ИСТИНА

The most efficient organic solar cells (OSC) are based on bulk heterojunction that is formed by the nanoscaled interpenetrating phases of two different organic semiconductors, one of which is an electron donor, and the other is an electron acceptor. Nowadays the efficiency of OSC has risen up to 12%, mainly due to development of new donors, while as acceptors a few fullerene derivatives are commonly used. However fullerenes have a number of disadvantages: low optical absorption, restricted possibilities for energy level tuning, low stability. This encourages researchers to develop new non-fullerene acceptors [1,2]. In this work, we propose a number of such acceptors based on dicyanovinyl-substituted linear and star-shaped oligothiophenes (Fig.) and study their potential for organic solar cells. All these acceptors show the electron affinity in the range 3.4 – 3.5 eV according to electrochemical measurements; it is lower than for fullerene derivatives, and therefore one can expect higher open-circuit voltage (Voc). The absorption range and molar absorption coefficient of the oligothiophene acceptors are close to those of polythiophenes. The electron mobility for some acceptors was measured to be up to 310-3 cm2/(V s), which is no less than for the common fullerene derivative, PCBM. We fabricated OSC based on the oligothiophene acceptors and poly-3-hexylthiophene as donor with Voc near 0.8 – 0.9 V, which is higher than those for the fullerene-based ones. The effects of molecular structure of non-fullerene acceptors on OSC performance will be presented. 1. V.A. Trukhanov, D.Yu, Paraschuk, Non-fullerene acceptors for organic solar cells. Polymer Science Series C, accepted for publication. 2. P. Sonar, J.P.F. Lim, K.L. Chan, Organic non-fullerene acceptors for organic photovoltaics. Energy Environ. Sci. 4, 1558 (2011).