Efficient Perovskite Solar Cells Enabled by Facile Synthesis of Triphenylamine-Based Hole-Transport Material with D–A₁–A₂ Structure

In perovskite solar cells (PSCs), the selection of the hole-transport material (HTM) markedly influences both the achievement of high efficiency and overall stability. This study outlines the synthesis of a dopant-free HTM founded on the donor–acceptor₁–acceptor₂ (D–A₁–A₂)-conjugated structure and its integration into PSCs. The ensuing PSCs showcase a power conversion efficiency of 17.8%, comparable to NiO_x inorganic HTM-based devices and surpassing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate polymeric HTM-based devices. The efficiency comparable to NiO_x is attributed to the efficient hole extraction and transport facilitated by the conjugated π junctions in the specifically designed structure. Furthermore, these devices exhibit enhanced stability, maintaining 95% of their initial performance for 60 d in an N₂ atmosphere without encapsulation. The improved stability primarily arises from the hydrophobic nature of the HTM. The larger π-conjugated molecules lead to a denser film by reducing intermolecular space, effectively retarding water intrusion and providing superior protection to the perovskite layer. Thus, the dopant-free D–A₁–A₂ HTM with an extended conjugated π structure not only effectively enhances device efficiency but also substantially improves device stability.