Fan-Yi Meng, I-Han Chen, Jiun-Yi Shen, Kai-Hsin Chang, Tai-Che Chou, Yi-An Chen, Yi-Ting Chen, Chi-Lin Chen & Pi-Tai Chou

Nature Communications 13, Article number: 797 (2022)

https://www.nature.com/articles/s41467-022-28489-0

Abstract
We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular composites based on the TADF core phenoxazine–triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S1-T1 energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule’s triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.

Keywords: LIGHT-EMITTING-DIODESORGANIC; MATERIALS; AB-INITIO; CIS-FORM; NORBORNADIENE; QUADRICYCLANE; ISOMERIZATION; PHOTOISOMERIZATION; DERIVATIVES; DENDRIMERS.