Roles of amorphous and crystalline regions in determining the optical and electronic properties of donor:acceptor systems comprising poly(3-hexylthiophene) embedded with nitrogen/sulfur-doped graphene quantum dots

Herein, we present a joint experimental and theoretical study using a multiscale computational simulation approach focusing on the roles of amorphous and crystalline regions in determining the optical and electronic properties of hybrid systems comprising poly(3-hexylthiophene) (P3HT) embedded with nitrogen- (N-GQDs) and nitrogen/sulfur-doped graphene quantum dots (NS-GQDs). The degree of crystallinity calculated with our experimental X-ray diffraction patterns is supported by our molecular dynamics calculations for the amorphous and crystalline models. Resonance and off-resonance Raman, UV-Vis and impedance spectroscopy allowed us to demonstrate the enhancement in electronic charge transfer for both the amorphous and crystalline regions, particularly in the case of the P3HT:NS-GQDs. Our DFT calculations corroborate the presence of donor:acceptor interactions for the P3HT:NS-GQDs, while the opposite was observed for the P3HT:N-GQDs, in strong correlation with experimental data. Enhancing the knowledge of these fundamental aspects can be very useful for understanding the role of GQDs in polymeric solar cells and contributes to guiding their more rational design.