1,8,9‐Trihydroxyanthracene as a Green Solid Additive for Operational Stability in Organic Solar Cells

A novel green solid additive, 1,8,9‐Trihydroxyanthracene (TOHA), is demonstrated to effectively improve both efficiency and stability of a highly efficient organic solar cell (OSC), comprising D18‐Cl as polymer donor and N3 as small‐molecule acceptor. The D18‐Cl:N3 device achieves an elevated power conversion efficiency of 17.91%, compared to 17.15% of that processed without TOHA. The enhanced performance is attributed to the addition of TOHA, leading to more refined phase separation and stronger molecular packing in D18‐Cl:N3 blend films, and improves the charge generation, exciton dissociation, charge transport, and collection, which contribute to higher photocurrent and fill factor for D18‐Cl:N3 OSCs. Meanwhile, TOHA‐treated D18‐Cl:N3 induces lower Δ E loss . Remarkably, it can simultaneously enhance the operational stability, with the TOHA‐treated OSC maintaining 68% of the initial efficiency after 1400 h operation. Morphology measurement (atomic force microscopy, 2D grazing‐incidence wide‐angle X‐ray scattering, and time‐of‐flight–secondary‐ion mass spectrometry) also illustrates that TOHA improves the stability of the film with smaller Urban energy value of device after aging. TOHA‐treated D18‐Cl:N3 cell after aging shows smaller reduction on exciton dissociation, charge transport, charge collection, and nonradiative recombination. This work demonstrates the significance of processing condition‐controlled additive pathways for the realization of stability, leading to superior OSC devices.