Browsing by Author "Cevher, D."
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Item Open Access Boosting the efficiency of organic solar cells via plasmonic gold nanoparticles and thiol functionalized conjugated polymer(Elsevier, 2022-11) Karakurt, O.; Alemdar, E.; Cevher, D.; Gulmez, S.; Taylan, Umut; Cevher, S. C.; Hizalan Ozsoy, G.; Ortac, Bulend; Cirpan, A.Conjugated polymers are promising low-cost, lightweight, and flexible candidates for scalable photovoltaic applications to establish decarbonized energy technologies. However, they possess deficiencies in terms of their lower charge mobility and exciton diffusion length compared to their inorganic counterparts, impeding the efficient charge extraction at high active layer thickness values. In this manner, active layer composition should be tuned to improve light harvesting enabling efficient charge transport. This work presents two new approaches to achieve higher photovoltaic performance for organic photovoltaic systems; thiol modification of the polymers for improved morphological features, and incorporation of ligand-free gold nanoparticles with surface plasmon absorption into the active layer to be stabilized by the covalent interaction with the thiol side groups of the polymers. To achieve this goal, a benzoxadiazole bearing polymer (POxT) and its bromine (POxT-Br) and thiol (POxT-SH) comprising derivatives were synthesized, their electrochemical, optical, photovoltaic, and morphological characterizations were performed. For photovoltaic characterizations, conventional device architecture of ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al was utilized, where the POxT-SH showed the highest JSC and PCE values, 6.52 mA/cm2 and 2.71%, respectively. Gold nanoparticles were synthesized via laser ablation method, and upon incorporation, the PCE value was boosted to 3.29%, with an increase of 21.4% compared to POxT-SH comprising organic solar cells.Item Open Access Experimental and ab-initio investigation of the electrical conductivity of emeraldine salt(American Chemical Society, 2023-03-31) Ergönenç Yavas, Z.; Cevher, D.; Silis, H. T.; Cirpan, A.; Gülseren, Oğuz; Franchini, C.We present an experimental and first-principles study to describe the changes in the electrical conductivity properties of the Emeraldine Salt (ES) form of polyaniline when using two different synthesis methods. The ES powders obtained by the interfacial synthesis method (PANI-I) exhibit higher electrical conductivity than that of the powders obtained by the conventional method (PANI-C). Investigation of the calculated band structure and density of states together with experimentally obtained optical-absorption spectra and the magnetic measurements indicate that PANI-I differs from PANI-C with respect to its localized defect state type which significantly alters the intrinsic conductivity. Furthermore, comparative studies of bond length, dihedral angles, and relative stabilities of Leucomeraldine Base, Emeraldine Base, ES Bipolaron state (ESB), and Polaron state (ESP) indicate that ESB and ESP states might coexist. Additionally, we confirm that increasing the length of the polymer chain to octamer in the unit cell does not influence the relative stability between ESB and ESP defect states.