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    Exploring the relationship between reaction temperature and photodetection properties in Sb2Se3 thin film-based devices
    (Elsevier, 2025) Olgar, Mehmet Ali; Yilmaz, Salih; Rehman, Fazal; Bacaksiz, Emin
    This paper focuses on optimizing the reaction temperature of Sb2Se3 thin films for photodetector applications. The films were grown using a two-stage method on glass substrates. Structural analysis revealed the formation of the orthorhombic Sb2Se3 phase along the (020) plane, and increasing the reaction temperature up to 400 degrees C improved the crystal quality. Notably, the most promising structural properties were achieved for Sb2Se3 thin films reacted at 380 degrees C. Raman spectra confirmed the presence of tetragonal and amorphous selenium, along with Sb2Se3. Morphological analysis showed that a horizontally aligned rod morphology developed as the Sb2Se3 thin film grew, with the rod sizes increasing as the reaction temperature reached to 400 degrees C. X-ray photoelectron spectroscopy (XPS) revealed the formation of Sb-Se and Sb-O bonds, along with the presence of unreacted oxygen atoms near the surface of Sb2Se3 thin films reacted at 340 degrees C. Photoluminescence data indicated a bandgap value of 1.24 eV for Sb2Se3 films reacted at 380 degrees C. The current-voltage (I-V) curves exhibited a linear dependence for all Sb2Se3-based devices, suggesting ohmic contact between the films and the electrodes. The fastest photo- response was observed for the photodetector annealed at 380 degrees C, with rise and fall times of 26 ms and 40 ms, respectively. Additionally, the highest responsivity (R = 8.0 x 10-4 A/W), detectivity (D* = 3.8 x 106 Jones), and external quantum efficiency (EQE = 16.3%) were achieved by the same device, indicating that the optimal reaction temperature for Sb2Se3 thin films and their photodetector applications is approximately at 380 degrees C.
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    Unveiling improvements in structural, optical, and photodetection characteristics of CZTS thin films through Ag-doping
    (Elsevier, 2025) Rehman, Fazal; Yilmaz, Salih; Polat, Ismail; Bacaksiz, Emin; Zan, Recep; Olgar, Mehmet Ali
    The study investigated the characterization of photodetectors made from CZTS (Cu2ZnSnS4) thin films by introducing silver (Ag) as a dopant. CZTS thin films were grown on Mo-foil by two stage process, comprising sputter deposition of metallic precursor layers followed by sulfurization process employing Rapid Thermal Annealing (RTA) approach. The stacking order for the undoped and Ag-doped CZTS thin films were Substrate/ ZnS/Cu/Sn/Cu and Substrate/ZnS/Cu/Sn/Cu/Ag, respectively. Photodetectors (PDs) were fabricated using sputter deposition on glass, including CZTS, Ag-doped CZTS-5 (8 nm Ag), Ag-doped CZTS-10 (16 nm Ag), and Agdoped CZTS-15 (24 nm Ag). Various characterization methods were utilized to examine the prepared thin films, including Energy Dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), optical transmission, Photoluminescence (PL) and photodetection analyses. Among all devices, Ag-CZTS-10 PDs exhibited the best performance, showing a crystallite size (D) of 51.72 nm, band gap of 1.47 eV and favorable SEM surface morphology. For the photodetection characteristics, blue light at 443 nm and red light at 525 nm wavelength were used with an applied bias of 2V, and a light intensity of 17.3 mW/cm2. The highest responsivity (R) values recorded for Ag-CZTS-10-based PDs were 0.0024 A/W for blue and 0.0019 A/ W for red light. Additionally, the detectivity (D*) was 3.4 x 106 Jones for blue and 2.3 x 106 Jones for red light, while sensitivity (S) was 26 % for blue and 15 % for red light. This study successfully demonstrated, for the first time, the fabrication of low-cost, high-performance Ag-doped CZTS films-based PDs on glass substrates which hold promise for the development of cost-effective and efficient optoelectronic devices.