Electronic structure and chemical reaction of Ca deposition on resiore8ular poly（3-hexylthiophene） surfaces

Conjugated polymer, regioregular poly（3-hexylthiophene） （rr-P3HT）, films were prepared by spin-coating the rr-P3HT chloroform solution onto clean silicon wafer surfaces. The chemical re- action and electronic structure of Ca deposition on rr-P3HT surfaces were in situ investigated by synchrotron radiation photoemission spectroscopy （SRPES） and X-ray photoemission spectros- copy （XPS）. Upon Ca deposition, Ca-induced band bending of rr-P3HT is observed. In addition, Ca atoms preferentially react with S atoms of rr-P3HT. No obvious reaction between Ca and C atoms can be found. Through the investigation of the evolution of valence band spectra and secondary electron cut-off of rr-P3HT during the process of Ca deposition, an energy level alignment diagram at the Ca/rr-P3HT interface is derived.