Photo-sensor characteristics of tannic acid (C76H52O46)/n-Si hybrid bio-photodiode for visible and UV lights detection

We present the electo-optical characterization of tannic acid (TA)/n-Si heterojunction for visible and UV lights (365 nm and 395 nm). The TA was deposited on n-Si by spin coating. The morphological and structural analyses of TA film were carried out by Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) analyses, respectively. The electro-optical performance of the TA/n-Si bio-photodiode were investigated by I-V measurements for 10 mW/cm(2), 15 mW/cm(2), 20 mW/cm(2) and 30 mW/cm(2) visible light intensities in addition to UV light. Light-dependent the responsivity, ON/OFF ratio, detectivity, shunt resistance and series resistance were calculated. Maximum values of responsivity, detectivity and ON/OFF ratio were determined as 11.9 mA/W (-1.5 V), 3.2 x 109 Jones (at-0.42 V) and 194 (30 mW/cm2) (AM 1.5 G), at-2 V respectively. Whereas, they were determined to be 0.1 A/W, 4 x 109 Jones and 14977, respectively for UV light. Furthermore, the dielectric properties of the TA/n-Si heterostructure also were investigated from the dark Capacitance/Conductance-Voltage measurements. It was seen that both real and imaginary parts of the dielectric constants was frequency dependent. Experimental results show that the TA/n-Si device with a high rectification ratio of 2263 is a potential candidate for detecting visible and UV lights.