Super-connected graphenic nanosheets via well-oriented bridges of naphthothiadiazole and benzodithiophene-containing donor–acceptors and photovoltaic applications thereof

Abstract

Super-connected nanostructures were developed through bridging reduced graphene oxide (rGO) nanosheets with poly[benzodithiophene-bis(decyltetradecyl-thien)naphthothiadiazole] (PBDT-DTNT) and poly[bis(triiso-propylsilylethynyl)benzodithiophene-bis(decyltetradecyl-thien)naphthobisthiadiazole] (PBDT-TIPS-DTNT-DT) polymers. The higher tendency of conjugated polymers towards the rGO surface increased the thickness of super-connections up to 9–12 nm. The red-shifted and more intensified identifying peaks in ultraviolet-visible spectra and more quenched photoluminescence spectra of PBDT-DTNT/rGO nano-hybrids were ascribed to better π-stacking of PBDT-DTNT chains compared to PBDT-TIPS-DTNT-DT ones onto rGO nanosheets and their stronger donating–accepting features. The presence of TIPS side structures made the arrangement of PBDT-TIPS-DTNT-DTs more difficult. The donor–acceptor nano-hybrids were subsequently applied in the active layers of photovoltaic devices in pure and mixed states with the PBDT-DTNT and PBDT-TIPS-DTNT-DT complex polymers. These types of innovatively designed nanostructures eliminate the need for phenyl-C-butyric acid methyl ester (PCBM) and similar acceptor components. In contrast to poly(3-hexylthiophene) (P3HT)-based delicate morphologies, the active layers based on complex polymers such as PBDT-DTNT and PBDT-TIPS-DTNT-DT reflected coarser phase separations. Super-connected rGO nanosheets templated larger phase separations particularly in the presence of donor polymer chains, and thereby high performance photovoltaics were acquired. The best-performing devices based on PBDT-DTNT/rGO + PBDT-DTNT reflected 11.15 mA cm⁻², 0.67 V, 64% and 4.78% characteristics. External quantum efficiency (EQE) experiments also verified the well-performing photovoltaics based on complex polymers.