Solution-produced copper iodide thin films for photosensor and for vertical thermoelectric nanogenerator, which uses a spontaneous temperature gradient

The article presents a new design of vertical thermoelectric nanogenerator (TENG) on the base of thin-film CuI/FTO composition with ohmic Cr/Cu contacts, which combines the functions of UV–Visible photosensor. Its functioning as the TENG carried out due to the spontaneous temperature gradient approximately 7 K, which occurs under the uniform heating of the entire device at temperature 30 °C. The open circuit voltage of TENG test sample is V_oc = 0.09 mV and maximum output power is P_max = 0.4 nW at temperature 50 °C. UV–Visible photosensor based on Cu/Cr/CuI/FTO/Cr/Cu composition possess high values of photocurrents I_ph under illumination, which eliminates necessity of amplification of the photosensor signal. The photoresponse and reset times of the photosensor are τ_p ≈ 30–100 s and τ_r ≈ 20–100 s, respectively. The explanation of the possibility of using CuI thin films, solution-produced by the affordable successive ionic layer adsorption and reaction (SILAR) method as both thermoelectric and photosensitive material is based on the studying of surface morphology, crystal structure, chemical composition and optical properties.