Optoelectronic Stress Sensor Based on a Quantum Dot-Organic Semiconductor Nanocomposite

We studied the electrical and optical responses of a sensor device based on a nanocomposite comprising CdSe quantum dots (QDs) embedded in an organic matrix to compressive stresses. The sensor converted stresses as low as a few kPa into measurable changes in both current density and electroluminescence (EL) intensity. Two distinct operation regions have been identified: at low stresses below 200 kPa, a moderate increase in current density and a sharp decrease in EL intensity with increasing stress were observed; at high stresses above ~200 kPa, a large increase in current and slow EL quenching were obtained. These behaviors have been attributed to stress-induced increases in the rates of charge hopping and excitonic energy transfer in the nanocomposite. Similar devices may be built on flexible substrates and used to directly image stress distributions and sense touch on a par with human fingers.