Optoelectronic Properties and Charge Transfer Dynamics of Graphene - P3HT Hybrid Materials

We provides a computational analysis of the structural, electronic, and optical characteristics of regioregular poly(3-hexylthiophene) (P3HT) in contact with graphene substrates, considering monolayer, bilayer, and trilayer configurations. Using ab initio quantum chemical calculations that incorporate van der Waals interactions, the study explores the electronic structure and charge transfer behavior of both free-standing P3HT layers and P3HT-graphene composites. The results reveal how graphene influences the structural and electronic responses of P3HT. Band structure analyses show that the band gap of free-standing P3HT decreases with increasing layer thickness—from about 1 eV in the monolayer to 0.71eV in the bilayer and 0.55eV in the trilayer. In contrast, when P3HT interacts with graphene, the band gap reduction is less significant, ranging from 1.15eV in the monolayer to 0.84eV in the trilayer. This indicates that graphene coupling modifies the electronic structure of P3HT, maintaining relatively larger band gaps than those of the corresponding free-standing layers. Moreover, the P3HT molecule adsorbed on graphene exhibits a reduced band gap of 1.95 eV compared to its intrinsic value of 2.57 eV, reflecting a strong interfacial interaction. Overall, these findings highlight how graphene–P3HT interactions can be leveraged to tune charge transfer processes in heterostructures relevant to photovoltaic and solar cell technologies.