Dr. Sanchita Sengupta
Associate Professor, Chemical Sciences

Research Focus

Conversion of sunlight into useful forms of energy through photovoltaics is one of the most viable and attractive alternative to address the global concerns of energy supply. In this respect, development of new organic materials for organic photovoltaics (OPV) as well as (opto)electronic applications has been an important and rapidly emerging area of research.

Among the many classes of light harvesting (LH) materials,  Π -conjugated organic small molecules, dyes and pigments have garnered great attention with regard to their high absorption cross-section, facile optical and redox tunability, synthetic versatility, high charge carrier mobilities, low-cost and the possibility of their roll-to-roll processibility. Along these lines, research in our group will be aimed at developing new LH systems based on Π -conjugated molecules/dyes for (opto)electronic applications along the following themes:

1. Donor-acceptor (D-A) systems (in configurations such as D-A-D, A-D-A, D-A-A etc.) for efficient photoinduced electron transfer (PET). Major emphasis will be given on their photophysics, charge carrier mobilities and electronic properties in order to assess their suitability in photoconduction for OPV devices.

2. Covalently connected multichromophoric systems (based on squaraine, DPP, rylenes, BODIPY, isoindigo and few other classes of molecules with complementary absorption) with the aim of achieving efficient Förster resonance energy transfer (FRET). Design strategies would involve the use of dendritic structures where different chromophores can be positioned with favorable orientations for FRET. Eventual aim would be to achieve enhanced OPV performances compared to conventional donor-acceptor blends.

3. Covalently connected D-A systems with variable spacer unit(s) will be designed for twisted intramolecular charge transfer (TICT), aggregate induced emission (AIE) and/or thermally activated delayed fluorescence (TADF). Fundamental structure-property relationships of these materials will be deduced through structural and optical characterization. Eventually, the application of some of the screened materials in fabrication of organic light emitting diodes (OLEDs) will be explored.

4. FRET and PET properties will be tuned based on DFT computed optical properties of separate donor (energy/electron) and acceptor (energy/electron) units and this will form the basis for the synthesis of new LH materials. In order to understand the dynamics of various photophysical processes, ultrafast spectroscopic studies would be performed in collaboration.

Research in our group will involve extensive organic synthesis and structural characterization of new molecules/materials. Furthermore, the work will involve theoretical DFT and TD-DFT calculations, cyclic voltammetry, optical spectroscopy such as UV/Vis, fluorescence, emission lifetimes, fluorescence anisotropy, temperature dependence and internal quantum efficiency (IQE) measurements.

Selected Publications

• K. Rani, U. K. Pandey, S. Sengupta* Efficient Electron Transporting and Panchromatic Absorbing FRET Cassettes Based on Aza-BODIPY and Perylenediimide Towards Multiple Metal FRET-Off Sensing and Ratiometric Temperature Sensing. J. Mater. Chem. C, 2021, 9, 4607 - 4618 (https://doi.org/10.1039/D1TC00068C).
  
• Z. Wei, S. Sharma, A. M. Phillip, S. Sengupta, F. C. Grozema Excited State Dynamics of BODIPY-based Acceptor-Donor-Acceptor Systems: A Combined Experimental and Computational Study. Phys. Chem. Chem. Phys. 2021, 23, 8900-8907 (https://doi.org/10.1039/D1CP00453K).
  
• S. Sharma, Z. Wei, F. C. Grozema, S. Sengupta* Structure Property Relationship in Multi-Stimuli Responsive BODIPY-biphenyl-Benzodithiophene TICT Rigidochromic Rotors Exhibiting (Pseudo) Stokes Shift up to 221 nm. Phys. Chem. Chem. Phys. 2020, 22, 25514-25521 (https://doi.org/10.1039/D0CP04579A).
  (Featured in 2020 PCCP Hot articles).
  
• Aswathy P. R., S. Sharma, N. P. Tripathi, S. Sengupta* Regioisomeric BODIPY-Benzodithiophene Dyads and Triads with Tunable Red Emission as Ratiometric Temperature and Viscosity Sensors. Chem.-Eur. J. 2019, 25, 14870-14880 (https://doi.org/10.1002/chem.201902952).
  (Selected as Chem. Eur. J. Hot Paper)