Exploring the radiant impact of irradiance on the electrical resistance of organic thin film

Abstract

This article reports on the light sensitivity of Organic Thin Film Transistors (OTFTs) based on Nickel Phthalocyanine (NiPc). Phototransistors with three distinct channel lengths (25 μm, 40 μm, and 50 μm) are fabricated and compared for performance analysis. We investigate the impact of irradiance at various frequencies under different applied voltages on the performance of the phototransistor. Light exposure influences the resistance of nickel-phthalocyanine. The resistance of nickel-phthalocyanine undergoes a decrement, ranging from 185 to 0.8 KΩ, as the incident light intensity increases from zero to 130 foot candela (f_c), while varying the frequency from 0.1 to 5 KHz. Under conditions of low frequency (100 Hz) and a channel length of 25 μm, the resistance of the fabricated photosensitive transistor exhibits a decrease from 92 to 40 KΩ during a voltage sweep of 5 V. The resistance of the organic phototransistor (OPT) is noted to decrease with rising irradiance, and its performance is superior at low frequencies compared to high frequencies. The decrease in resistance is attributed to the bound charge carriers that get sufficient energy from the absorbed photon to surmount the barrier when the incident light on the device possesses enough energy. These liberated conduction electrons, or holes left behind, move freely, resulting in lower resistance. The obtained results demonstrate the potential efficiency of organic photosensitive transistors for utilization in optoelectronic devices.