All‐polymer solar cells (all‐PSCs) have drawn growing attention and achieved tremendous progress recently, but their power conversion efficiency (PCE) still lags behind small‐molecule‐acceptor (SMA)‐based PSCs due to the relative difficulty on morphology control of polymer photoactive blends. Here, low‐cost PTQ10 is introduced as a second polymer donor (a third component) into the PM6:PY‐IT blend to finely tune the energy‐level matching and microscopic morphology of the polymer blend photoactive layer. The addition of PTQ10 decreases the π–π stacking distance, and increases the π–π stacking coherence length and the ordered face‐on molecular packing orientation, which improves the charge separation and transport in the photoactive layer. Moreover, the deeper highest occupied molecular orbital energy level of the PTQ10 polymer donor than PM6 leads to higher open‐circuit voltage of the ternary all‐PSCs. As a result, a PCE of 16.52% is achieved for ternary all‐PSCs, which is one of the highest PCEs for all‐PSCs. In addition, the ternary devices exhibit a high tolerance of the photoactive layer thickness with high PCEs of 15.27% and 13.91% at photoactive layer thickness of ≈205 and ≈306 nm, respectively, which are the highest PCEs so far for all‐PSCs with a thick photoactive layer.
High efficiency organic solar cells (OSCs) based on A-DA'D-A type small molecule acceptors (SMAs) were mostly fabricated by toxic halogenated solvent processing, and power conversion efficiency (PCE) of the nonhalogenated solvent processed OSCs is mainly restricted by the excessive aggregation of the SMAs. To address this issue, we developed two vinyl π-spacer linking-site isomerized giant molecule acceptors (GMAs) with the π-spacer linking on the inner carbon (EV-i) or out carbon (EV-o) of benzene end group of the SMA with longer alkyl side chains (ECOD) for the capability of non-halogenated solvent-processing. Interestingly, EV-i possesses a twisted molecular structure but enhanced conjugation, while EV-o shows a better planar molecular structure but weakened conjugation. The OSC with EV-i as acceptor processed by the non-halogenated solvent o-xylene (o-XY) demonstrated a higher PCE of 18.27 % than that of the devices based on the acceptor of ECOD (16.40 %) or EV-o (2.50 %). 18.27 % is one of the highest PCEs among the OSCs fabricated from non-halogenated solvents so far, benefitted from the suitable twisted structure, stronger absorbance and high charge carrier mobility of EV-i. The results indicate that the GMAs with suitable linking site would be the excellent candidates for fabricating high performance OSCs processed by non-halogenated solvents.
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