Small‐molecule acceptors (SMAs)‐based organic solar cells (OSCs) have exhibited great potential for achieving high power conversion efficiencies (PCEs). Meanwhile, developing asymmetric SMAs to improve photovoltaic performance by modulating energy level distribution and morphology has drawn lots of attention. In this work, based on the high‐performance SMA (Y6), three asymmetric SMAs are developed by substituting the fluorine atoms on the terminal group with chlorine atoms, namely SY1 (two F atoms and one Cl atom), SY2 (two F atoms and two Cl atoms), and SY3 (three Cl atoms). Y6 (four F atoms) and Y6‐4Cl (four Cl atoms) are synthesized as control molecules. As a result, SY1 exhibits the shallowest lowest unoccupied molecular orbital energy level and the best molecular packing among these five acceptors. Consequently, OSCs based on PM6:SY1 yield a champion PCE of 16.83% with an open‐circuit voltage (VOC) of 0.871 V, and a fill factor (FF) of 0.760, which is the best result among the five devices. The highest FF for the PM6:SY1‐based device is mainly ascribed to the most balanced charge transport and optimal morphology. This contribution provides deeper understanding of applying asymmetric molecule design method to further promote PCEs of OSCs.

Symmetric conjugated molecules can be broken through suitable synthetic strategies to construct novel asymmetric molecules, which can largely broaden the material library. In the field of organic solar cells, fused‐ring electron acceptors (FREAs) with the A‐DA'D‐A type backbone structure have attracted much attention and enabled power conversion efficiencies (PCE) exceeding 18%. Among them, Y6 is one of the most classic FREAs that can derive many symmetric and asymmetric molecules and exhibit unique optoelectronic properties. Thus, in this review, the focus is on the recent progress of Y6‐derived asymmetric FREAs containing a dipyrrolobenzothiadiazole segment, which can be classified as the following three categories: asymmetric end group, asymmetric central core and asymmetric side chain. The relationship of the molecular structure, optoelectronic properties, and device performance is discussed in detail. Finally, the future design directions and challenges faced by this kind of photovoltaic materials are given.

High-efficiency organic solar cells (OSCs) can be produced through optimization of component molecular design, coupled with interfacial engineering and control of active layer morphology. However, vertical stratification of the bulk-heterojunction (BHJ), a spontaneous activity that occurs during the drying process, remains an intricate problem yet to be solved. Routes toward regulating the vertical separation profile and evaluating the effects on the final device should be explored to further enhance the performance of OSCs. Herein, we establish a connection between the material surface energy, absorption, and vertical stratification, which can then be linked to photovoltaic conversion characteristics. Through assessing the performance of temporary, artificial vertically stratified layers created by the sequential casting of the individual components to form a multilayered structure, optimal vertical stratification can be achieved. Adjusting the surface energy offset between the substrate results in donor and acceptor stabilization of that stratified layer. Further, a trade-off between the photocurrent generated in the visible region and the amount of donor or acceptor in close proximity to the electrode was observed. Modification of the substrate surface energy was achieved using self-assembled small molecules (SASM), which, in turn, directly impacted the polymer donor to acceptor ratio at the interface. Using three different donor polymers in conjunction with two alternative acceptors in an inverted organic solar cell architecture, the concentration of polymer donor molecules at the ITO (indium tin oxide)/BHJ interface could be increased relative to the acceptor. Appropriate selection of SASM facilitated a synchronized enhancement in external quantum efficiency and power conversion efficiencies over 10.5%.

Acquiring precision adjustable morphology of the blend films to improve the efficiency of charge separation and collection is a constant goal of organic solar cells (OSCs). Here, the above problem is improved by synergistically combining the sequential deposition (SD) method and the additive general strategy. By adding one additive 1,10‐decanediol (DDO) into PM6 and another 1‐chloronaphthalene (CN) into Y6, the molecule orientation of PM6 and the crystallite texture of the Y6 all become order. During the SD processing, a vertical phase separation OSCs device is formed where the donor enrichment at the anode and acceptor enrichment at the cathode. In comparison, the SD OSCs device with only CN additive still displays the bulk‐heterojunction morphology similar to PM6:Y6 blend film. The morphology with vertical phase distribution can not only inhibit charge recombination but also facilitate charge collection, finally enhancing the fill factor (FF) and photocurrent in binary additives SD‐type OSCs. As a result, the binary additives SD‐type OSCs with blend film PM6+DDO/Y6+CN exhibit a high FF of 77.45%, enabling a power conversion efficiency as high as 16.93%. This work reveals a simple but effective approach for boosting high‐efficiency OSCs with ideal morphologies and demonstrates that the additive is a promising processing alternative.