Morphology control in laboratory and industry setting remains as a major challenge for organic solar cells (OSCs) due to the difference in film-drying kinetics between spin coating and the printing process. A two-step sequential deposition method is developed to control the active layer morphology. A conjugated polymer that self-assembles into a well-defined fibril structure is used as the first layer, and then a non-fullerene acceptor is introduced into the fibril mesh as the second layer to form an optimal morphology. A benefit of the combined fibril network morphology and non-fullerene acceptor properties was that a high efficiency of 16.5% (certified as 16.1%) was achieved. The preformed fibril network layer and the sequentially deposited non-fullerene acceptor form a robust morphology that is insensitive to the polymer batches, solving a notorious issue in OSCs. Such progress demonstrates that the utilization of polymer fibril networks in a sequential deposition process is a promising approach towards the fabrication of high-efficiency OSCs.

Ternary structure has been demonstrated as an effective strategy to realize high power conversion efficiency (PCE) in organic solar cells (OSCs), however general materials selection rules still remain incompletely understood. In this work, two non-fullerene small molecule acceptors 3TP3T-4F and 3TP3T-IC are synthesized and incorporated as the third component in the PM6:Y6 binary blends. The photovoltaic behaviors in the resultant ternary OSCs differ significantly, despite the comparable energy levels. We found that incorporation of 15% 3TP3T-4F into the PM6:Y6 blend results in facilitating exciton dissociation, increasing charge transport and reducing trap-assisted recombination. All these features are

In non-fullerene organic solar cells, the long-range structure ordering induced by end-group π–π stacking of fused-ring non-fullerene acceptors is considered as the critical factor in realizing efficient charge transport and high power conversion efficiency. Here, we demonstrate that side-chain engineering of non-fullerene acceptors could drive the fused-ring backbone assembly from a π–π stacking mode to an intermixed packing mode, and to a non-stacking mode to refine its solid-state properties. Different from the above-mentioned understanding, we find that close atom contacts in a non-stacking mode can form efficient charge transport pathway through close side atom interactions. The intermixed solid-state packing motif in active layers could enable organic solar cells with superior efficiency and reduced non-radiative recombination loss compared with devices based on molecules with the classic end-group π–π stacking mode. Our observations open a new avenue in material design that endows better photovoltaic performance.

At present, most of the top-performing organic solar cells (OSCs) are processed with high boiling point solvent additives, which usually have a negative effect on the device stability. To overcome...

The development of high-performance donor polymers is important for obtaining high power conversion efficiencies (PCEs) of non-fullerene polymer solar cells (PSCs). Currently, most high-efficiency PSCs are fabricated with benzo[1,2-b:4,5-b′]dithiophene (BDT)-based conjugated polymers. The photovoltaic performance of benzo[1,2-b:4,5-b′]difuran (BDF)-based copolymers has lagged far behind that of BDT-based counterparts. In this study, a novel BDF-based copolymer L2 is designed and synthesized, in which BDF and benzotriazole (BTz) building blocks have been used as the electron-sufficient and deficient units, respectively. When blending with a non-fullerene small molecule acceptor (SMA), TTPT-T-4F, the L2-based device exhibits a remarkably high PCE of 14.0%, which is higher than that of the device fabricated by its analogue BDT copolymer (12.72%). Moreover, PSCs based on the L2:TTPT-T-4F blend demonstrate excellent ambient stability with 92% of its original PCE remaining after storage in air for 1800 h. Thus, BDF is a promising electrondonating unit, and the BDF-based copolymers can be competitive or even surpass the performance of BDT-based counterparts.