Novel dicyanomethylene-functionalized s-indacene-tetraone-based materials as non-fullerene acceptors for ternary organic solar cells

Organic materials are actively researched for their potential application in the manufacturing of solar cells. The possibility to vary the structure of the molecules and the possibility of using wet casting methods such as spin-coating or inkjet printing are the main advantages of these materials. In recent years the research has shifted away from fullerenes as electron acceptor materials due to their disadvantages. Additionally, the introduction of a third component in the active layer of organic solar cells allows the expansion of the absorption spectrum of the cell thus increasing the solar cell efficiency compared to the two-component bulk heterojunctions. The manufacturing of ternary organic solar cells (TOSC) is easier than tandem cells, thus reducing the potential costs upon their commercialization.

In this work, we have studied the application of novel dicyanomethylene-functionalized s-indacene-tetraone based non-fullerene acceptors IC-1 and IC-2 as the third component in TOSCs. The chromophores IC-1 and IC-2 with donor-acceptor-donor (D-A-D) molecular composition were acquired by condensation reactions between s-indacene-tetraone derivative acceptor fragment and aniline- or indoline-based electron-donating fragments. Electron donor polymer PM6 and electron acceptor material Y7 were used as the base materials for the TOSCs. The energy levels of IC-1 and IC-2 are located between the levels of PM6 and Y7 creating the cascade effect. IC-2 absorption has an additional shoulder between 650 nm and 800 nm which helps to increase the power conversion efficiency and reduce the losses shown by the external quantum efficiency (EQE) measurements.