Structural, optical and junction characteristics of pyrazolo pyridine derivatives

Abstract

Two pyridine derivatives, 6-(2-chlorophenyl)-2,3-dihydro-1-methyl-3-oxo-2-phenyl-1H-pyrazolo[4,3-b]pyridine-5-carbonitrile (C1) and 6-(4-chlorophenyl)-2,3-dihydro-1-methyl-3-oxo-2-phenyl-1H-pyrazolo[4,3-b] pyridine-5-carbonitrile (C2) are prepared and characterized. Different techniques were applied to confirm their molecular structures. The thermal, structural, optical and diode characteristics of the two pyridine derivatives are reported. X-ray diffraction (XRD) patterns of C1 and C2 in powder form reveal monoclinic polycrystalline nature. The optical functions of C1 and C2 films are calculated from the transmittance and reflectance spectra measured over the spectral range 200–2500 nm. Two indirect allowed optical energy gaps were estimated; 2.55 and 3.13 eV for C1 and 2.7 and 3.27 eV for C2. Thin films of the two compounds were deposited onto p-Si substrates for fabricating heterojunctions. The diode ideality factor and barrier height of both devices were calculated. In addition, Norde's function was used to determine the important parameters of the devices. At relatively high voltage, the conduction mechanism is described by space charge limited current in both devices. The conduction of the device based on C1 and C2 compounds are due to pool–Frenkel and Schottky mechanisms. The data at reverse biasing are also analyzed and estimated. The device based on C1 compound did not give any response to light, while that based on C2 can used as photosensor.