Low field room temperature magnetism and band gap modifications in Sm doped SnO2

The structural, optical and magnetic properties of pure and Sm doped SnO2 nanoparticles synthesized in aqueous solution by a low cost chemical co-precipitation method without using any stabilizing agent have been reported. X-ray diffraction analysis reveals that the crystallite size of SnO2 decreases with the increase of Sm doping into the SnO2 matrix. The calculated value of optical band gap of undoped SnO2 nanoparticles is calculated to be 2.65 eV and it anomalously increases with the increase of Sm3+ concentration. The band gap of undoped SnO2 nanoparticles is found to be lower than those reported for bulk SnO2 (3.6 eV) that may be due to the presence of defects, oxygen vacancies and non-stoichiometry of SnO2 nanoparticles. All the undoped and Sm doped SnO2 nanoparticles show weak room temperature magnetism in the range of applied low magnetic field region of 2000 Oe due to the presence of defects and oxygen vacancies. All the samples exhibit negative magnetic susceptibility for the applied magnetic field higher than 2000 Oe. The strong optical absorption with weak magnetic properties at room temperature may serve the SnO2 nanomaterials as a potential candidate for many DMS, spintronics, and optoelectronics based applications

Effect of Mn doping on structural, optical and magnetic properties of SnO2 nanoparticles

The Mn doped SnO2 nanoparticles synthesized by cost effective chemical co-precipitation method has been investigated in the present work. The main focus of the work is to explore the structural, optical and magnetic properties of the SnO2 nanostructures. The crystallite size decreases with increase in Mn doping to SnO2 matrix. The optical band gap of doped SnO2 nanoparticles continuously decreases with increasing Mn ion doping concentration. All the doped SnO2 nanoparticles show paramagnetic behavior at room temperature. SnO2 exhibits ferromagnetic behavior in the range of low external applied magnetic field due to the presence of oxygen vacancies (V (o) (+) ) and defects. The undoped SnO2 nanoparticles are spherical in shape while Mn doped SnO2 nanoparticles show the segregation of the spherically shaped nanoparticles. Mn ions only enhance the paramagnetic ordering and degrade the ferromagnetism already present in the SnO2 nanoparticle

Basic concepts, engineering, and advances in dye-sensitized solar cells

The day–by-day increasing need for light energy has reduced the necessary supply of energy for mankind usage and hiked the prices of natural energy resources. To avoid energy tragedy in future, one needs to use the non-degrading sources of energy for energy harvesting. The advancement in solar cell technology allows us to convert the sunlight more efficiently into electrical energy, though the low cost with highly stable and efficient solar cells is still desirable. The dye-sensitized solar cells (DSSCs), a class of third-generation photovoltaic cell, have emerged out as economic, eco-friendly, and much easier fabrication process over other existing technologies such as single-crystal Si solar cells, polycrystalline Si solar cells, thin-film solar cells, and other semiconductor (GaAs, CdTe, CuInSe2, etc.) thin films. The main challenge and limiting factor with DSSC’s fabrication are their efficiency and durability in the environment. In the last decade, enormous efforts have been made to improve the efficiency and stability of DSSCs. One of the possible ways is the manipulation of light at nanoscale on some metal–dielectric interface and integrating it on some cheaper electronic devices for highly efficient solar cell applications. On the other hand, the research on modifying the design and fabrication of photoanode, dyes materials, and counter electrode materials have paid huge attention in architecting DSSCs. This chapter provides an insight into the fabrication of DSSCs and the challenges associated with its fabrication, stability, and efficiency.Instituto de Física (IF