Solid additive enables efficient and stable organic solar cells by stabilizing morphology of active layer

Abstract

Additive strategy is an effective method for optimizing the morphology of active layer in organic solar cells (OSCs). However, common high boiling points solvent additives may compromise device stability. In this work, 1-bromo-8-chloronaphthalene (BCN) was used as a solid additive to improve device performance. The introduction of BCN promotes the crystallinity, H-aggregation and fibrillation of L8-BO. The active layer film with additive BCN exhibits optimized phase separation and refined fiber network, thus enhancing the exciton dissociation and charge transport in the corresponding devices. Compared with control devices (without additives), the power conversion efficiency (PCE) of optimized devices (with 20 wt % BCN) based on D18:L8-BO was increased from 17.49 % to 18.20 %. The detailed process of device fabrication is in experimental section. Furthermore, devices processed by BCN preserved 96.6 % and 96.3 % of the initial PCE after aging for 60 min with maximum power point (MPP) tracking and aging of storage for 960 h, respectively. The universality of BCN was verified in different systems, which offers promising opportunities to regulate BHJ morphology toward highly efficient OSCs.