Sridharan Moorthy Babu

Study of the influence of dopants on the crystalline perfection of ferroelectric glycine phosphite single crystals using high-resolution X-ray diffraction analysis

Good quality and optically transparent single crystals of pure and doped glycine phosphite (GPI) were grown by both solvent-evaporation and temperature-cooling techniques. Dopants were chosen in different categories, namely transition metals (Cr, Mn, Co, Ni, Zn, Mg, Cd), rare-earth metals (Ce, Nd, La), dyes (rhodamine B, malachite green, fluorescein) and an amino acid (l-proline). The concentration of dopants was chosen depending on the category of dopants and the quality of crystallization during the growth process. The crystalline perfection of the as-grown pure and doped GPI crystals was investigated by high-resolution X-ray diffraction at room temperature. A multicrystal X-ray diffractometer employing a well collimated and highly monochromated Mo Kα1 beam and set in the (+, −, −, +) configuration was employed. Most of the crystal specimens show excellent crystalline perfection. However, grain boundaries, low-angle tilt boundaries, and vacancy and interstitial point defects were observed in some crystal specimens.

Formation of an interfacial MoSe2 layer in CVD grown CuGaSe2 based thin film solar cells

Thin polycrystalline films of CuGaSe 2 (CGSe) have been grown on Mo coated glass substrates by halogen supported chemical vapor deposition (CVD) with two different binary source materials, Cu 2 Se and Ga 2 Se 3 . Solar cells based on these absorber films prepared in a sequential two-stage process show efficiencies exceeding 6%. High resolution transmission electron microscopy investigation of the complete solar cell structure reveals a 170-nm thick MoSe 2 interfacial layer at the CGSe/Mo back contact. The crystallites of the MoSe 2 layered structure are found to be mainly oriented perpendicular to the Mo surface. The main focus of this investigation was to study the influence of the CVD process on the growth of MoSe 2 and the role the interfacial layer may have in the performance of the solar cell. For a detailed analysis we studied the growth and morphology of the interfacial layer dependent on the [Cu]/[Ga]-ratio in the gas phase during the CGSe deposition process and the Na content of the glass substrate. It was found that Na influences the growth of the MoSe 2 layer. By means of temperature dependent IV (IVT)-measurements the electrical properties of the CGSe/MoSe 2 /Mo heterostructure were investigated. In the heterostructure under investigation the MoSe 2 interfacial layer mediates an ohmic contact to the CGSe film.

Cesium lead halide ( CsPbX 3, X = Cl , Br, I) perovskite quantum dots-synthesis, properties, and applications: a review of their present status

Abstract. Metal halide-based perovskite quantum dots (QDs) have emerged as promising materials for optoelectronics and future energy applications. Among them, cesium lead halide-based perovskite quantum dots (Cs-LHQDs) have been found to be potential luminescent candidates and alternatives for the II–VI and I−III−VI2 groups semiconductor nanoparticles. These perovskites provide an excellent quantum yield (90%) larger than any other semiconductor QDs. At present, synthesis of Cs-LHQDs has been successfully achieved through a traditional colloidal-based hot-injection method and a room temperature precipitation method. Some of the interesting results in their structural, optical, and morphological properties are being analyzed to understand their energy-transfer mechanism in the colloidal state. Morphology of nanoplates, nanowires, nanocube, and nanosheets in these materials confirms their physical parameters-dependent self-assembly nature in a colloidal medium. Their potential use for light emitting diodes, photodetectors, and lasers is also highly motivated. This review provides a collective view of recent developments made in the synthesis of Cs-LHQDs and their properties.