A highly efficient organic solar energy-absorbing material based on phthalocyanine derivative for integrated water evaporation and thermoelectric power generation application

Abstract

Integrated water purification and electricity generation by photo-thermal effect has attracted great attention. However, the central issues are designs of the photothermal materials with efficient utilization of solar energy for water–electricity cogeneration. Herein, an organic-small-molecule phthalocyanine (Pc) derivative with polycyclic conjugated structure, 4OCSPC, has been synthesized. The alkoxy chains with high conformational flexibility were modified to α positions, and the thiophene groups were modified to β positions, which afford this Pc derivative solution processing characteristic and enhance Pc conjugation. Therefore, 4OCSPC exhibits attractive photothermal properties and thermal/photo-stability. In solid state, 4OCSPC has a wide absorption range from 300 to 1000 nm, the molar extinction coefficient (ε) is 4.1 × 10⁵ L mol⁻¹ cm⁻¹ in tetrahydrofuran (THF) at 800 nm, and the solar-thermal conversion efficiency is evaluated to be 17.3% under one sunlight irradiation. The solar-to-vapor efficiency was determined to be 86.6%, and the rate of water evaporation reached 1.262 kg m⁻² h⁻¹. Benefiting from the effective capillary action, a novel synergetically coupled solar-steam and solar-electricity device was designed and prepared, which can attain superior water purification and electricity generation performances. Our work demonstrates the application of photothermal organic-small-molecules with polycyclic conjugated structure in water evaporation and power generation, which provides potential opportunities for freshwater and electricity supply for remote areas.