Charge-transfer states in poly(3-hexylthiophene-2,5-diyl) induced by chemical interaction with molybdenum trioxide

Charge transfer at the interface between poly(3-hexylthiophene-2,5-diyl) (P3HT) and molybdenum trioxide (MoO₃) was investigated by current–voltage measurements and optical absorption spectroscopy. In FTO/MoO₃/P3HT/Al devices, increasing the MoO₃ thickness from 2 to 20 nm reduced the turn-on voltage and increased the forward current. Compared with the P3HT-only region, the P3HT/MoO₃ region exhibited an increase in absorbance at 650–720 nm. The absorbance in the 650–720 nm also tended to increase with MoO₃ thickness. These results suggest that chemical interactions between P3HT and MoO₃ generate energetically distributed gap states that could facilitate carrier injection.