Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Bildiri & Sunum Koleksiyonu
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Öğe Organic ammonium halide modulators as effective strategy for enhanced perovskite photovoltaic performance(John Wiley and Sons Inc, 2021) Akın, Seçkin; Dong, B.; Pfeifer, L.; Liu, Y.; Graetzel, M.; Hagfeldt, ADespite rapid improvements in efficiency, long-term stability remains a challenge limiting the future up-scaling of perovskite solar cells (PSCs). Although several approaches have been developed to improve the stability of PSCs, applying ammonium passivation materials in bilayer configuration PSCs has drawn intensive research interest due to the potential of simultaneously improving long-term stability and boosting power conversion efficiency (PCE). This review focuses on the recent advances of improving n-i-p PSCs photovoltaic performance by employing ammonium halide-based molecular modulators. The first section briefly summarizes the challenges of perovskite materials by introducing the degradation mechanisms associated with the hygroscopic nature and ion migration issues. Then, recent reports regarding the roles of overlayers formed from ammonium-based passivation agents are discussed on the basis of ligand and halide effects. This includes both the formation of 2D perovskite films as well as purely organic passivating layers. Finally, the last section provides future perspectives on the use of organic ammonium halides within bilayer-architecture PSCs to improve the photovoltaic performances. Overall, this review provides a roadmap on current demands and future research directions of molecular modulators to address the critical limitations of PSCs, to mitigate the major barriers on the pathway toward future up-scaling applications.Öğe Metal oxide electron transport materials for perovskite solar cells: a review(Springer Science and Business Media Deutschland GmbH, 2021) Valadi, Kobra; Taheri-Ledari, Reza; Akın, Seçkin; Maleki, Ali; Shalan, Ahmed EsmailSolar electricity is an unlimited source of sustainable fuels, yet the efficiency of solar cells is limited. The efficiency of perovskite solar cells improved from 3.9% to reach 25.5% in just a few years. Perovskite solar cells are actually viewed as promising by comparison with dye-sensitized solar cells, organic solar cells, and the traditional solar cells made of silicon, GaAs, copper indium gallium selenide (CIGS), and CdTe. Here, we review bare and doped metal oxide electron transport layers in the perovskite solar cells. Charge transfer layers have been found essential to control the performance of perovskite solar cells by tuning carrier extraction, transportation, and recombination. Both electron and hole transport layers should be used for charge separation and transport. TiO2 and 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene are considered as the best electron and hole transport layers. Metal oxide materials, either bare or doped with different metals, are stable, cheap, and effective.Öğe Comparison of MgAl2Si2O8:Mn4+ Systems Doped with Co-Activator Ions in Terms of Long Lifetime for Optoelectronic Applications(IEEE, 2014) Öztürk, Esra Çırçır; Kalaycıoğlu, Nilgün ÖzpozanMn-4 doped and Pr-3+,Pr-4, Sm-3, Gd-3, Tb-3+,Tb-4, Ho3+, Er3+, Tm-3 and Yb3+ co-doped MgAl2Si2O8-based phosphors were prepared by conventional solid state synthesis at 1300 degrees C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600-715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic E-2 ->(4)A(2) transitions of Mn-4.
