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 ΔE_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.