1：Experimental Design and Method Selection

The study employed a facile synthetic strategy to introduce electron-deficient-core-based fused structures into non-fullerene acceptors (Y1 and Y2). The optoelectronic properties were delicately tuned to achieve efficient charge separation and small voltage losses. The devices were fabricated with an inverted structure of ITO/ZnO/active layer/MoO3/Ag.

2：Sample Selection and Data Sources

Two non-fullerene acceptor molecules (Y1 and Y2) were synthesized and blended with the commercial donor polymer PBDB-T. The active layers were optimized for donor/acceptor ratios.

3：List of Experimental Equipment and Materials

UV-Vis absorption spectra were recorded on the SHIMADZU UV-4100 spectrophotometer. Cyclic voltammetry measurements were performed using a CHI 660E electrochemical workstation. Photoluminescence and electroluminescence spectra were measured using a light guide positioned close to the sample. Atomic force microscopy (Bruker Dimension Fast Scan Scanning Probe Microscope) and transmission electron microscopy (T12 cryo-electron microscope) were used for morphology investigation. Grazing incidence wide-angle X-ray scattering (GIWAXS) measurements were performed at Advanced Light Source, Lawrence Berkeley National Laboratory.

4：Experimental Procedures and Operational Workflow

The ITO glass was precleaned and treated in an ultraviolet–ozone chamber. A thin layer of ZnO was spin-coated onto the ITO glass. The polymer PBDB-T:Y1 or Y2 blends were spin-cast onto the ZnO layer. A bilayer cathode consisting of MoO3 capped with Ag was thermal evaporated under a shadow mask. The J–V characteristics of photovoltaic cells were taken using a Keithley 2400 source measure unit under a simulated AM 1.5 G spectrum.

5：Data Analysis Methods

The optical gaps were determined from the intersection between normalized emission and absorption spectra. The mobilities were obtained by fitting the current–voltage curves to a space charge limited form. The voltage losses were evaluated by investigating the electroluminescence quantum efficiency and photoluminescence quenching for the blend films.