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 (Rc) at the source (Rs). To date, we demonstrate an innovative strategy by depositing an additional different organic semiconductor (OSC) layer onto the initial OSC surface to effectively reduce Rc. 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 (μlin) increased 4-fold─from 0.44 to 1.67 cm2·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 Rs. 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 (μsat) 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 Rc in TC-OTFTs with poor charge injection and low μlin. We confirm that this approach holds promise for practical applications in industrial and commercial OTFT development.