Exploring π-conjugated triphenylamine–cyano derivatives as cost-effective hole-transporting materials in perovskite solar cell

Abstract

The rapid progress in the power conversion efficiency (PCE) of perovskite solar cells (PSCs), along with the limitations of the benchmark hole-transporting material (HTM) spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene], has driven the search for alternative HTMs. In this study, triphenylamine, cyano groups, and cyanopyridone/pyridine cores were employed in the design and synthesis of two new HTMs: TPA-CN and TPA-CNA. Comprehensive structural, photophysical, electrochemical, thermal, and density functional theory (DFT) studies revealed suitable HOMO–LUMO energy levels, optical bandgaps of 2.72–2.86 eV, and high glass transition temperatures of 120 °C and 166 °C for TPA-CN and TPA-CNA, respectively. Xerographic time-of-flight measurements showed hole mobilities of ∼3.6 × 10⁻⁵ and 3.5 × 10⁻⁵ cm² V⁻¹ s⁻¹ for TPA-CN and TPA-CNA, respectively. These findings demonstrate the promise of π-conjugated synthetic compounds as efficient HTMs in PSCs, offering pathways for enhancing device performance and improving cost-effectiveness in renewable energy applications.