A. Dere

Ruthenium(II) Complex Based Photodiode for Organic Electronic Applications

In this study, the electrical and photoresponse properties of a photovoltaic device with Ruthenium(II) complex interfacial thin film were investigated. Heteroleptic Ru(II) complex including bidentate and tridentate ligands thin film was coated on n-Si substrate by the spin coating technique. From current–voltage (I–V) measurements of an Au/Ru(II)/n-Si photodiode, it is observed that the reverse bias current under light is higher than that of the current in the dark. This indicates that the photodiode exhibits a photoconducting characteristic. The transient measurements such as photocurrent, photocapacitance and photoconductance were performed under various illumination conditions. These measurements indicate that the photodiode has a high photoresponsivity. The electrical parameters such as barrier height (Φb), ideality factor (n) and series resistance (Rs) of the photodiode were determined from the analysis of I–V characteristics. Moreover, the capacitance/conductance–voltage characteristics of the photodiode highly depend on both voltage and frequency. Results show that the heterojunction can be used for various optoelectronic applications.

Structural, electrical and photoresponse properties of si-based diode with organic interfacial layer containing novel cyclotriphosphazene compound

The electrical and photoresponse properties of Al/p-Si/organic layer/Al diode were investigated. Organic layer containing novel 2,2-bis[spiro(7,8-dioxy- 4-methylcoumarin)]-4,4,6,6-bis[spiro(2’,2”-dioxy-1’,1”- biphenylyl)]cyclotriphosphazene compound was coated by drop casting method on p-Si having ohmic contact. The structural characterization of novel cyclotriphosphazene compound was confirmed by using 1H, 13C and 31P-NMR, elemental analysis and FT-IR spectroscopic techniques. The diode exhibits a photoconducting and photodiode behavior under solar light illumination. The electrical parameters such as ideality factor, barrier height and series resistance of the diode were determined from I-V characteristics. It is seen that the photocurrent of the diode under illumination is higher than dark current. Also, the frequency dependence of capacitance (C) and conductance (G) was explained on the basis of interface states. It is evaluated that the hybrid photodiode can be used as a photosensor in organic photodetector applications.

Synthesis, photophysical, DFT and photodiode properties of subphthalocyanine–BODIPY dyads

In this study, subphthalocyanine–borondipyrromethene conjugates have been successfully designed and synthesized. The novel compounds were fully characterized by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and 1H and 13C NMR spectroscopies. The photophysical properties of the conjugates were investigated by means of absorption and fluorescence spectroscopies in benzene solutions. The results showed that while the absorption spectra of both conjugates remain almost the same, compound 5 has a better fluorescence behavior and higher energy transfer efficiency. To test the effect of the replacement of the methyl group in the conjugates, Density functional theory (DFT) was used to calculate the equilibrium geometries of the ground state for the conjugates. The torsional angle of the BODIPY with reference to Sub-Pc in compound 5 (−125.4°) was different than that in compound 6 (−91.4°). This planarization results in a decrease in the orbital energy of the BODIPY unit in compound 5, making a smaller gap for the energy transfer mechanism between the BODIPY and Sub-Pc unit. In addition, their photodiode properties were tested here. The obtained phototransient current and capacitance results indicated that the devices exhibit both photodiode and photocapacitor properties. Therefore, it can be concluded that the subphthalocyanine–borondipyrromethene conjugate-based photodevices can be used as photodiodes in solar tracking systems.

Investigating the coumarin capability in chalcogenide 20TI 2 Se–80Pr 2 Se 3 system based photovoltaics

Chalcogenide films containing various contents of coumarin (CO) are deposited on the p-type Si substrates. Al/coumarin doped chalcogenide films/p-Si contact exhibits a rectifying behavior. The electrical and photoresponse properties of the prepared diodes are characterized by current and capacitance measurements under various illumination intensities. The addition of coumarin to TI2Se-Pr2Se3 significantly affects the characteristic parameters of diodes. Kohlrausch function is used as an appropriate way to obtain the photo charge density (ρph) and the relaxation time constant from the photocurrent/capacitance transients. It is shown that coumarin doped chalcogenide films have a potential to obtain the photocarrier generation.

Cadmium Oxide:Titanium Dioxide Composite Based Photosensitive Diode

Cadmium oxide:titanium dioxide (CdO:TiO2) composite thin films with various ratios of CdO contents were prepared on p-type silicon semiconductor substrates by the sol–gel spin coating method. Al/CdO:TiO2/p-Si/Al heterojunction devices exhibited optoelectronic device behavior due to their photocurrent under solar light illuminations. The photoresponse behavior of the diodes is controlled by changing the molar ratio of CdO to TiO2. The fabricated CdO:TiO2 (2:1) based device exhibited the highest photoresponse of about 7.5 × 103. The interface properties of the devices are changed with the molar ratio of CdO:TiO2. The obtained results suggest that CdO:TiO2 composite film/p-type Si structure can be used in optoelectronic applications.

Organic Semiconductor: Graphene-Oxide/p-Si Photodiodes

The device parameters of Al/p-Si/PCBM:GO/Au diodes were investigated using direct current–voltage (I–V ), photocurrent and impedance spectroscopy. The ideality factor of the diode was found to depend significantly on GO content. The calculated barrier heights had low variance over the range of illumination intensities per doping level. Under dark conditions the barrier height averaged 0.767 with a variance of less than 40 parts per million and the ideality factors averaged 10.2± 0.4, both parameters taken across all the varying GO contents. The high ideality factors (>9) of the heterostructure organic/inorganic diodes are explained in terms of the low carrier mobilities of the organic interlayer. Capacitance–voltage measurements indicate that the capacitance decreases with increasing frequency, suggesting a continuous distribution of interface states over the surveyed 100 kHz to 1.0 MHz frequency range. The photocurrent results indicate that the photocurrent increases with illumination intensity. The Al/p-Si/PCBM:GO/Au diode exhibits a similar photosensitivity with an illumination coefficient of approximately 1.23± 0.001 over a wider range of PCBM:GO weight ratios and reverse bias. This suggests that the device photoconductivity is reasonably predictable and particularly suited for photoconductive sensing.