• M SENTHILKUMAR

Articles written in Bulletin of Materials Science

• Ligand exchange in Cu$_2$ZnSnS$_4$ nanoparticles and its effect on counter electrode performance in dye-sensitized solar cells

Ligand-exchanged Cu$_2$ZnSnS$_4$ (CZTS) nanoparticles (NPs) were successfully synthesized from colloidal NPs by replacing the long chain organic ligand from the surface of NPs via a bi-phasic method. It was found that ammonium sulphide salt ((NH$_4$)$_2$S) plays a key role in changing the surface of the NPs from hydrophobic to hydrophilic. The efficacy of the ligand exchange process over the surface of the CZTS NPs was analysed using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and scanning electron microscopy with energy dispersive X-ray. The ligand-exchanged CZTS NP-based counter electrodes (CEs) were fabricated by drop casting the inorganic ligand (ammonium sulphide)-capped CZTS nanoink onto the conducting substrate. Our result indicates that dye-sensitized solar cells (DSSCs) with inexpensive CZTS NP-based CEs show 2.42% efficiency. The present result indicates that CZTS CEs will be helpful as an alternative CE to a Pt CE in DSSC application.

• A modified high-temperature vapour deposition technique for fabricating CH$_3$NH$_3$PbI$_3$ thin films under an ambient atmosphere

A modified two-step deposition technique was performed by vapour depositing methylammonium iodide (MAI) on lead iodide (PbI$_2$) films to fabricate good quality methylammonium lead iodide (MAPI) thin films under anambient atmosphere, and their properties were compared with conventional two-step solution processed MAPI thin films. Scanning electron microscopy results depicted that the MAI vapour-processed films have a uniform coverage and planar surface compared with the non-uniformly distributed granule-like morphology of the solution-processed MAPI film. X-ray diffraction results confirm that the vapour-processed films have better crystallinity compared to the conventional solutionprocessed MAPI thin films. An enhancement in the optical absorption and emission was observed for the vapour-processed films. The higher processing temperature of the modified-vapour deposition eliminates the effect of moisture during the ambient atmosphere processing of the MAPI films.

• Copper indium sulphide:zinc sulphide (CIS:ZnS)-alloyed quantum dots as an eco-friendly absorber in solar cells

Synthesis and characterization of less toxic copper indium zinc sulphide (CIS:ZnS)-alloyed quantum dots (QDs) were carried out and the ligand exchange process towards the efficiency enhancement in CIS:ZnS QD-sensitized solar cellwas demonstrated. The colloidal CIS:ZnS QDs were synthesized by an inexpensive heat up method with oleic acid as the capping ligand. The optical properties were analysed through ultraviolet–visible absorption and photoluminescence emission spectroscopy. The influence of the ligand exchange process on the CIS:ZnS QD-based solar cells was analysed with thefabrication of two batches of solar cells. The ligand exchange process was confirmed from Fourier transform infrared and thermogravimetric analyses. The QD-sensitized solar cells were fabricated using a CIS:ZnS QD-loaded titania photoanode and by employing copper sulphide as the counter electrode. The photovoltaic performance of the fabricated QD solar cells was analysed through photovoltaic characterization methods (current density–voltage characteristics of the devices under the simulated solar light conditions and external quantum efficiency measurements). The ligand-exchanged QD-loaded solar cells show enhanced power conversion efficiency compared to the long chain ligand-capped CIS:ZnS QD-sensitized solar cells.

• Synthesis and characterization of L-threonine ammonium bromide: grown on single crystal with experimental studies on NLO

L-threonine ammonium bromide (LTAB) is a significant nonlinear optical (NLO) material. The crystal has been grown by the slow evaporation technique (SET). Ammonium bromide has properties, which are that of chiral molecules and zwitterions environmental benefits due to advance NLO properties of LTAB. L-threonine-doped ammonium bromide crystals are grown using SET at ambient temperature. In this study, the unit cell factors are derived from X-ray diffraction (XRD) studies. The powder XRD spectra suggests the formation of orthorhombic crystal system. Fourier transform infrared spectroscopy (FTIR) analysis depicts the different functional groups offered in the grown crystals. The study of optical transmittance was done by crystals utilizing ultraviolet, visible, spectral analytical methods. Further, the minimum cutoff wavelength of the grown crystal has been recognized as 220 nm. The overall result of the second harmonic generation (SHG) efficiency is depicted higher and nearly around LTAB obtained crystal which is greater than potassium dihydrogen phosphate (KDP). It proves the potential application of LTAB crystal in optoelectronic industries.

• # Bulletin of Materials Science

Volume 44, 2021
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020