1：Experimental Design and Method Selection:

The study prepared P3HT/PC61BM bilayer interdiffusion heterojunction organic solar cells using orthogonal solvent method. The charge transport and extraction characteristics were investigated through transient photovoltage/transient photocurrent measurements and photo-induced charge carrier extraction by linearly increasing voltage technology.

2：Sample Selection and Data Sources:

The electron donor material P3HT and electron acceptor material PC61BM were used. Devices were fabricated on ITO-coated glass substrates with PEDOT:PSS as hole-conducting material.

3：List of Experimental Equipment and Materials:

Instruments included a Bruker Stylus Profile for thickness measurement, ultraviolet–visible spectrophotometer, fluorescence spectrometer, X-ray diffractometer, Keithley2400 source meter unit, AM 1.5 solar simulator, and Paios system for Photo-CELIV, TPC, and TPV measurements.

4：5 solar simulator, and Paios system for Photo-CELIV, TPC, and TPV measurements. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The devices were fabricated by spin-coating P3HT and PC61BM solutions sequentially on ITO substrates, followed by thermal annealing and aluminum electrode deposition.

5：Data Analysis Methods:

Data analysis involved measuring UV-Vis absorption spectra, PL spectra, XRD patterns, J-V characteristics, EQE spectra, and analyzing charge recombination dynamics and charge extraction processes.