Spray deposited PbS colloidal quantum dot solid for near infrared photodetectors
Abstract Colloidal PbS quantum dots (QDs) are promising candidates for various optoelectronic applications based on solution processed thin film techniques. In this work, a versatile layer by layer (LBL) spray deposition of the QDs is introduced aiming for a future large scale fabrication process of optoelectronic devices. As compared to spin coated QD solids, a smaller inter dot distance and a better ordered superlattice stacking behavior of the QDs are found in the spray deposited QD solids as confirmed by grazing incidence small angle X ray scattering (GISAXS) The spectral mapping combined time resolved photoluminescence analysis indicates a longer charge carrier lifetime and better order of the energy state distribution of the spray deposited QD solid comparing with the spin coated one. Thus, photodetectors based on spray deposition of QD solids demonstrate an excellent device performance, with the responsivity achieving 365.1 A/W and the detectivity reaching up to 1.4 x 1012 Jones under an illumination power of 63.5 mW/cm2 at a wavelength of 1250 nm. The spray deposited device performances indicate a great potential of spray deposition of large sized QDs in large scale fabrications for optoelectronics using longer wavelengths.