Laboratory of Organic Photofunctional materials has been researching the wide range of organic materials for display devices. Recently, our group has been focused on the design of highly stable organic dyes for optical filters such as UV absorbers, LCD color filters, and near-infrared absorbing films.

Ultraviolet (UV) designates a band of the electromagnetic spectrum with wavelengths from 10nm to 400nm and contributes about 10% of the total output of the sun. Notably, high energy UV-A (320 to 400 nm), UV-B (290 to 320 nm), and UV-C (200 to 290 nm) have harmful effects on the organic polymer such as photo-degradation.

Excited state intermolecular proton transfer (ESIPT) UV absorber is a fascinating class of UV absorbing materials, and it can efficiently reduce the photo-degradation by absorbing UV radiation instead of the polymer. ESIPT UV absorbers exhibit excellent absorption in UV wavelength regions, and they are fundamentally robust due to intra/inter molecular hydrogen bonding between proton donor and acceptor. Therefore, ESIPT UV absorber is an outstanding candidate to use in the protection of polymer requiring harsh environment applications such as automotive and outdoor.

Spectral conversion of solar radiation from green to red light can enhance the photosynthesis efficiency of chlorophyll. This can lead to significant increase in bioproductivity. Fluorescent organic materials which convert wavelengths of light from green(500–570nm) to orange-red(580–650nm) can be used as the colorants for the photoconversion films. We also aim for development of novel AIEE(Aggregation Induced Emission Enhancement) luminogens which display higher photoemission even in the aggregated state. General organic fluorophores exhibit significantly decreased quantum efficiency when applied to film as known as the ACQ(Aggregation Caused Quenching) effect, while AIEE luminogens are free from this unfavored effect.

The first near-infrared (near-IR) absorbing organic compounds were synthesized at the beginning of 1900s. There are a great number of organic compounds that absorb intensively above 700 nm and up to about 1300nm due to electronic excitation. The basic acyclic near-IR chromophores (polymethine dyes) as well as the basic cyclic near-IR chromophores (annulenes, porphyrines, and squarine) are well known. They can be widely modified through substitution, annelation, complex formation, etc. Recently, near-IR dyes are used for new applications such as optical sensor and filter.

Fluorescence is the emission of light observed when some chemical elements or organic compounds are irradiated. As an organic fluorophore absorbes a photon, fluorophore is promoted to a high electronic level as illustrated by the Jablosnki diagram. In the excited state the molecule undergoes very fast non-radiative energy dissipation processes and transition toward the lower sub-vibration level of the exited state. The remaining excess of energy is released in form of light at characteristic wavelengths which is so called fluorescence emission. Our laboratory focuses on the design and synthesis of novel fluorescent dyes by tailoring the fluorescent molecules with functional groups using organic chemistry.

We are specialized in molecular designing strategies to enchance the photophysical properties, solubility, and photostability of dyes for intended application. Organic fluorescenct materials are in demand on various areas such as bioimaging, chemical sensors, light conversion film, and safety garmets. Recently, organic fluorescence materials are under emerging interest on renewable-energy area for application on microalgae biofuel production, and luminescent solar concentrator.

Photodynamic therapy(PDT) is an emerging therapeutic modality for the treatment of tumor cells which has widely attracted a lot of interest as advanced treatment for a variety of cancers. PDT utilizes singlet oxygen(1O2) generated from the triplet excited state of photoexcited photosensitizers, which are an extremely active transient species responsible for necrosis of malignant tumor cells. However, common organic dyes suffer from low singlet oxygen quantum yield for practical PDT application. Controlled design of photosensitizer molecules for high singlet oxygen productivity is critical for further development of photosensitizers for PDT. In our research team, we design the photosensitizers with donor-acceptor(D-A) structure for enhancement of intersystem crossing followed by increased singlet oxygen quantum yield.

Covalent Organic Framework (COF) has been reported as a new species of material in 2005. Various COF materials have been synthesized through changes of the building units since it was reported. COF materials are widely applied to gas storage, gas capture, catalysis, and electrode because of its excellent stability and material properties based on porous structure. In our groups, we are trying not only to develop new COFs which are composed of various building units, but also apply it to photocatalyst, removal of metals, electrode of energy devices.