Solar Cells: In Research and Applications—A Review

The light from the Sun is a non-vanishing renewable source of energy which is free from environmental pollution and noise. It can easily compensate the energy drawn from the non-renewable sources of energy such as fossil fuels and petroleum deposits inside the earth. The fabrication of solar cells has passed through a large number of improvement steps from one generation to another. Silicon based solar cells were the first generation solar cells grown on Si wafers, mainly single crystals. Further development to thin films, dye sensitized solar cells and organic solar cells enhanced the cell efficiency. The development is basically hindered by the cost and efficiency. In order to choose the right solar cell for a specific geographic location, we are required to understand fundamental mechanisms and functions of several solar technologies that are widely studied. In this article, we have reviewed a progressive development in the solar cell research from one generation to other, and discussed about their future trends and aspects. The article also tries to emphasize the various practices and methods to promote the benefits of solar energy.

Clinical pregnancy rate of women with unexplained infertility with or without cervical mucus aspiration before intrauterine insemination: A randomized controlled trial

Objective:To detect effect of removing cervical mucus before performing intrauterine insemination(IUI)on pregnancy rate in patients with unexplained infertility.Methods:The randomized controlled trial was conducted in Infertility Division of Department of Obstetrics and Gynaecology of a tertiary care hospital.Totally 80 patients of unexplained infertility were recruited.By computer generated block randomization in block size of 4 and 6,patients were randomly allocated at time of starting ovarian stimulation into the cervical mucus removal group or the non-removal of cervical mucus group before IUI,40 in each group.Ovarian stimulation with clomiphene 100 mg from day 2-6 of menstrual cycle along with human menopausal gonadotropin 150 IU was given alternate day starting from day 7.Follicular monitoring was done and further doses given as per response;trigger was planned when 1-3 follicle reach a diameter of>18 mm.IUI was planned after trigger.IUI was done as per the group allocated.Mucus cleaning was done in the cervical mucus removal group by aspirating mucus with IUI syringe and sterile cotton swab before IUI.The primary outcome was clinical pregnancy rate.Number of difficult IUIs and cycle cancellation due to ovarian hyperstimulation were also noted.Results:IUI was not done in 4 patients due to hyperstimulation.Pregnancies per IUI cycle occurred in 7.9%(3/38)in the cervical mucus removal group and 21.1%(8/38)in the non-removal of cervical mucus group.There was no statistically significant difference in clinical pregnancy rate between two groups(P=0.19).Conclusions:There is a trend towards a lower clinical pregnancy rate with removal of cervical mucus before IUI in women of unexplained infertility though the difference is not statistically significant.Further studies with large sample size need to be done on this intervention.

Theoretical Investigations on the π-π Stacking Interactions in Phenol-Water Complexes

Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well established and account well for the experimental long range interaction energies for small clusters of aromatic molecules and most of the calculations were carried out using the MPn methods. If a reasonably large basis set is used to calculate the stacking interaction energies for a cluster (dimer, trimer etc.) of aromatic molecules then the electron-electron correlation energy may be properly calculated. Moreover, ab initio calculations for aromatic π-systems show that the calculated stacking interaction energies highly depend on the basis set used and the electron correlation energy. In this investigation, the electron correlation of the stacked hydrated phenol systems has been accounted at MP2 level of calculations. We have calculated the π-π stacking interaction energies of the hydrated phenolic systems with different conformations.

Quantum Mechanical Studies on the Mode of Hydrogen Bonding, Stability and Molecular Conformations of Phenol-Water Complexes

It is experimentally well established that the phenolic systems such as phenol and diphenols undergo strong hydrogen bonding interaction with water molecule. But, the possible mode hydrogen bonding in phenol-water systems may be of different types. Although, the experimental methods are not always well enough to give the proper hydrogen bonding conformations in the phenol-water complexes. The hydrogen bonding ability in phenol-water systems can directly be influenced by changing the interacting sites in the given molecular systems, which could be investigated by theoretical studies. Generally, in phenol-water system, the hydrogen bonding is taking place through −OH group of phenol with water molecule, and this kind of interactions between phenol-water and diphenol-water complexes have been extensively investigated in electronic ground state by Quantum Mechanical MP4 calculations. It is also very important to study the stability of different phenol-water complexes and to find out the proper phenol-water complexes with minimized interaction energy. This study will also be helpful for understanding the effect of hydrogen bonding interaction in a better way on other aromatic systems.

Quantum Mechanical Study on the π-π Stacking Interaction and Change in Conformation of Phenolic Systems with Different Intermolecular Rotations

Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces;ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.