Nonconjugative Planarization through sp³-Carbon Bridging: A Geometry-Guided Design Principle for High Mobility...

Triphenylamine derivatives are essential hole-transport materials, yet their propeller-shaped conformation hinders efficient molecular packing and charge transport. Molecular planarization offers a solution, but conventional ring fusion concurrently alters the π-electronic structure. In this work, a nonconjugative planarization strategy is introduced through the design of sp³-carbon-bridged triphenylamine derivatives NX (x denotes the number of sp³-carbon bridges), effectively decoupling the planarization effect from π-conjugation. The results show that fully planar N3 has an ∼50% reduction in hole reorganization energy (λ_h), a sharper and higher most probable value (m) in its electronic transfer integral (V_h) distribution, and optimized transport pathways. These improvements collectively lead to a 3-4-fold increase in hole mobility (μ_h). Our work clarifies how planarization synergistically suppresses molecular vibrations, enhances electronic coupling, and improves packing to boost transport, providing a geometry-guided design principle for high-performance organic semiconductors.