Manipulating Molecular Motion of [1,2,5]Thiadiazolo[3,4‐g]Quinoxaline‐6,7‐Dicarboxylate Small Molecules for Highly Efficient Solar‐Thermal Water Evaporation and Thermoelectric Power Generation

Abstract Organic conjugated molecules are a category of high solar harvesting material that can convert energy into heat and be utilized as solar‐driven water‐electricity co‐generation. However, the limited absorption range and insufficient photothermal conversion efficiency hinder their application. Herein, two new organic molecules TPA‐BTQ and TPA‐SBTQ, featuring strong electron withdrawing [1,2,5]thiadiazolo[3,4‐ g ]quinoxaline‐6,7‐dicarboxylate (BTQ) center, terminated by triphenylamine or thiophene‐bridged triphenylamine are designed and synthesized. Detailed theory calculations and spectral analysis confirm that the BTQ unit induces strong intramolecular charge transfer and expands the absorption across a wide spectra range. The flexible alky chain substituted on thiophene inhibits the over‐aggregation and affords more rotation space, leading to suppressed radiative transition and efficient solar‐thermal conversion. Therefore, TPA‐SBTQ powder shows broad absorption across 350 to 1300 nm with a high photothermal conversion efficiency of 18.28% under 1 kW m −2 simulated solar irradiation. Moreover, TPA‐SBTQ is further explored for solar‐thermal conversion applications. The evaporation rate of TPA‐SBTQ solar‐driven water evaporator can reach a remarkable 1.337 kg m −2 h −1 with 92% of water evaporation efficiency under 1 kW m −2 solar irradiation. This study provides guidance for the rational design of high‐efficient organic solar‐thermal materials with a wide absorption spectrum and excellent photothermal conversion efficiency at the molecular level for emerging photothermal‐related applications.