The fundamental contact limit in organic electronics defined by Maxwell–Wagner resistance

Abstract

Contact resistance in organic electronic devices has traditionally been attributed to injection barriers from work function mismatches. Here, we identify a fundamentally different mechanism: space charge accumulation due to dielectric relaxation time mismatch between metals (∼10−15 s) and organic semiconductors (10−6–100 s). This Maxwell–Wagner charging creates interface resistance independent of energetic barriers. We develop a dual-mechanism framework distinguishing injection-limited contacts (high barriers, voltage-dependent activation energies) from Maxwell–Wagner dominated contacts (low barriers, voltage-independent behavior). The model predicts absolute contact resistance RMW=τ2δ/(ε0εrWLc). Experimental validation using pentacene organic field-effect transistors shows quantitative agreement: predicted Maxwell–Wagner resistance (∼38 kΩ cm) matches gold contact measurements (35.3±5.6 kΩ cm), while silver contacts follow the classical Schottky behavior. This establishes a fundamental resistance floor that cannot be overcome through energy level alignment alone, fundamentally changing contact optimization strategies and setting intrinsic performance limits for organic electronics.