Perspectives of chalcopyrite-based CIGSe thin-film solar cell: a review

Solar photovoltaic (PV) is empowering, reliable, and ecofriendly technology for harvesting energy which can be assessed from the fact that PV panels with total electricity generation capacity of 505 GW have been installed by the end of 2018. Thin-film solar cells based on copper indium gallium selenide (CIGSe) are promising photovoltaic absorber material owing to an alternative to crystalline silicon (c-Si)-based solar cells because of the huge potential for low-cost solar electricity production with minimal usage of raw materials. The efficiency record of 23.4% was achieved recently in CIGSe solar cells, which was comparable to c-Si solar cells (27.6%). The manufacturing cost of $0.34/W is expected for 15% efficient CIGSe module. The present review article discusses the perspectives of CISe/CIGSe-based thin-film solar cells with the focus on absorber material. Different vacuum and non-vacuum techniques for fabricating these materials are discussed along with the operation of solar cells and their manufacturability. The working mechanism of CIGSe solar cells with the characteristic features of the open-circuit voltage and current density as well as the factors influencing the efficiency in different fabrication techniques are reviewed. Moreover, some strategies toward the improvement of solar cells performance contemplating modified deposition are reviewed. Furthermore, how these strategies can be executed in order to make it cost effective methods is also discussed in detail. Prevailing constrictions for the commercial maturity are deliberated, and future perspectives for improvement at lab as well as industrial scalabilities are outlined

Impact of primary headaches on subjective sleep parameters among adolescents

Context: Headache patients commonly report sleep disruption and sleep disorders. Available literature suggests that the sleep pattern of headache sufferers is different from the control group. Patients in these studies were recruited from headache clinics; they did not include tension type headache. Aims: The aim of this study is to find out whether primary headaches affect sleep patterns. Settings and Design: Community based cross sectional study Materials and Methods: This study was conducted in three high schools. Children in the 12-19 age group were allowed to participate. They were given a questionnaire in the presence of at least one of the authors, who assisted them in filling it. They were asked to provide responses based on most severe recurrent headache that they had experienced rather than the more frequent ones. The questionnaire included questions regarding demographic data and the characteristics of headache according to International Classification of Headache Disorders-2 criteria. Part B of the questionnaire contained questions regarding sleep habits. The children were asked to provide data regarding sleep habits on a normal school day. Diagnosis was based upon the information contained in the questionnaire. A telephonic interview was also done, where the information provided was found inadequate. Statistical Analysis Used: Analysis was done with the help of SPSS v. 11.0., descriptive analysis, Chi square, and one way ANOVA with post hoc analysis. Kruskall-Wallis tests were run. Results: A total of 1862 subjects were included in the study. Migraineurs and tension type headache sufferers comprised 35.7% and 13.4% of the group respectively. Migraineurs had the highest prevalence of nocturnal awakenings ( P < 0.001), abnormal movements ( P =0.001) and breathing problems during sleep ( P < 0.001). Approximately half the migraineurs felt sleepy during the day ( P < 0.001) and spent around 1.17 hours in sleep during the day ( P = 0.007). Similarly, values for frequency of nocturnal awakenings per week ( P < 0.001), wake time after sleep onset and offset ( P < 0.001 and 0.002 respectively) were the maximum in migraineurs. Only 32.8% migraineurs reported refreshing sleep ( P < 0.001). Post hoc analysis revealed that migraineurs were different from the other two groups on most of the parameters. Conclusions: Sleep disruption is more common in migraineurs than those in the tension type headache sufferers and the control group