Engineering Photophysical Properties of Carbon Quantum Dots for Eco-Friendly Luminescent Solar Concentrators

Chi-Tsu Yuan^1*, H. Y. Huang¹, W. R. Liu², W. C. Chou³

¹Physics, Chung Yuan Christian University, Taoyuan, Taiwan
²Chemical Engineering, Chung Yuan Christian University, Taoyuan, Taiwan
³Electrophysics, National Chiao Tung University, Hsinchu, Taiwan

* Presenter:Chi-Tsu Yuan, email:ctyuan@cycu.edu.tw

Carbon quantum dots (CQDs) are composed of aromatic sp2 carbon skeleton and edge-surrounded functional groups, which exhibit several unique photophysical and materials properties, thus would be eco-friendly and cost-effective alternatives for heavy-metal-containing QDs in a variety of optoelectronic applications. However, several challenges still existed, such as low solid-state quantum yields (QYs), lack of long-wavelength emission and small Stokes shift, which hindered their practical utilization. To address those issues, the strategies based on host-guest interaction and intermolecular coupling can be used to tailor both photophysical and materials properties of CQDs for preparing efficient luminescent solar concentrators (LSCs). By means of spectroscopic techniques, we found that main nonradiative relaxation pathways in CQDs include direct relaxation of the absorbing states via lattice vibration, nonradiative recombination of the emitting states via surface-ligand motion and inter-CQD energy transfer. As a result, bi-functional amino-silane agents were introduced to graft the CQD surfaces, which can be used to passivate the oxygen-related defects and concurrently serve as a rigid silica solid matrix. Indeed, solid-state QYs can be largely enhanced, together with enlarged Stokes shift for the formed CQDs@silica composites. In addition, due to covalent bonding between the guest emitters and host matrix, such high QYs can be maintained at high loading concentration, while still possessing high optical transparency. Efficient LSCs were prepared based on such CQDs, yielding high optical efficiency, which is already comparable with that of the LSCs based on toxic QDs.
References
[1] Chi-Tsu Yuan* et al, J. Phys. Chem. Lett., 11, 9344-9350 (2020).
[2] Chi-Tsu Yuan* et al, Nanoscale 12, 10781 (2020).
[3] Chi-Tsu Yuan* et al, J. Phys. Chem. Lett., 11 , 567 (2020).
[4] Chi-Tsu Yuan* et al, Solar RRL 1, 1-7 (2019).
[5] Chi-Tsu Yuan* et al, ACS Applied Materials & Interfaces 10, 34184 (2018).

Keywords: luminescent solar concentrators, quantum yields, carbon quantum dots