Rational synthesis of a polymerizable fullerene–aniline derivative: study of photophysical, morphological and photovoltaic properties $$^{\S }$$ §

Abstract

This paper describes the synthesis of a polymerizable, aniline appended fullerene derivative, 3-aminobenzyl-phenyl- $$\hbox {C}_{61}$$ -butyrate (PCBAn) and its corresponding polymer (P-PCBAn), and detailed photophysical and morphological analysis towards application as an acceptor in polymer solar cells (BHJ-PSCs). The poly-3-aminobenzyl-phenyl- $$\hbox {C}_{61}$$ -butyrate (P-PCBAn), having a substituted polyaniline (PANI) skeletal structure, was synthesized via $$\hbox {FeCl}_{3}$$ oxidative polymerisation of PCBA in its non-conducting leucoemaraldine state. HOMO and LUMO energies estimated using optical and electrochemical techniques revealed upshifted LUMO levels for PCBAn ( $$-$$ 3.68 eV, $$\Delta \hbox {E} = 0.1$$ eV) and P-PCBAn ( $$-$$ 3.66 eV, $$\Delta \hbox {E} = 0.12$$ eV) compared to the parental fullerene derivative, PCBM ( $$-$$ 3.78 eV). The morphologies of PCBAn and P-PCBAn individually and in polymer blends with P3HT were investigated using AFM and TEM analysis, which showed nanoflake-like aggregates for P3HT/PCBAn and a favourable interconnected nanonetwork structure for P3HT/P-PCBAn. The wide angle X-ray scattering (WAXS) studies of PCBAn films drop-cast from THF/water (3:7) mixture and P-PCBAn films drop-cast from 1,2-dichlorobenzene exhibited plane reflections of lamellar mesophases with d-spacing of 3.4 nm and 3 nm for PCBAn and P-PCBAn, respectively. The fluorescence quenching experiments with P3HT indicated efficient electron transfer from P3HT to P-PCBAn when compared to PCBAn. The fabrication of an inverted BHJ-PSC device using PCBAn and P-PCBAn as an acceptor in combination with P3HT showed PCE of 0.9% and 1.1%, respectively, showing considerable enhancement in the case of the polymeric acceptor. The polymeric acceptor and the rational design strategy used here could open up new opportunities in the PSC device fabrication. Ref.: Ms. No. JCSC-D-18-001042 SYNOPSIS Synthesis of a polymerizable, aniline appended fullerene derivative, 3-aminobenzyl-phenyl- $$\hbox {C}_{61}$$ -butyrate (PCBAn) and its corresponding polymer, and detailed photophysical and morphological analysis towards application as acceptor in polymer solar cells (BHJ-PSCs) are reported. The results suggest bicontinuous interpenetrating network and better charge transport properties for P3HT:P-PCBAn polymer blend compared to P3HT:PCBAn.