Low voltage driven P3HT/PS phototransistor for ultra-high power efficiency UV sensing

Abstract

This study explores the physical properties and electrical characteristics of a regioregular poly 3-hexylthiophene (rr-P3HT) semiconductor blended with the polymer insulator polystyrene. Given the high operating voltage required by conventional P3HT transistors, we employed a hybrid dielectric layer, combining plasma-reacted metal oxide with a polymer pre-layer (AlO_x/PMMA and HfO_x/PMMA), to reduce the operating voltage of P3HT transistors. As a result, an operating voltage lower than −5 V for the blended sample was achieved. The structural, morphological, and electrical properties of the prepared blended sample were investigated using XRD, AFM, XPS, UV–Visible spectroscopy, Raman spectroscopy, and I–V characteristics. The blended sample exhibits improved crystalline ordering and an extended effective conjugation length, accompanied by an increased formation of dendritic P3HT fibrils that enhance UV absorption. PS captures generated electrons, effectively delaying their recombination with generated holes in P3HT. This leads to heightened UV responsivity in P3HT/PS transistors. The key discovery of this study is the ultra-low power consumption UV sensing device. The blended sample, illuminated with a UV intensity of 550 μW/cm², exhibited the highest sensitivity of 194.5, nearly 60 times higher than that of pristine P3HT. Consequently, our investigated device shows promise for applications in visible-blind sunlight or environmental monitoring systems, given its ultra-high-power efficiency.