Photoresponse in the ultraviolet–visible–NIR range of octahedral MnCo2O4 microparticles synthesized by the solution method

The photodetection properties of MnCo2O4 were investigated in the ultraviolet (UV-A), visible, and near-infrared (NIR) range. The oxide was synthesized from manganese and cobalt chlorides using a nonaqueous solution method. Octahedral microcrystals with sizes between 1.8 and 6 µm were obtained at 700 °C, in air. The optical bandgap energy was calculated by the Tauc method giving 1.71 eV. Photocurrent results obtained with UV-A light (λ = 365 nm) show a fast response, with current changes from 6 to 120 µA for optical irradiances (Ee) between 10 and 100 mW/cm2. Polarization curves show a linear increase of photocurrent with voltage, indicating ohmic behavior. The effect of wavelength on the photocurrent was investigated using violet light, sunlight, and near-infrared radiation (NIR). The graphs revealed that, regardless of wavelength radiation, the photocurrent increases exponentially with Ee, because of electron–hole pair formation and radiation absorption. The general results suggest a promising use in the detection of UV–visible, but it has limitations for NIR radiation.