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    Structural and photoelectrical properties of an MDMO-PPV/n-Si hybrid heterojunction photodiode for broadband detection
    (Elsevier, 2026) Karaca, Abdullah; Yildiz, Dilber Esra; Hussaini, Ali Akbar; Yildirim, Murat; Gunduz, Bayram
    Organic-inorganic hybrid photodiodes are attractive for low-cost, broadband photodetection, yet the role of the polymer/Si interface on power-and wavelength-dependent performance is still not fully clarified. In this study, we fabricate a simple Al/MDMO-PPV/n-Si/Al heterojunction photodiode using a solution-processed MDMO-PPV interlayer and systematically correlate its structural, optical and electrical characteristics. UV-Vis spectroscopy reveals a pronounced absorption band at 478nm, and Tauc analysis yields a direct optical band gap of 2.28 eV. XRD and SEM measurements indicate a predominantly amorphous, porous polymer film with short-range order, providing interconnected pathways for charge transport. Current-voltage measurements under light illumination from 20 to 100 mWcm(-2) show clear rectification with negligible dark current. Thermionic-emission and Cheung analyses give ideality factors of 3.0-3.5 and zero-bias barrier heights of 0.69-0.74 eV, while the photocurrent follows a power law I-ph proportional to P-1.42, evidencing trap-assisted photoconduction. The device operates over 300-1050 nm, where the responsivity (R) increases from 0.15 to about 0.42 AW(-1), the photosensitivity (K) rises to approximate to 4 - 13, and the specific detectivity (D) improves from similar to 1.1 x 10(10) to similar to 1.8 x 10(10) Jones. Time-resolved measurements at 0V bias yield rise and fall times of 0.70 s and 0.94 s, respectively. These results demonstrate that an MDMO-PPV interlayer can efficiently extend n-Si photodiodes into the visible-NIR region and provide bias-free broadband detection, offering a scalable and low-cost platform for next-generation optoelectronic and sensing applications.
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    The light detection performance of Al/DPAVBi/n-Si heterojunction for wide-range spectrum
    (Elsevier Science Sa, 2025) Kocyigit, Adem; Hussaini, Ali Akbar; Yildiz, Dilber Esra; Gunduz, Bayram; Yildirim, Murat
    The 4,4 '-Bis[4-(di-p-tolylamino)styryl]biphenyl (DPAVBi) is a sky-blue fluorescent emitter and widely used in organic light emitting diodes (OLED) for improving optoelectronic behaviors. In this study, we employed DPAVBi as interfacial layer between Si and Al metal by spin coating technique to investigate its detection performance under various light power densities and across a broad spectrum from ultra-violet (UV) to near infrared (NIR). The crystallinity and surface morphology of DPAVBi layer were characterized by x-ray diffractometer (XRD) and scanning electron microscope (SEM). UV-Vis spectrometer was utilized to determine absorption behavior and band gap of DPAVBi layer. The diode and photodetector characteristics of the Al/DPAVBi/n-Si heterojunction were obtained by current voltage (I-V) and current-transient (I-t) measurements. According to thermionic emission theory, the Al/DPAVBi/n-Si heterojunction exhibited an ideality factor (n) of 4.07 and a barrier height (& Fcy;(b)) of 0.65 eV. The diode parameters were also confirmed by Cheung and Norde methods. The responsivity, photosensitivity, and specific detectivity values were also determined depending on the illumination of light power density and in the case wavelength. The Al/DPAVBi/n-Si heterojunction exhibited 0.89 A/W responsivity under sunlight. The wavelength-dependent photodetector parameters revealed that the Al/DPAVBi/n-Si heterojunction is more sensitive to light illumination in the visible region at a wavelength of 600 nm. The obtained results highlight that Al/DPAVBi/n-Si heterojunction can be employed as promising potential for optoelectronic applications in the visible range.
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    The light detection performance of Al/VNPB/n-Si Schottky photodetectors for a wide-range spectrum
    (Elsevier, 2026) Yildiz, Dilber Esra; Manfo, Theodore Azemtsop; Hussaini, Ali Akbar; Yildirim, Murat; Gunduz, Bayram
    A novel organic-inorganic Schottky photodetector incorporating a N4, N4 '-di(Naphthalen-1-yl)-N4, N4 '-bis(4-vinylphenyl)biphenyl-4,4 '-diamine (VNPB) thin film interlayer was fabricated and systematically characterized. The Al/VNPB/n-Si Schottky photodetectors were investigated using UV-Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), revealing strong visible light absorption and high crystallinity. Electrical measurements under varying illumination intensities demonstrated enhanced rectification and significant photocurrent generation, attributed to thermionic emission and efficient photocarrier formation. Under solar illumination (20-100 mW/cm(2)), the device demonstrated strong photocurrent generation, high photosensitivity (22.05-80.58), responsivity up to 2.18 A/W, and detectivity values on the order of 10(10) Jones, confirming efficient low-noise photodetection. The device exhibited high photosensitivity, responsivity, and specific detectivity across a broad spectral range (351-1600 nm), with peak performance at 600 nm, where a maximum responsivity of 0.0366 A/W, an external quantum efficiency of similar to 75%, and a detectivity of 6.11 x 10(9) Jones were achieved. In addition, strong near-infrared performance was observed at 1000 nm, with a photosensitivity of 4.85 and a detectivity of 5.76 x 10(9) Jones. Compared to oxide-based photodetectors, the Al/VNPB/n-Si architecture demonstrated superior optoelectronic performance, positioning VNPB as a promising interfacial material for next-generation photodetection technologies.
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    The light detection performance of the Al/DCJTB/n-Si Schottky type photodetector for a wide-range spectrum
    (Elsevier, 2026) Manfo, Theodore Azemtsop; Yildiz, Dilber Esra; Hussaini, Ali Akbar; Yildirim, Murat; Gunduz, Bayram
    The 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) is a red fluorescent dye known for its high luminescence efficiency, color purity, and resistance to concentration quenching. DCJTB was applied as an interfacial layer between Si and Al via spin coating to investigate its effect on Schottky photodetector performance at various light intensities and wavelengths (UV-Vis-NIR). Structural and optical properties of the DCJTB layer were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) spectroscopy. Current-voltage (I-V) and current-time (I-t) measurements revealed that the Al/DCJTB/n-Si heterojunction exhibits an ideality factor (n) of 3.15 and a barrier height (Phi b) of 0.701 eV under dark conditions. With increasing illumination (20-100 mW/cm2), n varied from 3.884 to 3.077, while the barrier height increased slightly. The device achieved a responsivity (R) of 0.63 A/W and a specific detectivity of 1.63 x 1010 Jones under sunlight. The external quantum efficiency (EQE) reached 0.68 % at 550 nm, confirming high sensitivity in the green region, while performance declined beyond 700 nm. These findings demonstrate that the Al/DCJTB/n-Si heterojunction is most effective in the visible spectrum, making it promising for optoelectronic and photodetection applications.