Negative photoconductivity: optical and structural characterization of PVP encapsulated CuO nanorods for the study of negative photoconductivity effect

In this report, the optical and structural properties of the PVP incorporated CuO naorods (NRs) have been studied and discussed for the observation of the photoconductivity response. The band gap of the CuO NRs was found to be & AP; 3.85 eV with UV and visible emission (violet and blue light) properties related to the defects and interstitial formation in the NRs. The observed quantum yield of blue higher emission around 487 nm is stronger than other emitted colors from the CuO NRs. Optical refractive index, susceptibility, and optical dielectric constant, conductivity, optical dispersion parameters have been studied from optical spectrum.The crystal phase from the XRD result showed a monoclinic nature with an average crystal size & AP;12.5 nm, strain & AP;0.002 and lattice parameters: a = 4.5578 & ANGS;, b = 3.5474 & ANGS;, c = 5.2911 & ANGS;. Formation of the pure phase of CuO and presence of different vibrational bond (such as the Cu-O stretching vibration along the [101] direction at 604.5 cm(-1)) have been observed from FTIR spectrum. The current-voltage characteristics of the polymer encapsulated CuO NRs deposited on the glass substance have been investigated after exposure to UV light. The maximum current under dark and UV illumination were 4 & mu;A and 0.075 & mu; A at 2 V, respectively. The carrier relaxation under UV irradiation showed negative photoconductivity (NPC) response with different relaxation time. The photoconductivity rise and decay showed the raise time t(1) = 1193 s, t(2) = 1050 s and decay time & tau;(1) = 935 s, & tau;(2) = 188 s. The decay current under UV light showed the involvement of carrier relaxation by the trapping process as well as recombination process. The carrier dynamics and NPC study in the PVP encapsulated CuO NRs is useful for the future optoelectronic devices.

Automated summary

This study investigates the optical and structural properties of PVP incorporated CuO nanorods (NRs) for photoconductivity response. The CuO NRs exhibit a band gap of approximately 3.85 eV with UV and visible emission properties related to defects and interstitial formation. Optical refractive index, susceptibility, dielectric constant, conductivity, and dispersion parameters were studied from the optical spectrum. XRD analysis reveals a monoclinic crystal phase with an average crystal size of around 12.5 nm and lattice parameters of a = 4.5578 ANGS, b = 3.5474 ANGS, c = 5.2911 ANGS. FTIR spectrum confirms the formation of pure CuO phase and presence of vibrational bonds. The current-voltage characteristics of the encapsulated CuO NRs show a negative photoconductivity (NPC) response under UV illumination with different relaxation times. The carrier dynamics and NPC study of PVP encapsulated CuO NRs have implications for future optoelectronic devices.