Study on carrier excitation and accumulation effects in organic dual planar-bulk heterojunctions and their application in OFETs

Abstract

This study proposes an organic dual-planar bulk heterojunction structure (DP-BHJ) to address the long-standing structural contradiction in organic field-effect transistors (OFETs) where the improvement of conduction performance is often accompanied by an increase in off-state leakage current. By introducing an ultra-thin P:N blend layer (pentacene:F₁₆CuPc) between P-type pentacene and N-type F₁₆CuPc, the structure forms a synergistic architecture of double planar heterojunctions and a bulk heterojunction in the vertical direction. In the on-state, the synergistic effect of two built-in electric fields in the same direction in this structure effectively enhances carrier excitation and accumulation, thereby significantly improving the on-state current and mobility; in the off-state, the interface modulation effect introduced by the blend layer effectively restricts interface carriers, leading to a significant suppression of off-state current. Compared with traditional planar heterojunction devices, the OFETs based on this structure achieve bidirectional optimization of on-state and off-state currents without sacrificing conduction performance: the mobility and on-state current are increased by approximately 2.4 times and 2.9 times, and the threshold voltage is reduced by approximately 50%. Furthermore, through the fine modulation of the heterojunction interface by introducing an ultra-thin blend layer, the off-state current is effectively reduced from 9.19 × 10⁻⁸ A to 1.83 × 10⁻⁸ A.