Indacenodithiophene (IDT) and indacenodithienothiophene (IDTT)-based acceptors for non-fullerene organic solar cells

Non-fullerene organic solar cells (NFOSCs) have attracted great deal of attention among researchers in last five years owing to the superior optoelectronics properties of non-fullerene acceptors (NFAs) compared to fullerene derivatives, such as structural versability, suitable energy levels, broad absorption and tunable morphology. The emergence of NFAs offer the opportunity to develop high-performance NFOSCs with a power conversion efficiency (PCE) of over 15%, which indicates that designing and applying new conjugated materials is the crucial factor to enhance the photovoltaic performance. NFAs based on indacenodithiophene (IDT) or its extending backbone core indacenodithienothiophene (IDTT) and end-capped with strong electron-deficient groups have several advantages, such as strong absorption in the visible and Near-Infrared (NIR) region and good alignment of energy levels, indicating that they can be attractive candidates as acceptor materials in OSCs. In this perspective, we discuss the recent advancement made in IDT and IDTT-based NFAs and their photovoltaic device performance. We will mainly concentrate our discussion on the benefits of each NFA in conjunction with the matched conjugated polymer donor in the context of donor/acceptor (D/A) blends correlating it to device performance.