Aggregation Optimization of Cathode Interlayer via Incorporating Cellulose Enables High-Performance Organic Solar Cells

Regulating aggregation and molecular packing of small-molecule cathode interlayer (CIL) materials is a significant but imperceptible issue in the development of high-performance organic solar cells (OSCs). For the celebrity PDINN small molecule, the strong aggregation tendency of the perylene diimide molecular backbone leads to excessive crystallinity when films form, ultimately affecting the morphology and charge transport ability of the films. Herein, we address this issue by developing a hydroxyl-induced anti-aggregation strategy by introducing a suitable amount of hydroxypropyl cellulose (HPC) into the solution of PDINN, and a careful balance is achieved between the film-forming quality and the aggregation of the material. Taking two commercially available active layer systems, PM6/Y6 and D18/L8-BO, as examples, the introduction of HPC significantly increases the J_SC and FF values of the devices. Therefore, power conversion efficiency risen from 17.38% to 18.25% for the PM6/Y6 system and from 18.45% to 19.73% for the D18/L8-BO system, and it was proved that the thickness tolerance of the HPC hybrid interface was improved significantly. This hydroxyl-induced anti-aggregation strategy has demonstrated efficiency in other active layer systems. This work provides a simple and effective method to solve the aggregation problem of small molecule CIL materials, which is conducive to the commercial development of OSCs.