The emergence of polymerized small molecule acceptors (PSMAs) has significantly improved the performance of all-polymer solar cells (all-PSCs). However, the pace of device engineering lacks behind that of materials development, so that a majority of the PSMAs have not fulfilled their potentials. Furthermore, most high-performance all-PSCs rely on the use of chloroform as the processing solvent. For instance, the recent high-performance PSMA, named PJ1-γ, with high LUMO, and HOMO levels, could only achieve a PCE of 16.1% with a high-energy-level donor (JD40) using chloroform. Herein, we present a methodology combining sequential processing (SqP) with the addition of 0.5%wt PC₇₁BM as a solid additive (SA) to achieve an impressive efficiency of 18.0% for all-PSCs processed from toluene, an aromatic hydrocarbon solvent. Compared to the conventional blend-casting (BC) method whose best efficiency (16.7%) could only be achieved using chloroform, the SqP method significantly boosted the device efficiency using toluene as the processing solvent. In addition, the donor we employ is the classic PM6 that has deeper energy levels than JD40, which provides low energy loss for the device. We compare the results with another PSMA (PYF-T-o) with the same method. Finally, an improved photostability of the SqP devices with the incorporation of SA is demonstrated.

Most of the recent organic solar cells (OSCs) with top-of-the-line efficiencies are processed from organic solvents with a high vapor pressure such as CF in nitrogen-filled glovebox, which is not feasible for large-area manufacturing. Herein, we cast active layers with both aromatic hydrocarbon solvents and halogenated solvents without any solvent additive or post-treatment, as well as interlayers with water and methanol in air (35% relative humidity) for efficient OSCs, except cathode electrode’s evaporation is in vacuum. Compared to the PM6:Y6 system that is processed from CF, the PM6:BTP-ClBr2 system demonstrates good efficiency of 16.28% processed from CB and the device based on PM6:BTP-4Cl achieves 16.33% using TMB as its solvent for the active layer. These are among the highest efficiencies for CB- and TMB-processed binary OSCs to date. The molecular packing and phase separation length scales of each combination depend strongly on the solvent, and the overall morphology is the result of the interplay between solvent evaporation (kinetics) and materials miscibility (thermodynamics). Different solvents are required to realize the optimal morphology due to the different miscibility between the donor and acceptor. Finally, 17.36% efficiency was achieved by incorporating PC₇₁BM for TMB-processed devices. Our result provides insights into the effect of processing solvent and shows the potential of realizing high-performance OSCs in conditions relevant for industrial fabrication.