Surface analytical investigation on organometal triiodide perovskite

"Surface analytical investigation on organometal triiodide perovskite" (2015). In a little over a year, there has been an unexpected breakthrough and rapid evolution of highly efficient solid-state hybrid solar cells based on organometal trihalide perovskite materials. This technology has the potential to produce solar cells with the very highest efficiencies while retaining the very lowest cost. The authors have measured the electronic density of states of CH 3 NH 3 PbI 3 using ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and x-ray photoemission spectroscopy (XPS). The valence band maximum and conduction band minimum positions are obtained from the UPS and IPES spectra, respectively, by linear extrapola-tion of the leading edges. The authors investigate the Au/perovskite and C 60 /perovskite interfaces by UPS and XPS. An interface dipole of 0.1 eV is observed at Au/perovskite interface. The energy levels of perovskite shift upward by ca.0.4 eV with Au coverage of 64 A ˚ upon it, resulting in band bending, hence a built-in field in perovskite that encourages hole transport to the interface. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskite film to fullerene molecules. Further dep-osition of fullerene forms C 60 solid, accompanied by the reduction of the electron transfer. The strongest electron transfer happened at 1/4 monolayer of fullerene. V C 2015 American Vacuum Society.