Electro-photovoltaics of grignard metathesis-derived poly(propylene imine) tetra(salicylaldimine)-co-poly(3-hexylthiophene-2,5-diyl) copolymer

Abstract

End-functionalization of polymers and synthesis of copolymers has been reported to be an effective method in tuning intermolecular interactions and electronic energy levels, which is extremely vital for improving the power conversion efficiency (PCE) of organic photovoltaic cells (OPVs). In this work, in-situ synthesis of novel dendritic poly(propylene imine) tetra(salicylaldimine)-co-poly(3-hexylthiophene-2,5-diyl) (P3HT-PSL) copolymer by Grignard metathesis is reported. Prior to performing Grignard metathesis, the poly(propylene imine) tetra(salicylaldimine) (PPI-SL) dendritic core material was synthesized using Schiff base condensation. It is noteworthy that this Grignard metathesis has never been used to grow a linear polymer chain on the four branches of dendritic core material. The properties of synthesized PPI-SL and P3HT-PSL were studied by Fourier-transform infrared (FTIR), small angle X-rays scattering (SAXS), thermal gravimetric analysis (TGA), nuclear magnetic resonance (NMR), ultraviolet–visible spectroscopy (UV–Vis), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and cyclic voltammetry (CV). Effect of poly(3-hexylthiophene-2,5-diyl) (P3HT) chains on the PPI-SL branches were investigated. The formation of P3HT-PSL was confirmed by NMR, FTIR, TGA, and UV–Vis spectroscopy. Synthesized materials were used as donor materials for OPVs and champion PCE of 0.24 % was achieved for P3HT-PSL based OPV. This work uncovers a new avenue for synthesis of organic donor materials for use in OPVs.