Browsing by Author "Tok, Mutahire"

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Citation - WoS: 3
Citation - Scopus: 2
Dual- and Triple- Hetero-Atom Carbon Dots as Novel Additives for the Engineering of Defects Passivation To Boost Performance of Perovskite Solar Cells
(Springer, 2025) Kurukavak, Cisem Kirbiyik; Tok, Mutahire; Yurdakul, Merve; Kus, Mahmut
Methylammonium lead iodide (MAPbI3)-based perovskite solar cells (PSCs) offer highly efficient photovoltaics. However, several disadvantages such as poor stability and possibility of defect formation reducing film quality have restricted its commercialization. In this work, we reported the synthesis of dual- and triple-hetero-atom-doped carbon quantum dots (CQDs) via hydrothermal method and their effect of use as additive on the performance of PSCs. The boron (B) and phosphorous (P)-doped CQDs (B,P-CQDs), sulphur (S) and P-doped CQDs (S,P-CQDs), and B, S, and P-doped CQDs (B,S,P-CQDs) additives were described. Since these CQDs have many functional groups including hydroxyl (-OH), they can easily interact with Pb ions leading to the formation of PbO, as well as interaction with methyl ammonium ions. A reduced halide vacancy density and an increased nucleation energy of perovskite enhance crystal sizes and charge transfer. The passivation of surface defects reduces non-radiative recombination and ion migration, which plays an important role in photodegradation of the MAPbI3 films. Herein, the introduction of S,P-CQDs improved power conversion efficiency (PCE) from 10 to 15% and current density (Jsc) from 14.4 to 23.6 mA cm-2. PSCs added with dual- and triple-hetero-atom-doped CQDs showed narrower efficiency distribution in comparison to the control devices.
Citation - WoS: 3
Citation - Scopus: 2
Effect of Hetero-Atom Doping on the Structure and Optical Properties of Carbon Quantum Dots for the Sensitive Detection of Heavy Metal Ions
(Wiley, 2025) Kurukavak, Cisem Kirbiyik; Tok, Mutahire; Toprak, Aysegul; Yurdakul, Merve; Ersoz, Mustafa
Metal pollution in water sources due to modernization is a human health and environmental problem. Therefore, the highly fluorescent boron- and nitrogen-doped and nitrogen-doped carbon quantum dots (B,N-CQDs and N-CQDs, respectively) were synthesized and investigated to be used as a fluorescence sensor for metal ion detection. In this study, the synthesized B,N-CQDs and N-CQDs had an average size of 4-6 nm and 3-4 nm, respectively. The B,N-CQDs presented high sensitivity as 0.0090, 0.0086 and 0.0091 units per micromolar for Cr3+, Cu2+ and Fe2+, respectively, whereas the N-CQDs showed sensitivity as 0.0047, 0.0102, 0.0095 and 0.0121 units per micromolar for Cr3+, Cu2+, Fe2+ and Ni2+, respectively. In the concentration range of 10-80 mu M, the detection limits of B,N-CQDs and N-CQDs were found to be in the range of 13.9-65.5 mu g/L and 14.9-38.3 mu g/L, respectively. The result of the study clearly indicates that B,N-CQDs and N-CQDs can be seen as metal ion sensing devices with high sensitivity and low cost.
Ligand-Dependent Performance Optimization of CsPbX3/N-Si Schottky Photodiodes for Broadband Photodetection
(Springer, 2025) Varal, Nurhan Mehmet; Tok, Mutahire; Kirbiyik Kurukavak, Cisem; Durmus, Haziret; Kus, Mahmut
All-inorganic cesium lead halide perovskite nanoparticles (CsPbX3, X = Cl, Br) are promising candidates for optoelectronic devices due to their high absorption coefficients, narrow emission linewidths, and superior thermal stability compared to hybrid perovskites. In this work, Schottky photodiodes were fabricated on n-type Si substrates using CsPbBr3 and CsPbCl3 nanoparticle interlayers, both with native oleylamine/oleic acid ligands and after pyridine-based ligand exchange. Structural and morphological analyses via AFM revealed that pyridine treatment improved surface uniformity for CsPbBr3 films but induced aggregation in CsPbCl3 films. Electrical characterization using thermionic emission theory, Cheung's method, and Norde's method showed composition- and ligand-dependent variations in barrier height, series resistance, and ideality factors. Under varying illumination intensities, pyridine-treated CsPbBr3 devices (D2) exhibited over tenfold improvements in responsivity and detectivity compared to their untreated counterparts (D1), while pyridine-treated CsPbCl3 devices (D4) demonstrated high performance at low light intensities and maintained strong broadband detection from 351-1600 nm. CsPbCl3 devices with native ligands (D3) displayed unstable performance, excelling only in the long-wavelength infrared region (> 1400 nm). These results highlight the critical role of surface chemistry in tailoring perovskite-silicon photodiodes for broadband photodetection applications.
