The performance of organic solar cells has been dramatically enhanced due to the use of bulk heterojunction active layer structure. However, blending donor and acceptor in the bulk volume results in a large extent of bimolecular charge recombination and increasing energetic disorder. Herein, we fabricated organic solar cells with polymer donor PM6 and nonfullerene acceptor N3 in bilayer structure to investigate the impact of planar heterojunction configurations on charge recombination and energetic landscapes. We find superior crystallinity features in the bilayer composed of pure donor and acceptor layers. The bimolecular charge recombination and energetic disorder are effectively suppressed compared with the bulk heterojunction counterparts. Thus, a power conversion efficiency as high as 18.1% (17.8% averaged) is achieved, which stands among the top values of planar heterojunction organic solar cells. In addition, improved device shelf stability is observed because of the fewer donor–acceptor interfaces in the active layer. Our results suggest that a planar heterojunction structure could efficiently suppress the bimolecular charge recombination and energetic disorder, providing an alternative pathway for developing solution-processed organic solar cells.

Organic photodiodes (OPDs) have emerged as a potential alternative for inorganic photodiodes in light-detection technology due to the unique properties such as light weight, flexibility, and tunable absorption range. However,...

The sequential deposition method assists the vertical phase distribution in the photoactive layer of organic solar cells, enhancing power conversion efficiencies. With this film coating approach, the morphology of both layers can be fine‐tuned with high boiling solvent additives, as frequently applied in one‐step casting films. However, introducing liquid additives can compromise the morphological stability of the devices due to the solvent residuals. Herein, 1,3,5‐tribromobenzene (TBB) with high volatility and low cost, is used as a solid additive in the acceptor solution and combined thermal annealing to regulate the vertical phase in organic solar cells composed of D18‐Cl/L8‐BO. Compared to the control cells, the devices treated with TBB and those that underwent additional thermal processing exhibit increased exciton generation rate, charge carrier mobility, charge carrier lifetime, and reduced bimolecular charge recombination. As a result, the TBB‐treated organic solar cells achieve a champion power conversion efficiency of 18.5% (18.1% averaged), one of the highest efficiencies in binary organic solar cells with open circuit voltage exceeding 900 mV. This study ascribes the advanced device performance to the gradient‐distributed donor‐acceptor concentrations in the vertical direction. The findings provide guidelines for optimizing the morphology of the sequentially deposited top layer to achieve high‐performance organic solar cells.

The cathode interlayer plays a vital role in organic solar cells, which can modify the work function of electrodes, lower the electron extraction barriers, smooth the surface of the active layer, and remove solvent residuals. However, the development of organic cathode interlayer lags behind the rapidly improved organic solar cells because their intrinsic high surface tension can lead to poor contact with the active layers. Herein, a double‐dipole strategy is proposed to enhance the properties of organic cathode interlayers, which is induced by incorporating nitrogen‐ and bromine‐containing interlayer materials. To verify this approach, the state‐of‐the‐art active layer composed of PM6:Y6 and two prototypical cathode interlayer materials, PDIN and PFN‐Br is selected. Using the cathode interlayer PDIN: PFN‐Br (0.9:0.1, in wt.%) in the devices can reduce the electrode work function, suppress the dark current leakage, and improve charge extractions, leading to enhanced short circuit current density and fill factor. The bromine ions tend to break from PFN‐Br and form a new chemical bond with the silver electrode, which can adsorb extra dipoles directed from the interlayer to silver. These findings on the double‐dipole strategy provide insights into the hybrid cathode interlayers for efficient non‐fullerene organic solar cells.