High sensitivity organic negative temperature coefficient thermistors based on rylene diimide derivatives

Abstract

The development of organic temperature sensors is critical for advancing next-generation technologies such as artificial skin, soft robotics, and wearable electronics. To date, improving the temperature sensitivity of flexible temperature sensors has remained a significant challenge. Organic semiconductors with a negative temperature coefficient (NTC) show a highly sensitive temperature–resistance response, giving them great potential for use in flexible temperature sensors. This study investigates how molecular structures govern the negative temperature coefficient (NTC) effect in organic thermistors using three rylene diimide derivatives, namely naphthalene diimide (NDI), perylene diimide (PDI), and terylene diimide (TDI). Systematic conjugation extension yielded tunable energy gaps (1.9–2.9 eV) and altered crystalline packing due to reduced core steric hindrance. The resulting thermistors showed distinct resistance–temperature (R–T) correlations, revealing a direct link between molecular packing, energy gaps, and responsivity. Their R–T curves exhibit a two-stage characteristic due to differing conduction mechanisms. PDI-based devices achieved a wide linear range (123–473 K) and a high sensitivity of −7.4%/K, demonstrating competitive performance among reported organic thermistors. These findings provide fundamental insights for designing optimized organic NTC thermistors.