Enhanced photoluminescence of a microporous quantum dot color conversion layer by inkjet printing

Owing to their high color purity, tunable bandgap, and high efficiency, quantum dots (QDs) have gained significant attention as color conversion materials for high-end display applications. Moreover, inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode (micro-LED)-based displays. As a color conversion layer, the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering. Conventional scatterers, such as titanium dioxide microparticles, have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process. In our work, as an alternative approach, we use inkjet printing for depositing a phase separating polymer ink based on polystyrene (PS) and polyethylene glycol (PEG). QD/polymer composite pixels with scattering micropores are realized. The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability. With the presence of the microporous structure, the photoluminescence intensity of the QD film is enhanced by 110% in drop-cast films and by 35.3% in inkjet-printed QD pixel arrays compared to the reference samples.