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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. [ABSTRACT FROM AUTHOR]

Photothermal materials for solar evaporators need to have broad light absorption ability and be able to convert into heat efficiently. At present, organic photothermal materials mainly have the problems of narrow absorption spectrum range and low photothermal conversion efficiency. In recent years, the development of photovoltaic materials has attracted the attention of researchers. However, the application of photovoltaic materials to the field of solar driven water evaporation is still rare. Poly(3-hexylthiophene), P3HT, is a typical p-type conjugated polymer that can achieve high power conversion efficiency. P3HT powder has a solar-thermal conversion efficiency of 11.26%. Its absorption range at 300–900 nm provides effective utilization of sunlight and has the potential as an excellent photothermal conversion material. We loaded P3HT into non-woven fabric to obtain an integrated device for simultaneous water evaporation and thermoelectric power generation, with evaporation rate of 1.04 kg m−2 h−1 and output voltage of 58 mV under 1 kW m−2 simulated solar irradiation. This study enriches the application of traditional photovoltaic materials in the field of solar-heat technique and provides guidance in the construction of solar evaporation devices for water-electricity co-generation. Poly(3-hexylthiophene) (P3HT) powder has a solar-thermal conversion efficiency of 11.26%. P3HT non-woven fabric complex is used to construct a water and electricity co-generation device with evaporation rate of 1.04 kg m−2 h−1 and output voltage of 58 mV under 1 kW m−2 simulated solar irradiation. This study enriches the application of traditional photovoltaic materials in the field of solar-heat technique and provides guidance in the construction of solar evaporation devices. [Display omitted] • P3HT is widely used in photovoltaic cells, but its application in the photothermal materials field has not been studied. • P3HT powder has a solar-thermal conversion efficiency of up to 11.26%. • The evaporation rate and efficiency of P3HT solar evaporator were 1.25 kg m-2 h-1 and 86% under 1 kW m-2 solar radiation. • The evaporation rate and output voltage of P3HT water-electricity co-generator were 1.04 kg m h-1 and 58 mV under 1 sun. [ABSTRACT FROM AUTHOR]