Yazar "Shalan, Ahmed Esmail" seçeneğine göre listele

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    Composition engineering of operationally stable CsPbI2Br perovskite solar cells with a record efficiency over 17%
    (Elsevier, 2021) Öztürk, Teoman; Akman, Erdi; Shalan, Ahmed Esmail; Akın, Seçkin
    Despite the rapid progress in inorganic cesium lead halide perovskite (CsPbX3) materials originating from excellent thermal stability; their poor phase stability at room temperature and lower efficiency compared to organic-inorganic counterparts still limit their development toward commercialization. Recently, Pb-site doping of inorganic perovskites stand outs for the improvement of aforementioned issues for emerging photovoltaic applications. Herein, we introduce a compositional engineering approach to tune the CsPbI2Br crystallization by directly incorporating iron (II) chloride (FeCl2) into perovskite precursor. The small amount of FeCl2 stabilizes the black α-phase to avoid the undesirable formation of the non-perovskite phase owing to Fe2+ induced grain size reduction. Besides, the FeCl2 incorporation thoroughly align the energy level, promote the built-in potential (Vbi), and reduce the defect states in the perovskite, resulting in a record power conversion efficiency (PCE) of 17.1% with a remarkable open-circuit voltage (VOC) of 1.31 V. More importantly, FeCl2-doped CsPbI2Br-based devices exhibit an exceptional operational stability with a retention of over 95% initial PCE after 330 h at maximum power point (MPP) tracking.
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    Efficient and stable perovskite solar cells enabled by dicarboxylic acid-supported perovskite crystallization
    (2021) Shalan, Ahmed Esmail; Akman, Erdi; Sadegh, Sadegh; Akın, Seçkin
    Defect states at surfaces and grain boundaries as well as poor anchoring of perovskite grains hinder the charge transport ability by acting as nonradiative recombination centers, thus resulting in undesirable phenomena such as low efficiency, poor stability, and hysteresis in perovskite solar cells (PSCs). Herein, a linear dicarboxylic acid-based passivation molecule, namely, glutaric acid (GA), is introduced by a facile antisolvent additive engineering (AAE) strategy to concurrently improve the efficiency and long-term stability of the ensuing PSCs. Thanks to the two-sided carboxyl (-COOH) groups, the strong interactions between GA and under-coordinated Pb sites induce the crystal growth, improve the electronic properties, and minimize the charge recombination. Ultimately, champion-stabilized efficiency approaching 22% is achieved with negligible hysteresis for GA-assisted devices. In addition to the enhanced moisture stability of the devices, considerable operational stability is achieved after 2400 h of aging under continuous illumination at maximum power point (MPP) tracking.
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    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 Esmail
    Solar 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.
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    Moisture-resistant FAPbI(3) perovskite solar cell with 22.25 % power conversion efficiency through pentafluorobenzyl phosphonic acid passivation
    (Wiley, 2021) Akman, Erdi; Shalan, Ahmed Esmail; Sadegh, Faranak; Akın, Seçkin
    Perovskite solar cells (PSCs) have shown great promise for photovoltaic applications, owing to their low-cost assembly, exceptional performance, and low-temperature solution processing. However, the advancement of PSCs towards commercialization requires improvements in efficiency and long-term stability. The surface and grain boundaries of perovskite layer, as well as interfaces, are critical factors in determining the performance of the assembled cells. Defects, which are mainly located at perovskite surfaces, can trigger hysteresis, carrier recombination, and degradation, which diminish the power conversion efficiencies (PCEs) of the resultant cells. This study concerns the stabilization of the alpha-FAPbI(3) perovskite phase without negatively affecting the spectral features by using 2,3,4,5,6-pentafluorobenzyl phosphonic acid (PFBPA) as a passivation agent. Accordingly, high-quality PSCs are attained with an improved PCE of 22.25 % and respectable cell parameters compared to the pristine cells without the passivation layer. The thin PFBPA passivation layer effectively protects the perovskite layer from moisture, resulting in better long-term stability for unsealed PSCs, which maintain >90 % of the original efficiency under different humidity levels (40-75 %) after 600 h. PFBPA passivation is found to have a considerable impact in obtaining high-quality and stable FAPbI(3) films to benefit both the efficiency and the stability of PSCs.
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    Neodymium and praseodymium doped perovskite materials for highly stable CuInS2-hole-transport layer-based perovskite solar cells
    (John Wiley and Sons Inc, 2021) Taheri-Ledari, Reza; Gharibi, Saideh; Maleki, Ali; Akın, Seçkin; Shalan, Ahmed Esmail
    Organic–inorganic hybrid perovskite (PSK) technology is a new class of solar cells which have attracted great attention due to the rapid progress in photovoltaic performance and ease of processing pathways. Herein, a novel method for the enhancement of the photovoltaic and photoelectric properties of the triple-cation Cs/MA/FA PSK layer is presented. For this purpose, two lanthanide ions, including praseodymium (Pr3+) and neodymium (Nd3+), are prepared in nanoscale and incorporated into the PSK structure as B-site dopants, which results in an improved crystallinity, prolonged charge-recombination process, and increased light harvesting while yielding higher efficiency. Moreover, inorganic copper indium sulfide (CuInS2) hole-transport layer is used instead of the high cost and organic spiro-OMeTAD to reduce production costs and enhance the device stability of PSK photovoltaics. Ultimately, a notable efficiency of 15.75% with a significant short-circuit current density of 24.54 mA cm−2 is achieved by the utilization of PSK + Pr layer in a large-scale (1.4 × 1.4 cm2) perovskite solar cell. More importantly, the devices maintain 94.3% of their initial performance for 10 day/night cycles under ambient conditions.