1：Experimental Design and Method Selection:

The study involved synthesizing three D–π–A organic dyes with indolo[3,2-b]indole as the donor and different π-spacers (benzene, thiophene, furan) linked to a cyanoacrylic acid acceptor. Methods included one-pot MCR/oxidation, Suzuki coupling, and Knoevenagel condensation for synthesis; UV-Vis spectroscopy, cyclic voltammetry, DFT calculations for characterization; and device fabrication with TiO2 electrodes, Pt counter electrodes, and I?/I?? electrolyte for photovoltaic testing.

2：Sample Selection and Data Sources:

Dyes IID-1, IID-2, IID-3 were synthesized and characterized. Devices were fabricated using FTO-coated glass substrates, TiO2 paste, and standard electrolyte. Data were collected from spectroscopic, electrochemical, and photovoltaic measurements.

3：List of Experimental Equipment and Materials:

Equipment included Bruker AMX 500 spectrophotometer for NMR, Thermo Scientific Exactive mass spectrometer for HRMS, Bruker FT-IR spectrometer, Buchi melting point apparatus, Newport Class AAA solar simulator Sol3A-94023 for J-V measurements, Autolab PGSTAT 302N for electrochemical measurements. Materials included chemicals like cyclohexanone, n-hexylamine, boronic acids, cyanoacetic acid, TiO2 paste, Pt paste, Surlyn spacer, and electrolytes.

4：Experimental Procedures and Operational Workflow:

Synthesis involved sequential reactions: MCR-oxidation to form indoloindole, N-alkylation, Suzuki coupling with formyl-aryl/heteroaryl boronic acids, and Knoevenagel condensation. Device fabrication included cleaning FTO, coating TiO2, dye sensitization, assembling cells with electrolyte, and measuring J-V characteristics, IPCE, OCVD, IMVS, EIS.

5：Data Analysis Methods:

Data were analyzed using Gaussian 09 for DFT calculations, fitting routines for EIS data, and standard equations for lifetime calculations from OCVD and IMVS.