Evaluating mobility extraction reliability in non-ideal organic transistors utilizing weak epitaxy-grown pentacene films

Organic thin-film transistors (OTFTs) have exhibited enhanced carrier mobilities, albeit often accompanied by non-ideal electrical characteristics, posing challenges in accurately assessing device performance. Therefore, it is critical to understand the reliability of mobility values derived from these non-ideal current-voltage curves. In this study, high-quality pentacene films and their OTFTs were fabricated by using organic weak-epitaxy growth technology. We focused on investigating the relationship between effective mobilities and contact resistance by varying the interlayer thicknesses of MoO3 while maintaining the optimized semiconductor layer unchanged. An inverse correlation between the reliability factors and claimed mobilities is identified. For OTFTs with moderate contact resistance, the effective mobility exhibited minimal variation, remaining within a narrow 10% margin, accompanied high reliability factor. These results indicated the reliability of mobility extraction. Notably, the optimal thickness of MoO3 ranged between 2.0-3.0 nm. In contrast, a thicker MoO3 layer significantly decreased the reliability factor due to a high contact resistance, thereby rendering the effective mobility unreliable. Our works underscore the robustness of the estimation method for OTFTs featuring moderate contact resistance, providing guidance for the evaluation of material and device performance.