Browsing by Author "Wolcan, E."

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    A tale of two organic small molecular hole transporting materials: Showing same extended shelf-life but very different efficiency of inverted MAPbI3 perovskite solar cells
    (Elsevier B.V., 2022) Kakekochi, V.; Kuo, D.-W.; Chen, C.-T.; Wolcan, E.; Chen, C.-T.; Udayakumar, U.K.
    This paper mainly discusses the structure-property relationship of two donor-acceptor-donor (D–π–A–π–D) type dopant-free hole transporting materials (HTMs) (TPA-TPy and TPA-Py-PTZ) comprising primarily of 2,4,6-trisubstituted pyridine as the acceptor core and 4,4′-dimethoxytriphenylamine as the peripheral donor groups and their use in p-i-n perovskite solar cells (PVSCs). Compared to inferior TPA-Py-PTZ, TPA-TPy has a superior hole extraction and hole transport at the HTM/perovskite interface. The pinhole-free, smooth and dense, fully covered and well-crystallized MAPbI3 perovskite layer on TPA-TPy reduces the carrier recombination and substantially improves the short circuit current density (JSC), open circuit voltage (VOC), and the fill-factor (FF) of MAPbI3 PVSCs. The PVSC employing TPA-TPy as HTM exhibits a power conversion efficiency (PCE) of 15.33% with a JSC of 23.69 mA cm−2, a VOC of 0.95 V, and a FF of 68.10%. Especially, both TPA-TPy and TPA-Py-PTZ PVSCs exhibit a better moisture stability than that of NiOx PVSCs. It is because of the hydrophobic nature of TPA-TPy and TPA-Py-PTZ, which enables the formation of MAPbI3 perovskite layer having a larger grain-size, a less grain boundary, and a less infiltration of moisture. © 2022 Elsevier B.V.
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    Facile synthesis and exploration of excited state assisted two-photon absorption properties of D-A-D type thiophene-pyridine derivatives
    (Royal Society of Chemistry, 2020) Kakekochi, V.; Chatnahalli Gangadharappa, S.; Nikhil, P.P.; Chandrasekharan, K.; Wolcan, E.; Udayakumar, U.K.
    A series of trigonal-shaped molecules (TPyT and TPyP) and a polymer (P2TPy) with donor-acceptor-donor (D-A-D) structural arrangement were designed with thiophene and 2,4,6-trisubstituted pyridine as the backbone i.e., a 4-(4-(decyloxy)phenyl)-2,6-di(thiophen-2-yl)pyridine core structure, for the first time and synthesized via a microwave assisted one pot reaction. The extension of conjugation of the system by substituting thiophene acrylonitrile (TPyT) and phenyl acrylonitriles (TPyP and P2TPy) via low cost condensation reactions improved the linear optical, electronic and thermal properties of the synthesized compounds. Furthermore, the nonlinear absorption (NLA) was also enriched appreciably by increasing the conjugation. The three compounds showed an "effective two-photon absorption" phenomenon with the NLA coefficient (?eff) of the order of 10-10 m W-1. The suitability to be utilized in the fabrication of all-optical limiting devices is best achieved by polymer P2TPy as it exhibits substantially higher ?eff (7.02 × 10-10 m W-1) and an extremely low optical limiting threshold (1.42 J cm-2). © 2020 The Royal Society of Chemistry and Owner Societies.