An Interfacial Additional Organic Semiconductor Layer for Enhanced Charge Injection in Top-Contact Organic Transistors

The misaligned energy level between metallic electrodes and the organic semiconductor (OSC) causes inefficient charge injection in organic thin-film transistors (OTFTs), leading to an increased contact resistance ( R c ) at the source ( R s ). To date, we demonstrate an innovative strategy by depositing an additional different organic semiconductor (OSC) layer onto the initial OSC surface to effectively reduce R c . Herein, we investigate top-contact bottom-gate (TCBG) S-shaped dinaphtho[2,1- b:2′,1′- f ]thieno[3,2- b ]thiophene-10 (S-DNTT-10)-based OTFTs and found that the linear-mode field-effect mobility (μ lin ) increased 4-fold─from 0.44 to 1.67 cm 2 ·V –1 ·s –1 ─after thermally depositing a pentacene thin film on S-DNTT-10, resulting in TCBG S-DNTT-10/pentacene-based OTFTs that possessed a decreased measured R s . Meanwhile, the configuration of TCBG S-DNTT-10/pentacene-based OTFTs was optimized by restricting pentacene deposition to the source area only and effectively improved the reduced saturation-mode field-effect mobility (μ sat ) of initial TCBG S-DNTT-10/pentacene-based OTFTs, which was likely caused by increased drain contact resistance. Through this study of S-DNTT-10-based OTFTs, we present an effective approach to address the crucial challenge of high R c in TC-OTFTs with poor charge injection and low μ lin . We confirm that this approach holds promise for practical applications in industrial and commercial OTFT development.