Low-Volatility Fused-Ring Solid Additive Engineering for Synergistically Elongating Exciton Lifetime and Mitigating Trap Density Toward Organic Solar Cells of 20.5% Efficiency

Amphiphilic Additives Enable the Preparation of Efficient Organic Photovoltaics by Spontaneous Spreading Process

The spontaneous spreading (SS) process is one of the solution-processed technologies for preparing organic photovoltaics (OPVs). As a broadly used solvent in OPV preparation, chloroform is rarely applied in the SS process since the chloroform-based active layer solution generally forms a wrinkled film, which limits the performance of the devices. In this work, an SS process is developed with amphiphilic additives to prepare efficient OPVs using chloroform as the solvent. By adding amphiphilic additives into the chloroform solution, the interfacial tension between the chloroform solution and water can be tuned finely, and a uniform active layer film can be formed on the water surface. Adopting SS-PM6:Y6 film as the active layer, the SS-OPV is successfully prepared in open-air conditions, and the device performance is comparable to the device prepared by the spin-coating method. Notably, the OPV device using recycled SS-PM6:Y6 film is also demonstrated to present an efficiency of over 14%.

4-Iodobenzonitrile as Effective Solid Additive for High-Efficiency Polymer Solar Cells

Solid additive engineering is a well-established and effective strategy for enhancing active layer morphology in polymer solar cells (PSCs), thereby improving their power conversion efficiency (PCE). However, the availability of effective solid additive molecules remains limited, especially those combining simple structural units with a large dipole moment to promote strong interactions with active materials. In this study, we introduce 4-iodobenzonitrile (IBZN), a commercially available, low-cost, and structurally simple molecule with a high dipole moment (3.33 debye), as a solid additive for PSCs. Theoretical calculations, ultraviolet-visible (UV-Vis) spectroscopy experiments, and a morphology analysis demonstrate that IBZN forms strong interactions with L8-BO, subsequently enhancing the packing mode and crystallization. The incorporation of IBZN into PM6:L8-BO-based PSCs resulted in an increased fill factor (FF) of 79.54% and a boosted PCE from 17.49% to 18.77%. Furthermore, IBZN has also demonstrated outstanding regulatory effects in systems based on other Y-series acceptors, such as Y6 and BTP-ec9. This study not only introduces a structurally simple solid additive molecule characterized by a large dipole moment but also offers valuable insights for the subsequent development of novel solid additives aimed at enhancing the morphology and efficiency of PSCs.