Developing colloidal nanoparticles for inkjet printing of devices with optical properties tuneable from the UV to the NIR

Abstract

Colloidal low-dimensional photo-sensitive nanomaterials have attracted significant interest for optoelectronic device applications where inkjet printing offers a high accuracy and low waste route for their deposition on silicon-based, as well as flexible, devices. However, to achieve photodetection and displays with absorption and emission tuneable across the range from the ultraviolet (UV) to the near infrared (NIR), the availability of printable optically active materials needs to be addressed. In this work we develop printable ink formulations of graphene quantum dots (GQDs), NaYF₄:(20%Yb and/or 2%Er doped) upconverting nanoparticles (UCNPs), and PbS quantum dots (QDs) and demonstrate their use in devices such as graphene-based photodetectors and fluorescent displays. The ink formulations, printing strategies and post-deposition techniques were developed and optimised to enable the deposition of photo-sensitive nanomaterial layers in a controllable manner onto flexible polymeric, glass and silicon substrates. The nanomaterials retained their properties post deposition, as we exemplify by photosensitisation of single layer graphene (SLG) photodetector devices, with spectral responsivity tuneable from the UV for GQD/SLG to the NIR for UCNP/SLG and PbS/SLG devices, with photoresponsivity up to R ∼ 10³ A W⁻¹. Fluorescent displays were also demonstrated consisting of CsPbBr₃ perovskite nanocrystals and UCNPs inkjet printed onto flexible transparent substrates, for selective sensing of UV and NIR light. This work successfully expands the material library of printable optically active materials and demonstrates their potential for printed optoelectronics, including flexible devices.