Fabrication of non-fullerene P3HT/Agx-TiO2 based polymer solar cells with high open circuit voltage

Abstract

Abstract This paper describes the effect of localized surface plasmon resonance (LSPR) in the non-fullerene bulk heterojunction polymer solar cells (BHJ PSCs) by incorporating Ag x -TiO 2 nanocomposites into the active layer. Four types of Ag x -TiO 2 nanocomposites with different contents of Ag and distinctly different crystallite size and great uniformity were synthesized to systematically probe their influences on photovoltaic performances of PSCs. The nanocomposites were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and diffuse reflectance spectroscopy (DRS) and were compared with the corresponding data of pure TiO 2 . The crystallite size of Ag x -TiO 2 decreased as the Ag content of the nanocomposites increased. The effect of Ag x -TiO 2 on the chemical and optical properties of P3HT was studied using UV–Vis spectroscopy, photoluminescence (PL) spectroscopy and cyclic voltammetry (CV) technique. The electron-hole recombination rate and also the band gap of P3HT were significantly decreased in combination with Ag x -TiO 2 . I–V characteristics of PSC devices improved significantly as the Ag content of the Ag x -TiO 2 nanocomposites increased. The best devices were found to have an open circuit voltage (V OC ) of about 1 V and power conversion efficiency (PCE) of about three times higher than that obtained for TiO 2 -based devices, prepared at the same conditions. PCE of these devices was however about 28% lower than that of PCBM-based PSC devices fabricated in this work. The current study shed light on how plasmonic nanostructures of Ag x -TiO 2 influences light absorption, exciton generation, exciton dissociation and charge transport inside non-fullerene based PSC devices.