No abstract

Rocı ´o Ponce Ortiz was born in Marbella (Spain) in 1980. She studied at the University of Malaga where she obtained her degree in Chemical Engineering in 2003 and a Ph.D. in Chemistry in 2008 working on vibrational spectroscopy, electrochemistry, and quantum-chemical calculations of oligothiophene derivatives in Prof. Lo ´pez Navarrete's group. In 2008, she joined Prof. Tobin J. Marks' group at Northwestern University as a postdoctoral researcher. Dr. Ponce Ortiz has published 25 research articles. Her current research interest is molecular electronics for organic thin-film transistors.

We report the synthesis, characterization, and first implementation of a naphtho[2,3-b:6,7-b']dithiophene (NDT)-based donor molecule in highly efficient organic photovoltaics (OPVs). When NDT(TDPP)(2) (TDPP = thiophene-capped diketopyrrolopyrrole) is combined with the electron acceptor PC(61)BM, a power conversion efficiency (PCE) of 4.06 ± 0.06% is achieved-a record for a PC(61)BM-based small-molecule OPV. The substantial PCE is attributed to the broad, high oscillator strength visible absorption, the ordered molecular packing, and an exceptional hole mobility of NDT(TDPP)(2).

The consequence of unpaired electrons in organic molecules has fascinated and confounded chemists for over a century. The study of open-shell molecules has been rekindled in recent years as new synthetic methods, improved spectroscopic techniques and powerful computational tools have been brought to bear on this field. Nonetheless, it is the intrinsic instability of the biradical species that limits the practicality of this research. Here we report the synthesis and characterization of a molecule based on the diindeno[b,i]anthracene framework that exhibits pronounced open-shell character yet possesses remarkable stability. The synthetic route is rapid, efficient and possible on the gram scale. The molecular structure was confirmed through single-crystal X-ray diffraction. From variable-temperature Raman spectroscopy and magnetic susceptibility measurements a thermally accessible triplet excited state was found. Organic field-effect transistor device data show an ambipolar performance with balanced electron and hole mobilities. Our results demonstrate the rational design and synthesis of an air- and temperature-stable biradical compound.