페로브스카이트 광전 소자 및 스마트 LED 콘택트렌즈의 생의학적 응용

Abstract

Numerous light-based diagnostic and therapeutic devices are routinely used in the clinic. Recently, many new ideas have been proposed to realize implantable or wearable functional devices. With its minimal invasiveness, light-based therapy offers therapeutic benefits to improve patient compliance. A variety of phototherapeutic strategies have been developed, including photothermal therapy (PTT), photodynamic therapy (PDT), photobiomodulation (PBM), and optogenetic therapy. Many advances have been enabled by developing multifunctional materials for photonic healthcare devices. Especially, photonic materials have been developed for healthcare devices, such as quantum dots (QDs), mechanoluminescence nanoparticles (MLNPs), gold nanoparticles (AuNPs), and perovskite QDs. In Part I, perovskite QDs were synthesized and developed for clarifying optical properties by tuning ligand length. Formamidinium (FA, CH(NH2)2) lead bromide perovskite (FAPbBr3) QDs are promising emitters due to their high stability and ability to emit pure green color in both film and solution states. Even though various types of metal halide QD emitters in solution have shown high photoluminescence quantum efficiencies (PLQEs), electroluminescence efficiencies of the light-emitting diodes (LEDs) using the QD films are still poor, possibly due to the insulating ligands. Accordingly, the organic ligand of QDs should be designed to facilitate charge injection and transport in LEDs. Here, we synthesized ligand-engineered colloidal FAPbBr3 QDs at room temperature and demonstrated high-efficiency perovskite QD LEDs based on the FAPbBr3 QDs. The control of ligand length reduced trap-assisted recombination and thus maximized the PLQE of FAPbBr3 QDs. The ligand engineering also improved the charge injection and transport capability in FAPbBr3 QD films. With this ligand engineering method, it was possible to achieve maximum current efficiency based on FAPbBr3 QDs. The ligand engineering method reported here would be a simple way to improve the luminescence efficiency of optoelectronic devices based on perovskite QD LEDs. In Part II, stretchable perovskite QD LED was developed using a stretchable active layer that introduced perovskite nanoparticles into a polymer matrix. A stretchable display has been actively researched to apply a display to a wearable device. Because most stretchable displays have serpentine electrodes between LEDs on stretchable substrate, the gap between the LEDs is widened by stretching the substrate. Accordingly, it is necessary to develop an intrinsically stretchable LED to reduce the screen door effect. Here, we developed an intrinsically stretchable perovskite QD LED by introducing perovskite QD in the polymer matrix. The energy band of the polymer matrix must be larger than the energy band of perovskite QD for the energy transfer to perovskite QD. In addition, the polymer matrix has to interact physically with the perovskite QD, so the perovskite QD should be evenly dispersed in the polymer matrix. The stretchable LED was fabricated using the polymer matrix which had high band gap and physical interaction with perovskite QD on TPU substrate. The fabricated LED could be stretched up to 75% and emitted light under the strain. It is expected to be able to provide accurate bio-signal analysis and phototherapy to users by developing a wearable patch-type display through the intrinsically stretchable LED. In Part III, a near-infrared wavelength LED contact lens was developed to prevent diabetic retinopathy in a non-invasive way. Diabetic retinopathy is currently treated by highly invasive repeated therapeutic injections and surgical interventions without complete vision recovery. The PBM has been extensively investigated for emerging photonic healthcare applications to chronic disease using far-red/NIR light. Here, we successfully developed a non-invasive smart wireless far-red/near‐infrared (NIR) light-emitting contact lens to treat diabetic retinopathy with significantly improved compliance. A far-red/NIR LED was connected with an application‐specific integrated circuit chip, wireless power, and communication systems on a PET film, embedded in a silicone elastomer contact lens by thermal crosslinking. After in vitro characterization, it was confirmed that the retinal vascular hyper‐permeability induced by diabetic retinopathy in rabbits was reduced to a statistically significant level by repeatedly wearing a smart far-red/NIR LED contact lens. This smart LED contact lens platform technology would be harnessed for various biomedical photonic applications. In summary, during my Ph.D. course, light intensity was optimized through the ligand engineering of perovskite nanoparticles, and intrinsically stretchable LEDs were fabricated using perovskite QDs. In addition, by applying LEDs to contact lenses, diabetic retinopathy has been prevented in a non-invasive way, paving a new avenue to smart healthcare.