fig4

Figure 4. (A) In 3d XPS spectra of SAM-modified ITO substrates. (B) UPS spectra of the SAM substrates and the corresponding perovskite films. (C) Energy level alignment diagram of the SAM/perovskite interface. (D) Steady-state PL spectra of perovskite films deposited on different SAM substrates. (E) TRPL spectra of perovskite films on different SAM substrates. (F) Dark I-V characteristics of hole-only devices. 3-FPy: 3-fluoropyridine; 3-MeOPy: 3-methoxypyridine; HOMO: highest occupied molecular orbital; WF: work function; XPS: X-ray photoelectron spectroscopy; SAM: self-assembled monolayer; ITO: indium tin oxide; UPS: ultraviolet photoelectron spectroscopy; PL: photoluminescence; TRPL: time-resolved photoluminescence; I-V: current–voltage.