Supplementary Figure 1, Supplementary Figure 2, Supplementary Figure 3, Supplementary Table 1

See the supplementary material for UPS data measured using low-energy photon light (7.7 and 3.8 eV). Supplementary Figure 1 shows the UPS spectra of ITO measured with 7.7 eV photon energy before and after exposure to a helium discharge lamp. Supplementary Figure 2 presents the UPS spectra of bare ITO and aluminum deposited on ITO with 7.7 eV photon energy. Supplementary Figure 3 compares the UPS spectra of BPhen deposited on Al with different substrates-ITO and HOPG-measured using 3.8 eV light. Supplementary Table 1 lists the QEs of various photocathodes reported in previous studies, including that of p-Pyrrd-Phen in this study.