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 work, triphenylamine, cyano groups, and cyanopyridone/pyridine cores were employed to design and synthesize 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 band gaps of 2.72-2.86 eV, and high glass transition temperatures of 120 °C and 166 °C, 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. These findings demonstrate the promise of π-conjugated synthetic compounds as efficient HTMs in PSCs, offering pathways to enhance device performance and improve cost-effectiveness in renewable energy applications.