Experimental Determination of Atomic Scale Structure and Energy-Level Alignment of C₆₀ on CsPbBr₃(001)

The efficiency and stability of perovskite solar cells are largely determined by the interfaces between different functional layers in the device. Here, we investigate the atomic scale structural and electronic properties of C 60 on thin films of CsPbBr 3 on Au(001) by scanning tunneling microscopy and spectroscopy (STM/STS). By varying the PbBr 2 content of the film, we control the surface termination, switching between CsBr and PbBr 2, with each exhibiting distinct reconstructions. Investigating the self-assembly of C 60 in the submonolayer regime, we find that the molecule–substrate interaction is enhanced on the PbBr 2 -terminated perovskite film. By STS, we determine the electronic energy-level alignment of the C 60 frontier orbitals, revealing that regardless of surface termination, a C 60 film functions as an electron transport layer in a device. However, different surface terminations induce a significant shift in the molecular energy levels by 0.4 eV, with implications for electron mobility and recombination losses in applications.