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Organic Semiconducting Molecules in Green Solvents


Conjugated oligoelectrolytes (COEs) contain a conjugated backbone and pendant groups with ionic functionalities. This unique structure combines the properties of semiconducting and water solubility. COEs have similar optical and electronic properties as compare to conjugated polyelectrolytes (CPEs), which have been widely studied for their unique combination of semiconductivity and water solubility, COE are relatively easier to be synthesized and purified. Certain COEs, such as DSBN+ and DSSN+, have been shown to spontaneously insert into liposomes and within the membranes of yeast, and to incorporate into the membranes of Escherichia coli leads to improvement of the current generation in MFCs. In order to study whether the structure variation would affect the biocompatibility of COEs and thus affect the performance of related devices, several new COEs in series with various conjugation length, molecular length, substitution groups with different electron withdrawing/donating group have been designed and synthesized.

Organic photovoltaics (OPV) have garnered a large amount of attention due to their potential for making light-weighted, flexible and low-cost devices in large scale application However, despite the power conversion efficiencies (PCEs) of OSC have steadily increased

through improvements in materials design, mechanistic insight and device architectures, less viii

attention has been put on the sustainability of future application. The vast majority of high performing devices with bulk heterojunction (BHJ) structure are deposited out of chlorinated or aromatic solvents, such as chloroform and chlorobenzene, which require harsh preparation, costly clean up procedure. These solvents are quite toxic to environment and human being. Thus, to develop OSC system be processed out of alternative green solvents is of importance to the future application, especially in mass manufacturing. 2-MeTHF is used to process organic solar cell in the work. 2-MeTHF fits within the class of solvents sought from renewable resources and the concept of capitalizing on waste to generate useful chemicals. The power conversion efficiency of the solar cell processed out of 2-MeTHF is over 5%, which is quite decent and comparable to devices that processed out of chloroform. These findings open new opportunities for considering mass production of organic solar cells, and other optoelectronic devices. It also highlights that substantial molecular design may not be fundamentally necessary for opening environmentally benign processing.

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