Unexpected solid–solid intermixing in a bilayer of poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acidmethyl ester via stamping transfer

The transferred bilayer active layer (P3HT/PCBM) prepared from a stamping transfer technique can be expected to undergo a sharp increase in the concentration profile at the P3HT/PCBM interface. However, the PCBM top layer is unexpectedly well blended with the P3HT bottom layer during the solid film stamping process with the help of the residual solvent. Auger spectroscopy confirmed that the bilayer have almost same composition from the anode side to the cathode side as the bulk-hetero junction film. This unique discovery can be applied in preparing concentration-graded BHJ film from controlling solid–solid intermixing behavior.