Orange-red fluorescent polymer nanocomposite films with large stokes shift: An opto-electronic exercise

Abstract

Herein, we report the successful fabrication of orange-red fluorescent polymer nanocomposite (PNC) hybrids, that envisage efficient photon management and appreciable UVA-protection, besides high design flexibilities and ease of self-cleaning. The visibly transparent PNC thick films were developed via aqueous solution casting of -OH backboned poly (vinyl alcohol) (PVA) with nanostructured sodium zincate (Na2ZnO2). The as developed PNC films offer appreciable photonic down-conversion of high energy UVA-radiations to relatively lower energy Orange-red light via fluorescent emission. The optical band gap studies reveal a direct band gap relationship with valence band maxima and conduction band minima occurring at same wave vectors. While, static contact angle measurements support nanofiller induced wettability transitions (hydrophilic to near hydrophilic). The fluorescence spectral (excitation and emission) studies of PVA/Na2ZnO2 NC films validate a promisingly large Stokes shift (~245 nm), which visualises a fair separation between the photonic absorption and emission bands, that may further aid an exponential minimization of optical losses due to re-absorption. The thermogravimetric studies support their excellent thermal stabilities. The relatively large Stokes shift, appreciable thermal stability and excellent UV harvesting ability of PVA/Na2ZnO2NC films construct them as competent luminescent down-shifting (LDS) materials for possible solar cell applications.