Fluorine-doped SnO2 thin films deposited on polymer substrate for flexible transparent electrodes

Abstract

Fluorine-doped SnO2 (FTO) thin films are deposited by ultrasonic spray pyrolysis on preheated polyimide (PI) substrates. Their structural, electro-optical and electro-mechanical properties are investigated versus both growth temperature and film thickness. FTO thin films exhibit textured columnar grain morphology and preferred orientations along the <101>, <301>, <211> and <200> are favored depending on growth temperature and film thickness. The films deposited on PI substrate at 380°C present the best compromise in terms of electro-optical properties with a low electrical resistivity of 8.9×10−4Ωcm, a mobility of 17.9cm2/V·s combined with an optical transmittance up to 79.4% at 780nm. Eventually, a figure of merit of 2.3×10−3Ω−1 is obtained. The electro-mechanical properties are studied during controlled fatigue testing and analyzed according to the energy-based Griffith's criterion.