Charge Transport through Functionalized Graphene Quantum Dots Embedded in a Polyaniline Matrix

Abstract

Nitrogen-functionalized graphene quantum dots embedded in a polyaniline matrix (NGQD-PANI) are extremely promising candidates for the development of next-generation sensors and for thermoelectric materials design with the distinct advantage of tunability of electronic properties by controlled doping and/or by controlling the inherent disorder in the microstructure. While their application is increasing in photovoltaics, energy storage, and sensing technologies, a clear understanding of conduction in these hybrid systems is lacking. Here, we report a comprehensive study of NGQD-PANI composites with varying NGQD doping levels over a wide range of temperature. We show distinct regimes of conduction as a function of temperature, which include: a transition from Efros-Shklovskii and Larkin-Khmelnitskii variable range hopping at low temperatures to thermally driven electron transport at higher temperatures. Importantly, we find a remarkable 50-fold enhancement in conductivity for 10% NGQD-doped samples and tunability of the crossover temperature between different regimes as a function of the applied voltage bias and doping. Our work provides a general framework to understand the interplay of extrinsic parameters like temperature and voltage bias with intrinsic material properties like doping, which drives the electronic properties in these hybrid systems of technological importance.