Mohammad Azad Malik

Routes to tin chalcogenide materials as thin films or nanoparticles: a potentially important class of semiconductor for sustainable solar energy conversion

Thin films of tin chalcogenides may find use in photovoltaic devices, and nanocrystals of such materials are attractive due to their tuneable band gaps and potential in photovoltaic, photonic and optoelectronic applications. Tin(II) sulfide (SnS) is of particular interest due to its band gap of 1.4 eV, which is similar to that of silicon (1.1 eV). This review seeks to provide an overview of the chemical routes currently known for the synthesis of tin chalcogenides as thin films or in nanocrystalline form, as well as exploring routes to copper zinc tin sulfide (CZTS) and mesoporous tin chalcogenides.

Transition metal doped pyrite (FeS2) thin films: structural properties and evaluation of optical band gap energies

Iron pyrite (FeS2) is a semiconductor comprised of earth-abundant elements and has the potential to be a low cost photovoltaic material with comparatively low toxicity. The properties of transition metal doped iron pyrite thin films (MxFe1−xS2 where M = Co, Ni, Cu, or Zn) deposited by aerosol-assisted chemical vapour deposition (AACVD) on various substrates including glass, (100) silicon and indium tin oxide (ITO) have been studied. Changes in the cubic lattice parameter as well as peak broadening on doping were observed by powder X-ray diffraction (p-XRD) measurements. The structural properties of the transition metal doped pyrite (MxFe1−xS2) depend strongly on the transition metal dopant used and preferred orientation in all films was found to be along the (200) plane. The influence of transition metal doping on the structure and phase transformation was significant in copper doped pyrite thin films. The height-profiling of MxFe1−xS2 films with atomic force microscopy (AFM) displayed smooth surfaces with uniform distribution of particles. Optical studies revealed that there is increment in the bandgap of MxFe1−xS2 thin films which is supported by previous work. There may be contribution from oxidation of the doped pyrite surface in band gap enhancement observed by X-ray photoelectron spectroscopy (XPS). These findings may be important to improve doped pyrite layers for photovoltaic devices.

Bis(selenobenzoato)dibutyltin(IV) as a single source precursor for the synthesis of SnSe nanosheets and their photo-electrochemical study for water splitting

A new organo-tin complex has been synthesized and used as a single source precursor for the synthesis of SnSe nanosheets by the hot injection method and thin films by the aerosol assisted chemical vapor deposition (AACVD) method. The films were deposited on glass substrates at three different temperatures. The textural quality and preferential growth were found to be significantly altered by changes in the deposition temperature. Oleylamine capped nanosheets and the as-deposited thin films by AACVD were characterized by powder X-ray diffraction (p-XRD) and microscopic techniques. The thin films were also studied by Raman spectroscopy. The stoichiometry is marginally affected by temperature, and all films were slightly selenium deficient. The synthesized material was also evaluated for the photoelectrochemical (PEC) splitting of water. The PEC study revealed the bifunctional nature of the material, which can be applied for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), by switching the applied potential.