*2.3. Measurements*

X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were conducted for the perovskite samples using the D8 Advance X-ray diffractometer (Bruker, Billerica, MA, USA) and the K-Alpha X-ray photoelectron spectrometer (Thermo Electron, Waltham, MA, USA), respectively.

Current density–voltage (J–V) curves of the PSCs were obtained using the 2400 Series *J*–*V* Source Meter (Keithley Instrument, Solon, OH, USA) under an irradiation intensity of 100 mW cm<sup>2</sup> (AM1.5). We used a solar simulator (XES-301S, SAN-EI ELECTRIC, Osaka, Japan) for simulating sunlight irradiation.

The space charge limited current (SCLC) of a hole-only device (glass/ITO/PTAA/ Perovskite/PTAA/Ag) was obtained using the Keithley 2400 Source Meter under dark conditions. Electrochemical impedance spectroscopy (EIS) of the PSCs was performed with an electrochemical work station (CH instruments, Austin, TX, USA) under dark conditions. Steady-state photoluminescence (PL) spectroscopy was conducted using FLS920 (Edinburgh Instruments, Livingston, UK) at wavelengths between 720 nm and 800 nm with the excitation wavelength of 514 nm. Ultraviolet–visible absorption spectroscopy was performed with a UV–vis-NIR 3600 spectrometer (Shimadzu, Kyoto, Japan). The morphology of the devices was measured by the scanning electron microscope (SEM, JOEL, Tokyo, Japan) and atomic force microscope (AFM, Veeco, Plainview, NY, USA).
