Spray Coated Colloidal Quantum Dot Films for Broadband Photodetectors

A technique for scalable spray coating of colloidal CdSeTe quantum dots (QDs) for photovoltaics and photodetector applications is presented. A mixture solvent with water and ethanol was introduced to enhance the adhesive force between QDs and the substrate interface. The performance of the detector reached the highest values with 40 spray coating cycles of QD deposition. The photodetectors without bias voltage showed broadband response in the wavelength range of 300-800 nm, and high responsivity of 15 mA/W, detectivity of more than 10¹¹ Jones and rise time of 0.04 s. A large size QD-logo pattern film (10 × 10 cm²) prepared by the spray coating process displayed excellent uniformity of thickness and absorbance. The large area detectors (the active area 1 cm²) showed almost the same performance as the typical laboratory-size ones (the active area 0.1 cm²). Our study demonstrates that the spray coating is a very promising film fabrication technology for the industrial-scale production of optoelectronic devices.