Host-Guest Strategy Enabling Nonhalogenated Solvent Processing for High-Performance All-Polymer Hosted Solar Cells

The power conversion efficiencies(PCEs)of all-polymer solar cells(all-PSCs),usually processed from low-boiling-point and toxic sol-vents,have reached high values of 18%.However,poor miscibility and uncontrollable crystallinity in polymer blends lead to a nota-ble drop in the PCEs when using green solvents,limiting the practical development of all-PSCs.Herein,a third component(guest)BTO was employed to optimize the miscibility and enhance the crystallinity of PM6/PY2Se-F host film processed from green solvent toluene(TL),which can effectively suppress the excessive aggregation of PY2Se-F and facilitate a nano-scale interpenetrating net-work morphology for exciton dissociation and charge transport.As a result,TL-processed all-polymer hosted solar cells(all-PHSCs)exhibited an impressive PCE of 17.01%.Moreover,the strong molecular interaction between the host and guest molecules also en-hances the thermal stability of the devices.Our host-guest strategy provides a unique approach to developing high-efficiency and stable all-PHSCs processed from green solvents,paving the way for the industrial development of all-PHSCs.

Host-Guest Active Layer Enabling Annealing-Free,Nonhalogenated Green Solvent Processing for High-Performance Organic Solar Cells

Recent advances in non-fullerene acceptors(NFAs)like Y6 have pushed the power conversion efficiencies(PCEs)of organic solar cells(OSCs)above 19%.However,the harsh fabrication conditions,such as the use of the highly volatile chloroform(CF)solvent and the thermal annealing process,are not suitable for large-area printing technologies and environmental standards.Here,a series of guest molecules,BT2O,BTO,and BT4O,are designed and synthesized with different numbers of oligo ethylene glycol(OEG)repeating units in side chains.All these guest molecules could tune the crystallization kinetics of the annealing-free host-guest active layers by inducing the self-assembly of Y6 in non-halogenated paraxylene(PX)solution.The increasing number of OEG repeating units in guest molecules could enhance the molecular assembly ability but molecular stacking steric hindrance simultaneously.Therefore,BTO with three OEG repeating units blended with PM6:PM7:Y6 delivers the highest PCE of 17.78%.Our results demonstrate controlling the crystallization kinetics via delicate side-chain engineering of guest molecules is an effective way to achieve efficient OSCs in non-halogenated solution.