Modulating Electronic Properties and Charge Transfer Dynamics of Graphene - P3HT Hybrid Heterostructures

This study presents a comprehensive investigation of the structural, electronic, and interfacial properties of regioregular poly(3-hexylthiophene) (P3HT) in contact with graphene substrates, focusing on monolayer, bilayer, and trilayer configurations. Ab-initio quantum chemical calculations are employed to examine the electronic properties and charge transfer dynamics between P3HT and graphene for both free-standing P3HT layers and P3HT interfaced with graphene, providing key insights into how graphene modulates the structural and electronic behavior of P3HT. The band structure analysis reveals a marked decrease in the band gap with increasing P3HT layer thickness. The band gap of free-standing P3HT decreases from approximately 1 eV in the monolayer to 0.71 eV in the bilayer and 0.54 eV in the trilayer. However, when P3HT is coupled with graphene, the band gap reduction is less pronounced, with values decreasing from 1.15 eV in the monolayer to 0.84 eV in the trilayer. This suggests that graphene interaction modulates the electronic structure of P3HT, resulting in higher band gaps compared to free-standing layers of the same thickness. Furthermore, the band structure of the P3HT molecule on graphene shows a band gap of 1.95 eV, reduced from the 2.57 eV intrinsic value, indicating significant interaction between P3HT and graphene. These findings provide crucial insights into optimizing charge transfer in P3HT-graphene heterostructures for applications in transistors and capacitors.