Energy conversion and storage via photoinduced polarization change in non-ferroelectric molecular [CoGa] crystals
Pritam Sadhukhan, Shu‐Qi Wu, Shinji Kanegawa, Shengqun Su, Xiaopeng Zhang, Takumi Nakanishi, Jeremy Ian Long, Kaige Gao, Rintaro Shimada, Hajime Okajima, Akira Sakamoto, Joy G. Chiappella, Myron S. Huzan, Thomas Kröll, Dimosthenis Sokaras, Michael L. Baker, Osamu Sato
Abstract
Abstract To alleviate the energy and environmental crisis, in the last decades, energy harvesting by utilizing optical control has emerged as a promising solution. Here we report a polar crystal that exhibits photoenergy conversion and energy storage upon light irradiation. The polar crystal consists of dinuclear [CoGa] molecules, which are oriented in a uniform direction inside the crystal lattice. Irradiation with green light induces a directional intramolecular electron transfer from the ligand to a low-spin Co III centre, and the resultant light-induced high-spin Co II excited state is trapped at low temperature, realizing energy storage. Additionally, electric current release is observed during relaxation from the trapped light-induced metastable state to the ground state, because the intramolecular electron transfer in the relaxation process is accompanied with macroscopic polarization switching at the single-crystal level. It demonstrates that energy storage and conversion to electrical energy is realized in the [CoGa] crystals, which is different from typical polar pyroelectric compounds that exhibit the conversion of thermal energy into electricity.