Coordination-induced p-type selectivity and enhanced hole mobility in an ambipolar organic semiconductor via electron passivation

Abstract

A unipolar organic semiconductor with high mobility is crucial for various optoelectronic devices. In this study, a benzo[c]cinnoline-based organic semiconductor (TPA)₂Ab with ambipolar transport properties is converted into a unipolar (p-type) semiconductor by reacting with the Lewis acid palladium tetrachloride (PtCl₄). This reaction reduces the hole trap-state density of (TPA)₂Ab from approximately 10¹⁶ cm⁻³ to a level where a measurable trap-filled limit (V_TFL) cannot be detected in the resulting [(TPA)₂Ab]PtCl₄ complex. Consequently, the hole mobility increases significantly from 3.4 × 10⁻⁵ to 3.9 × 10⁻³ cm² V⁻¹ s⁻¹, followed by a reduction in electron mobility from 1.4 × 10⁻⁵ to 4.1 × 10⁻⁷ cm² V⁻¹ s⁻¹.