1：Experimental Design and Method Selection:

The study involved the systematic design, synthesis, and characterization of three organic dopant-free X-shaped molecules (D31, D32, and D33) for fabricating p-i-n perovskite solar cells. The X-shaped design is based on a benzene core unit with four arms attached, two of which are triphenylamines and two are azomethine bridges connected to functionalized phenyl rings (-H, -OCH3, -CN).

2：Sample Selection and Data Sources:

The materials were synthesized starting with the 2,5-dibromoterephthalaldehyde, which is synthesized from 1,4-dibromobenzene. The methoxy-substituted triphenylamine and substituted aniline are incorporated with benzene core through Suzuki coupling and Schiff based condensation chemistry.

3：List of Experimental Equipment and Materials:

The study utilized UV-vis absorption spectra, cyclic voltammetry (CV), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and scanning electron microscopy (SEM) for characterization.

4：Experimental Procedures and Operational Workflow:

The final products were purified in a simple washing and crystallization procedures. The photovoltaic performance of the devices was measured under simulated AM 1.5 G irradiation (100 mW cm-2).

5：5 G irradiation (100 mW cm-2). Data Analysis Methods:

5. Data Analysis Methods: The hole mobilities of D31, D32, and D33 were performed using hole-only devices with the configuration of ITO/PEDOT:PSS/HTMs/Au, which were estimated with space charge limited current (SCLC) method.