Browsing by Subject "Degradation mechanism"

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    Classical modeling of extrinsic degradation in polycrystalline perovskite solar cells defect induced degradation
    (Elsevier BV * North-Holland, 2023-08-18) Mahiny, M.; Ahmadi-Kandjani, S.; Olyaeefar, Babak
    In the realm of photovoltaic devices, the future appears bright for polycrystalline perovskite solar cells. However, the promise of their efficiency is threatened by a myriad of degradation mechanisms. These mechanisms, like dark spots on a sunny day, create shadows of uncertainty on the performance of polycrystalline PSCs. Nonetheless, this article comprehensively explains these degradation mechanisms and their impact on grain boundaries in PSCs. The paper investigates grain boundaries’ effects on carrier lifetime by employing various models, such as the Matthiessen rule and the Drude–Smith method. The findings reveal that defect density is the primary factor affecting the material’s performance, and grain boundaries’ size influences its changes. Drude–Smith’s model provides a more precise estimation of the mobility, total scattering lifetime, and PL quantum yield in polycrystalline semiconductors with reduced scattering time. The presented method is verified by feeding extracted parameters into Drift-Diffusion equations and fitting them with reported experimental photovoltaic conversion efficiency data. Furthermore, based on the simulation results and the strong correlation between grain boundaries and the time factor, the study proposes a comprehensive model that can effectively predict PSCs’ degradation time.
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    Magnetic Properties and Environmental Temperature Effects on Battery Performance of Na0.67Mn0.5Fe0.5O2
    (Wiley-VCH Verlag GmbH & Co. KGaA, 2021-03-31) Altın, S.; Bayri, A.; Altın, E.; Öz, Erdinç; Yaşar, S.; Altundağ, S.; Harfouche, M.; Avcı, S.
    Herein, a modified solid state synthesis of Na0.67Mn0.5Fe0.5O2 and the results of a detailed investigation of the structural and magnetic properties via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis are reported. The magnetic properties of Na0.67Mn0.5Fe0.5O2 do not fit the Curie–Weiss law and a model regarding the spin configuration of the Mn and Fe ions and a possible ferrimagnetic order is suggested. Electrochemical measurements and ex situ structural analysis of the cathode material confirm the reversible structural transitions for the cells charged up to 4.0 V. Environmental temperature–dependent electrochemical measurements reveal a strong temperature dependence of both, the initial capacity and the capacity retention. Ex situ SEM, FTIR, and XRD studies on the battery membrane verify the formation of a Na2CO3 phase on the membrane, which blocks the Na ion diffusion through membrane pores and is responsible for the capacity fade for this compound.