Traditionally, fullerenes have been the dominate electron acceptor used in organic photovoltaics (OPVs) due to their high electron affinity and good crystallinity. However, fullerenes are expensive, absorb poorly in the visible region, and their electronic properties are difficult to tune. Recently, efforts have increased toward developing new non-fullerene small molecule n-type materials to overcome these inherent deficiencies. The major advantages of non-fullerene n-type semiconductors is their ability to increase short circuit current, J<sub>sc</sub>, open circuit voltage, V<sub>oc</sub>, and improved processability, photostability, and inexpensive starting materials. Through systematic molecular design we developed novel n-type semiconductors, asymmetrically substituted diarylindenotetracenes (ASIs). Here the synthesis and characterization of asymmetrically substituted indenotetracenes, a novel class of n-type semiconductor, will be shown. We were able to tune the electronics of ASIs through late stage derivatization. To evaluate the potential effectiveness of ASIs as an electron transport layer in OPVs, their electronic and physical properties were studied as well as theoretical charge transport. Electronic properties were evaluated using cyclic voltammetry and, UV–visible and fluorescence spectroscopy. ASI derivatives were found accept two electrons and efficiently absorbs light in the visible region with very poor corresponding fluorescence. Solid state properties of ASIs were characterized via single crystal X-ray, thermogravimetric analysis, and differential scanning calormatery. ASIs demonstrate high decomposition temperatures, efficient π–stacking in the solid-state, and stable crystal structures. Also, electron transport calculation, using solved crystal structures, indicate ASIs would function efficiently as a novel electron transport material.

Synthesis and characterization of asymmetric indenotetracenes: Novel n-type organic semiconductors for use in organic photovoltaics

253rd National Meeting (2017)

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