Yes / Organic photovoltaics (OPVs) die due to their interactions with environmental gases, i.e., moisture and oxygen, the latter being the most dangerous, especially under illumination, due to the fact that most of the active layers used in OPVs are extremely sensitive to oxygen. In this work we demonstrate solution-based effective barrier coatings based on composite of poly(vinyl butyral) (PVB)and mica flakes for the protection of poly (3-hexylthiophene) (P3HT)-based organic solar cells (OSCs)against photobleaching under illumination conditions. In the first step we developed a protective layer with cost effective and environmentally friendly methods and optimized its properties in terms of transparency, barrier improvement factor, and bendability. The developed protective layer maintained a high transparency in the visible region and improved oxygen and moisture barrier quality by the factor of ~7. The resultant protective layers showed ultra-flexibility, as no significant degradation in protective characteristics were observed after 10 K bending cycles. In the second step, a PVB/mica composite layer was applied on top of the P3HT film and subjected to photo-degradation. The P3HT films coated with PVB/mica composite showed improved stability under constant light irradiation and exhibited a loss of <20% of the initial optical density over the period of 150 h. Finally, optimized barrier layers were used as encapsulation for organic solar cell (OSC) devices. The lifetime results confirmed that the stability of the OSCs was extended from few hours to over 240 h in a sun test (65◦C, ambient RH%) which corresponds to an enhanced lifetime by a factor of 9 compared to devices encapsulated with pristine PVB. / Higher Education Commission of Pakistan through NED University of Engineering and Technology, Karachi, Pakistan and “The APC was funded by Deanship of Scientific Research, King Saud University for funding through Vice Deanship of Scientific Research Chairs”.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2018-01-30T16:51:18Z No. of bitstreams: 2 Dissertação - Patricia de Almeida Machado Gonçalves - 2017.pdf: 2160802 bytes, checksum: 939d23474b7308d62b12f4b66224829d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-01-31T14:31:11Z (GMT) No. of bitstreams: 2 Dissertação - Patricia de Almeida Machado Gonçalves - 2017.pdf: 2160802 bytes, checksum: 939d23474b7308d62b12f4b66224829d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-01-31T14:31:11Z (GMT). No. of bitstreams: 2 Dissertação - Patricia de Almeida Machado Gonçalves - 2017.pdf: 2160802 bytes, checksum: 939d23474b7308d62b12f4b66224829d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-18 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Oxidative stress is the overproduction of reactive oxygen species that cause cell damage and even the death. It is a mechanism related to ischemia and reperfusion, a process that affects several organs and is involved in neurodegenerative diseases, cardiac and/or renal insufficiencies, hepatic dysfunction, among others. The discovery of new antioxidant substances derived from natural sources, is important for the prevention and treatment of these diseases. Beta lapachone is a substance with antioxidant action obtained from sawdust of Ipe wood, a symbolic tree from the Brazilian cerrado. This study aimed to analyze the cytotoxic and antioxidant action of beta lapachone in endothelial cells, in vitro. EA.hy 926 lineage cells were subcultured, treated with different concentrations of beta lapachone and subjected to ischemia and reperfusion. Cytotoxicity and antioxidant action were assessed through the cellular viability analysis by the tetrazolium reduction method. The averages were verified by the Tukey test (5% of significance) and by variance analysis. There was a dose-dependent progression of cytotoxicity in the non-ischemia/reperfusion (control) group and cell viability increase in the ischemia/reperfusion group. However, there was no statistical difference between the concentrations and between groups. Considering the settings of this experiment, Beta lapachone did not present cytotoxic or antioxidant action on endothelial cells. / O estresse oxidativo é o excesso de produção de espécies reativas de oxigênio que causam danos e até a morte das células. É um mecanismo que pode se originar da isquemia e reperfusão, um processo que acomete diversos órgãos e que está envolvido em doenças neurodegenerativas, cardíacas, insuficiências renais, disfunção hepática, entre outras. A necessidade da descoberta de novas substâncias antioxidantes, derivadas de fontes naturais, é importante para a prevenção e tratamento dessas doenças. A beta lapachona é uma substância com ação antioxidante, obtida da serragem da madeira do ipê, vegetação símbolo do cerrado brasileiro. Neste estudo objetivou-se analisar a ação citotóxica e antioxidante da beta lapachona em células endoteliais, in vitro. Células da linhagem EA.hy 926 foram subcultivadas, tratadas com a β lapachona em diferentes concentrações e submetidas à isquemia e reperfusão. A citotoxidade e a ação antioxidante foram obtidas por meio da análise da viabilidade celular pelo método de redução do tetrazólio. As médias foram averiguadas pelo teste de Tukey (5% de significância) e pela análise de variância. Houve progressão dose dependente da citotoxidade no grupo sem isquemia/reperfusão e da viabilidade celular no grupo com isquemia/reperfusão. No entanto, não houve diferença estatística entre as concentrações e entre os grupos. A beta lapachona, nas condições desse experimento, não apresentou ação citotóxica ou antioxidante nas células endoteliais.