Ternary organic solar cells (OSCs) provide a convenient and effective means to further improve the power conversion efficiency (PCE) of binary ones via composition control. However, the role of the third component remains to be explored in specific binary systems. Herein, we report ternary blend solar cells by adding the narrow-band-gap donor PCE10 as the mediator into the PBDB-T:IDTT-T binary blend system. The extended absorption, efficient fluorescence resonance energy transfer, enhanced charge dissociation, and induced tighter molecular packing of the ternary blend films enhance the photovoltaic properties of devices and deliver a champion PCE of 10.73% with an impressively high open-circuit voltage (V OC) of 1.03 V. Good miscibility and similar molecular packing behavior of the components guarantee the desired morphology in the ternary blend films, leading to solar cell devices with over 10% PCEs at a range of compositions. Our results suggest that ternary systems with properly aligned energy levels and overlapping absorption among the components hold great promises to further enhance the performance of corresponding binary ones.

Advances in small-molecule non-fullerene acceptors have led to increase in power conversion efficiencies (PCEs) of organic solar cells. Simultaneously, small molecules feature lower viscosity and better crystallization properties, which makes it easier to manipulate the molecular packing, film morphology, and device performance during the fabrication process. In this contribution, we fabricate all-small molecule solar cells based on BTR:Y6 with sequential annealing, and an enhanced PCE of 11.88% is achieved with J SC of 22.60 mA cm–2, V OC of 0.837 V, and FF of 62.79%. The morphological study reveals the concomitant of third-order lamellar and π-π stacking peaks and the improved BTR crystallite, indicating the improved crystallization properties. At the same time, the favorable film morphology with an interpenetrated network structure is also formed in blend films with sequential annealing. Thus, bimolecular and trap-assisted recombination can be effectively suppressed in the optimal solar cell devices. Such studies underline the significance of morphology control in fabricating highly efficient small-molecule solar cells.

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In the past decade, three-dimensional (3D) perovskites have been under intense study. However, these devices always suffer from severe performance degradation. Recently, two-dimensional (2D) perovskites have attracted increasing attention due to their excellent environmental stability, but their low power conversion efficiency (PCE) limits their application. Therefore, many strategies have been applied to manipulate the crystallization and suppress the defects and low-n value phases. Additive engineering, as one of the most effective methods to achieve the above-mentioned goals, has been extensively studied. In this contribution, thiourea (TU) and methylammonium chloride (MACl) are successfully employed to contribute synergistically to optimize the crystallization process, leading to an enlarged grain size, smooth and dense surface morphology, and suppressed distribution of n values for improved phase purity. As a result, the optimized inverted Dion−Jacobson (DJ) 2D perovskite solar cell (PSC) device delivers an elevated PCE of 12.16% with a significantly improved short-circuit current density (J SC ) of 18.78 mA cm −2 and fill factor (FF) of 62.70%. In addition, the optimized devices show good environmental stability when exposed to ambient air.

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