This conference presentation, “New ligands and approaches to RSA materials” was presented at the Organic Photonic Materials and Devices XXIV conference at SPIE Photonics West 2022.

Imidazopyridine derivatives are purine isosteres that display interesting optical properties and biological applications. Here one reports a spectroscopic investigation in six imidazopyridines derivatives with different chemical groups, leading to changes in the photophysical parameters and nonlinear optical properties. Fluorescence quantum yield, lifetime and anisotropy were performed to obtain information to interpret the nonlinear optical response. The two-photon absorption cross-section spectrum, measured by the Z-scan technique, was modeled by the sum-over-state approach. Higher 2PA cross-section was observed when two electron acceptor groups were added to the imidazopyridines core. Yet, the spectral position of higher excited states was show to contribute to the 2PA cross-section.

Semi-transparent organic photovoltaics (ST-OPVs) are considered as an attractive solution for power-generating windows. Typically, the module geometric fill factor (GFF) is limited by low-resolution patterning approaches. Here, we demonstrate a solvent-free polymer-based peel-off patterning method, which can achieve the resolution of photolithographic patterning of chemically sensitive organic materials. An ~13 cm² ST-OPV module fabricated using this method, achieves GFF > 95%, and a power conversion efficiency approaching 8% which shows less than 10% loss compared to a 4 mm² device. This method enables a viable path for achieving ST-OPVs at larger scales.

In this work, we improved charge carrier separation efficiency through a g-C3N4/GaN NRs heterostructure device. We characterized the properties of the g-C3N4/GaN NRs device with detecting the UV light and sensing NO2 gas at room temperature. The device showed high responsivity and detectivity under zero bias conditions due to the built-in field at the interface of the heterostructure. The performance of the heterostructure was stimulated under UV light illuminations with 2.3 times higher response compared to the darkness. In addition, the device response to NO2, NH3, H2, H2S and CO ambient gases at RT were measured, the device exhibited high response to NO2 gas. The low activation energy promoted to capture NO2 gas molecules.

Ultra-high frequency electric field detection such as terahertz electric field is one of the most important terahertz technologies, and various applications are expected in fields of terahertz science and ultra-high-speed wireless communication. In this research, we have developed a new fabrication technique for producing free-standing films of poled EO polymers and laminated films with various film thicknesses for a high-efficiency and wideband THz wave detection using Pockels effect or Stark effect of EO polymers. For this purpose, polycarbonate (PC) based EO polymers with a high glass transition temperature and robustness are used.

We developed a high-performance EO polymer for visible light by adopting figures of merit (FOMs) including wavelength factors to compare the performance of EO polymers over a wide wavelength range. We found EO polymers whose FOMs at 640 nm are larger than those at 1550 nm of the C-band EO polymer. A modulator using the EO polymer for visible light gives that the modulator’s figure of merit, VpiL is as small as 0.65 V·cm, which is smaller than the typical value of C-band EO polymer modulators.

EO polymer/silicon hybrid optical modulators have attracted much attention to their potential use of the optical interconnects in data center for small drive voltage and low-power-consumption. We investigated the photochemical stability of our synthesized O-band compatible EO polymer under irradiation by using a continuous-wave 1310-nm laser. In this presentation, we will report the results of the temperature dependence of the rate constant. Based on the results obtained, we will discuss the effects of excited singlet oxygen on the photochemical stability of the EO polymers.

The deoxyribonucleic acid (DNA) – a new “green” biomaterial is intensively studied in the last years, due to its promising applications in organic photonics and organic opto-electronics. The light emission properties of the solutions in butanol of the biopolymer complex formed by deoxyribonucleic acid (DNA) – cetyltrimethylammonium chloride (CTMA) surfactant doped with different concentrations of Rhodamine 610 (Rh610) dye were investigated. We will present our results concerning several important parameters of the laser emission process, meaning the emission wavelength, the threshold and the efficiency of the lasing. The influence of the biopolymer environment on the lasing was assessed by a comparative study of laser emission in solutions of Rh610 in butanol, at the same concentrations, with and without DNA-CTMA. Acknowledgement This work was supported by a grant of the Romanian Ministry of Research, Innovation and Digitization, CCCDI-UEFISCDI, project number PN-III-P2-2.1-PED-2019-2

I will introduce our research progress in using polyaniline for mid-IR emissivity tuning and comparative study of the ordinary planar device versus metasurface design. Polyaniline has the suitable and tunable plasmon frequency to work as a dynamic mid-IR material. The metal-insulator transition driven by electrochemical reaction is significant and non-volatile, ideal for long-term wearable thermoregulation. The metamaterial approach is based on metal-insulator-metal perfect absorber configuration, with rational material design to enable electrochemical dynamic switching of absorptivity/emissivity. I will also share our characterization of polyaniline’s mid-IR electrochromic properties and refractive index, hoping to enrich the material palette for the tunable mid-IR photonics research community.