CSIR-NPL is the first laboratory to demonstrate the complete process, from metallurgical grade silicon to solar grade polysilicon and fabrication of solar cells. Currently, the group is involved in basic and applied research spanning from wafer based silicon photovoltaic technology, thin film to latest concepts such as organic and perovskites, organic/inorganic heterostructures, based solar cells development, testing and measurements. Besides, the group is actively involved in the development of waste management technologies such as recycling of waste solar modules, plastic wastes and other electronic wastes for their societal applications.

The photovoltaic metrology group is involved in basic and applied research spanning from wafer based silicon photovoltaic technology, thin film to latest concepts such as organic and perovskites based photovoltaic devices development, testing and measurements. The group is currently engaged in the following R&D activities with an aim to develop efficient and cost effective photovoltaic materials and devices, to develop protocols for precise and accurate measurements of PV cells and modules as well as generating skilled manpower for supporting Indian PV sector.

• Photovoltaic Metrology: Setting national primary standard for solar cell calibration, secondary cell standard and national centre for photovoltaic module testing
• Validation of solar cell efficiency
• Silicon-based Photovoltaics: Unit process development for addressing optical, electronic and electrical losses
• Thin Film Photovoltaics: Nano-crystalline silicon and perovskites/silicon heterojunction solar cells
• Organic photovoltaic devices
• Perovskites photovoltaic devices
• Materials development of organic and perovskites solar cells
• PV Modules: Performance analysis, energy yield and degradation related investigations specific to Indian climatic conditions
• Training Programmes: Solar photovoltaic systems, fundamentals, design and metrology
• Recycling of end-of-life silicon photovoltaic cells and modules.

Ongoing Projects:
1. National primary standard facility for solar cell calibration; Sponsored by Ministry of New and Renewable Energy (MNRE), Govt. of India.
2. Development of interface layer of perovskite solar cells in view of silicon-perovskite tandem solar cell fabrication, Funded by DST.
3. Recycling of Plastic and its Applications in Road Construction Funded by CSIR (in collaboration of CSIR-CRRI).
4. Bulk preparation of p-type and n-type materials for excitonic solar cells, Funded by DST.
5. Design and development of flexible large area 156×156 mm2 modified perovskite mini modules, Funded by DST.
6. Project on training: Workshop and Training on PV materials, devices and systems sponsored by MNRE.

Projects executed/accomplished (Recent past):
1. Development of Efficient Silicon Photovoltaic Solar Cell (CSIR Network Project under TAPSUN programme) (2012-2017)
2. Novel approaches for Solar Energy Conversion (FlexiSolar) (CSIR Network Project under TAPSUN programme) (2012-2017)
3. R&D on thin film solar cells, Funded by MNRE (2011-2017)
4. Advancing the efficiency and production potential for Excitonic solar cells (APEX) Phase II, (International Network Project, Indo-UK) 04.09.2015 to 28.02.2018
5. Development of New Interfacial Layers for Efficient and Stable Excitonic Solar Cells sponsored by SERI, DST, New Delhi from 06/07/2017 to 05/07/2020.
6. Semiconducting Thiophene Based Electronic Materials for Organic Solar Cells sponsored by SERB, DST, New Delhi 07/10/2015 to 06/10/2018.
7. Development of silicon nanowire arrays for effective light harvesting and efficient solar cells; 2014-2019 under CSIR under Young Scientist awardee research grant.
8. Development of Flexible Perovskite Solar Cells sponsored by CSIR through a CSIR-YSA research grant (2016-2021).

Silicon Photovoltaic

The group is working on setting-up apex level testing and calibration facilities for solar cells at CSIR-NPL, the group is actively involved in basic and applied research on different silicon solar cell concepts spanning from wafer based silicon photovoltaic technology including the advanced structures such as black silicon based cells employing excellent light trapping schemes based on nanostructured silicon surfaces, to latest third generation PV concepts such as organic polymer and silicon heterostructures based PV devices, advanced passivation scheme like ALD-Al2O3 based passivation for Passivated Emitter Rear Contact (PERC) structured solar cells and thin/flexible silicon solar cells (<50 microns). The major focus is to develop efficient and cost effective photovoltaic devices/concepts. In the recent past, the group has got expertise in development of value added unit processes (Reflectance and Recombination losses) for high efficiency solar cells development, Standard BSF cell & Passivated Emitter and Rear Contact (PERC) cell.

• The group has developed and demonstrated Proof of concepts for black Si (both mono- and multi-crystalline) solar cells (>17% black silicon solar cells on156x156 mm2).
• The group has also developed processes for silicon surface passivation on p- and n-Si using atomic layer deposition (ALD) deposited Al2O3 film (realized surface recombination velocity <10 cm/s vis-à-vis best reported 1-5 cm/s) as well as ultra thin silicon oxide layer by economic wet chemical route which can also be used as tunnel layer at the back side of the solar cells for efficient charge collection and hence improved efficiency.
• Highly efficient PEDOT:PSS/Si HSCs is demonstrated via an effective surface micro-engineering of the as-cut, low-cost solar-grade thin Si wafers, an aspect rarely addressed before. The HSCs with photo-conversion efficiency >12.25% have been achieved.

Presently, selected research topics of the group include:

• Establishment of national primary standard facility for solar cell calibration and its dissemination to Indian PV industry, R&D organizations and academia.
• Novel light trapping schemes, surface and bulk passivation, ultra-thin layers and new materials for passivated contacts for silicon solar cells.
• Integration of value added unit processes to develop process technology for efficient solar cell using black Si and PERC concepts.
• Development of organic/silicon heterojunction based efficient hybrid solar cells
• Development of flexible solar cells (thinner wafer, <50 microns) for cost effective silicon PV technology
• Recycling of waste silicon solar modules

Thin Film Solar Cells

Silicon Thin Film Photovoltaic (Si-TFPV) activity of CSIR-National Physical Laboratory is one of major laboratory of India for the development of silicon thin film photovoltaic research since many years. In recent past, the group has developed very high frequency (60 MHz & 27.12 MHz) PECVD process for the high rate deposition of nano-crystalline silicon (nc-Si:H) thin films. In addition to increasing deposition rates, reducing non-uniformity and minimizing initial light induced degradation of nc-Si:H thin film layers was also aimed. The optimized p-i-n layers of nc-Si:H were deposited in separate chambers on glass & TCO coated glass substrates (2.5×2.5 cm2 to 10 x 10 cm2). Using these p-i-n layers single junction solar cells & module were made.