Citation - WoS: 18
Citation - Scopus: 19
Phosphorus Doped Carbon Dots Additive Improves the Performance of Perovskite Solar Cells Via Defect Passivation in Mapbi3 Films
(Elsevier, 2023) Kırbıyık Kurukavak, Çisem; Yılmaz, Tuğbahan; Büyükbekar, Alihan; Tok, Mutahire; Kuş, Mahmut
Perovskites have been widely investigated as absorber layer in photovoltaic technology owing to their excellent properties. For further enhancement of the power conversion efficiencies (PCEs) of MAPbI3 perovskite solar cells, here, we successfully synthesized phosphorus doped carbon dots (P-CQDs) by solvothermal method and inves-tigated their effect as an additive on the perovskite film properties and photovoltaic performance. The results showed that electron-rich phosphorus can act as an excellent core unit in perovskite absorber layer to passivate defects at the surface for improved the crystallization and charge transport properties. Thanks to passivation effect of P-CQDs on perovskite films, as well as the suitable energy band gap values and optical properties of MAPbI3 layer, the device prepared with the addition of 5 vol% of P-CQDs achieved a champion PCE of 13.12% with a high fill factor (FF) of 73.44%, higher than the PCE of 10.71% with a FF of 58.81% for control device.
Citation - WoS: 7
Citation - Scopus: 7
Substitution Effects in Distyryl Bodipys for Near Infrared Organic Photovoltaics
(Elsevier Science Sa, 2022) Tok, Mutahire; Say, Büşra; Dölek, Gamze; Tatar, Beytullah; Özgür, Derya Öncel; Kurukavak, Çisem Kırbıyık; Çakmak, Yusuf; Kuş, Mahmut
In this research, four new conjugated Bodipy (boron dipyrromethene) structures absorbing in the near IR region have been synthesized and their photophysical, electrochemical, morphological properties and their potential for organic photovoltaics (OPV) have been investigated. All the compounds were substituted with bithiophene units in their 3-and 5-positions. Besides, the meso (8-) and 2-, 6-positions were substituted with different groups, and it allowed analysis of substitution effects in these positions on the performance of organic photovoltaics. Among the synthesized compounds, BTT has better photovoltaic performance than others with 1.3% power conversion efficiency (PCE) value when an organic solar cell with PC71BM acceptor compound was formed under the optimized conditions. Experimental and theoretical studies demonstrated that photovoltaic performance is largely affected by the units on the meso position under the compounds studied and the electronic distributions of the frontier molecular orbitals which are presumably dictated by the orientation of the side groups around the Bodipy core. We believe, with the light of the studies performed novel substitution transformations would enhance implementation of these types of compounds in near infrared photovoltaics.
Citation - Scopus: 1
Use of Cspbx3 Nanocrystals as an Additive in Organic Solar Cell for Efficiency Improvement
(Elsevier, 2025) Kurukavak, Cisem Kirbiyik; Tok, Mutahire
Here, we aimed to investigate the dependence of organic solar cells (OSCs) performance on the CsPbX3 perovskites nanocrystals (PNCs). The effect of presence of CsPbX3 (X = Cl, Br, and I) NCs in photoactive layer was studied using various characterization techniques. UV-Vis spectroscopy and XRD patterns of P3HT:PCBM thin films showed that the light harvesting, crystallinity and phase separation increased by the introducing PNCs, which improved the electrical properties. The AFM images supported the improved crystallinity of P3HT and homogeneous structure of photoactive layer. OSCs with the configuration of ITO/PEDOT:PSS/P3HT: PCBM: PNCs/LiF/Al were fabricated. The PNCs incorporation resulted to efficiency enhancement from 1.75 % to 2.88 % (P3HT:PCBM - CsPbBr3). The increase in efficiency was strongly related to the improved current density (J(sc)) (10.75 mA cm(- 2)) and open-circuit voltage (V-oc) (0.598 V).