There is a large social need for renewable energy in the country especially solar energy. With about 300 clear, sunny days in a year, India’s theoretically calculated solar energy incidence on its land area alone is about 5,000 trillion kilowatt-hours (kWh) per year (or 5 EWh/yr). The development of next generation, high efficiency and stable solar cells will enable us to provide power in remote areas of the country and therefore will have a large social and technological impact. The recent emergence of efficient solar cells based on organic/inorganic lead halide perovskite absorbers promises to transform the fields of dye-sensitized, organic, and thin film solar cells.
Photophysics Study in Perovskite Solar Cells:
Our achievement is the fabrication of all air processed and stable perovskite solar cells upto 15% efficiency and we have studied their detailed morphology optimization and photophysics. We have designed and reported a novel method of controlling surface roughness in perovskite solar cells named dual solvent elimination method which leads to larger grain size and better crystallinity at room temperature. We achieved much higher crystallinity and uniformity in lead and lead free perovskite film by solvent annealing method.
Large Area and Stable Perovskite Solar Cells:
Metal halide perovskites attract considerable attention for application in photovoltaic cells. We focus on the development of large area, high efficiency and stable perovskite solar cells involving various device engineering protocols for morphology optimization and scalable manufacturing of air-stable solar cells. We study charge carrier dynamics by various techniques like transient absorption spectroscopy, transient PL spectroscopy, confocal microscopy, temperature dependent photo luminescence spectroscopy, impedance spectroscopy and c-AFM.
Carrier Dynamics in Two-Dimensional Perovskite:
Two-dimensional (2D) Ruddlesden–Popper perovskite materials gained importance due to its higher photo stability, when compared to its three-dimensional (3D) counterpart. In our group, we study the exciton binding energy, charge carrier recombination, charge carrier transport, and conductivity as a function of different organic and inorganic spacer cations chain length in these 2D quantum wells. We probe the fundamental photophysics in these 2D perovskite by different advanced spectroscopic techniques like transient spectroscopy and terahertz spectroscopy.
Perovskite Single Crystal:
Perovskite single-crystal, which exhibit exceptionally low trap density and nearly perfect transnational symmetry, are believed to achieve the highest performance of perovskite-based optoelectronic devices. Here, fabricate several lead free perovskite single crystals for photodetector and X-Ray detector application. We also study their charge carrier dynamics by temperature dependent photo luminescence spectroscopy, femtosecond transient absorption and photo luminescence spectroscopy, impedance spectroscopy, and electron spin resonance spectroscopy.
Singlet exciton fission-sensitized solar cells have the potential to exceed the Shockley-Queisser limit by generating additional photocurrent from high-energy photons. Here, our group will try to understand the underlying photophysics behind singlet fission in molecular systems and nanoparticles on sub 100s timescale.
Organic Nanoparticles based Solar Cells:
We have fabricated nanoparticles of donor polymers (low bandgap polymers like PTB7 and PCPPDT) and fullerene acceptor molecules (like PCBM) by applying mini-emulsion techniques in the presence of various cationic and anionic surfactants and studied their morphology and photophysics. Mobility of these nanoparticles was measured and these nanoparticles with opposite charges were self-assembled to control exciton diffusion length. In addition to studying photophysics and morphology, we demonstrated that the self-assembly of oppositely charged nanoparticles is a promising approach to design efficient bulk heterojunction.
Dye Sensitized Solar Cells:
We use different novel dyes as sensitizers and novel engineered carbon nanomaterials as counter electrode in DSSC. Recently, we fabricated DSSCs with four naturally occurring anthocyanin dyes extracted from naturally found fruits/juices (viz., Indian jamun, plum, black currant, and berries) as sensitizers.
 “Effect of size and charge asymmetry on aggregation kinetics of oppositely charged nanoparticles”, Kulveer Singh, Anubhav Raghav, Prateek K Jha, Soumitra Satapathi, Just Accepted, Nature Scientific Reports, 9 (1), 3762, 2019.
 “Charge Carrier Dynamics Study and Morphology Optimization in Solvent Annealed CH3NH3PbI3 Perovskite for Air Processed Stable Solar Cell Application”, Anubhav Raghav, Shivam Singh, Dhanashree Moghe, Shailendra Sharma, Dinesh Kabra, Soumitra Satapathi, Chemical Physics, https://doi.orgmphys/10.1016/j.che.2019.110408, 2019.
 “Morphological and photophysical study in hybrid ternary organic nanoparticles blends”, Anubhav Raghav, Mrinmoy K Chini, Amar Bheemaraju, Rajashik Paul, Soumitra Satapathi, Chemical Physics, 525, 110388, 2019.
 “Temperature Assisted Nucleation and Growth to Optimize Perovskite Morphology at Liquid Interface: A Study by Electrochemical Impedance Spectroscopy”, Priya Srivastava, Anukul Prasad Parhi, R Ranjan, Soumitra Satapathi, Monojit Bag, ACS Applied Energy Materials, 4420–4425, 1, 9, 2018.
 “Local optoelectronic characterization of solvent annealed lead-free bismuth-based perovskite films”, Jill Wenderott, Anubhav Raghav, Max Shtein, Peter Green, Soumitra Satapathi, , Langmuir, 7647-7654, 34, 26, 2018.
 “Controllable Bulk Heterojunction Morphology by Self-Assembly of Oppositely Charged Nanoparticles”,Kulveer Singh, Prateek K. Jha, and Soumitra Satapathi, Journal of Physical Chemistry C, 121, 16045−16050, 2017.
“Controlling morphology of CH3NH3PbI3 perovskite film by dual solvent elimination method”, Anubhav Raghav, Shivam Singh, Shailendra Kumar Sharma, Kabra Dinesh, Monojit Bag, Soumitra Satapathi, Nano-Structures & Nano-Objects, 12, 106–112, 2017.
 “Synthesis of Nanoparticles of P3HT and PCBM for Optimizing Morphology in Polymeric Solar Cells”, Soumitra Satapathi, Hardeep Singh Gill, Lian Li, Lynne Samukeson, Jayant Kumar,* Ravi Mosurkal, Applied Surface Science, 323, 3–18, 2014.
 “Photophysical Study of P3HT/NDI Based Hybrid Nanoparticles”, Soumitra Satapathi, Mijanur Rahaman Molla, Santanu Bhattacharya, Suhrit Ghosh and Amitava Patra, European Journal of Physics D, , 2014, 68:350, 2014.
 “Effect of functional groups on sensitization of dye-sensitized solar cells (DSSCs) using free base Porphyrins”, Nivedita Choudhary, Nipun Sahwney, Anubhav Raghav, M. Sankar, Soumitra Satapathi, Journal of Porphyrins and Phthalocyanines, 21, 222, 2017.
 “Utilization of Naturally Occurring Dyes as Sensitizers in Dye Sensitized Solar Cells.” Nipun Sawhney, Soumitra Satapathi, IEEE Photovoltaics, 7, 2, 539-544, 2017. [Featured in Nature Asia, PTI, Quartz, BBC, Chemical Today].