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Host material with appropriate thermal stability and solubility is essential for inkjet printing (IJP) organic light-emitting diodes (OLEDs).Herein, three new host materials with different molecular symmetries have been designed for IJP OLEDs.

An A–D–A type acceptor CC10 with an asymmetric D unit has been designed and synthesized by introducing an alkylbenzene unit into a symmetric acceptor CC5. Compared with the symmetric CC5, the asymmetric CC10 showed a similar absorption range and energy level, but better π–π stacking, enhanced electron mobility and optimized microscopic morphology. As a result, the CC10-based organic solar cells demonstrated a high PCE of 11.78%, better than that of 6.91% for CC5-based devices. The significantly improved device performance caused by only a minor modification in the molecular backbone indicates that there is substantial potential of the asymmetric strategy for designing high performance active layer materials.

Two non-fullerene small molecule acceptors (NF-SMAs) NT-4F and NT-4Cl with halogenated end groups were designed and synthesized. When blended with PM6, the NT-4Cl-based binary device gave a power conversion efficiency (PCE) of 11.44% with a fill factor (FF) of 74.1% while the NT-4F binary system showed a PCE of 9.46%. To further broaden the absorption profile and fine-tune the morphology, NCBDT-4Cl, an acceptor with a similar chemical structure and identical molecular orientation to NT-4Cl, was selected as a combinatory component to the PM6:NT-4Cl system. As a result, the ternary device achieved a dramatically promoted PCE of 14.55% with a synergistically enhanced FF of 77.1% and a Jsc of 20.99 mA cm−2 as well as a decreased energy loss (Eloss) of 0.51 eV, which represents the best performance for NT-based NF-SMAs to date.

A cyclopentadithiophene (DTC)-bridged acceptor–donor–acceptor (A–D–A) backboned small molecule acceptor (SMA), namely IDTC-4Cl, was designed and synthesized. In combination with strong electron-withdrawing (5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)dimalononitrile as a terminal group, IDTC-4Cl exhibits a near-infrared light absorption with an edge over 900 nm. Using PBDB-T as the polymer donor, the IDTC-4Cl based device gives a PCE of 9.51% with a Voc of 0.822 V, FF of 60.2% and Jsc of 19.14 mA cm−2. Upon introduction of PC71BM as the third component, the ternary OSCs show an enhanced PCE of 10.41% with a much improved FF of 65.6%, which exemplifies the potential of utilizing a DTC unit to construct an SMA for high-performance organic photovoltaics.