X-ray photoelectron spectroscopy reveals CH3 bonding sites in CH3NH3PbBr3 thin films upon methyl lead modification

Methylammonium lead halide perovskite (MAPbX 3 ) has been a great candidate for photovoltaic applications. However, dissociation of the methylammonium unit has been observed, producing a CH 3 – group binding to MAPbX 3 and a free NH 3 molecule. To date, there is no clear evidence on the specific binding site of CH 3 –. In this study, MAPbBr 3 thin films are prepared with deliberately added trimethyl lead bromide, (CH 3 ) 3 PbBr. X-ray photoelectron spectroscopy is applied to comparatively investigate the electronic structure of MAPbBr 3 films with and without (CH 3 ) 3 PbBr modification. CH 3 -Pb species are identified, confirming that Pb is a binding site for CH 3 produced upon MA dissociation. Graphical abstract