Single nanoparticle of organic p-type and n-type hybrid materials: Nanoscale phase separation and photovoltaic effect

We fabricated hybrid nanoparticles (NPs) of p-type poly(3-hexylthiophene) (P3HT) and n-type fullerene derivative {[6,6]-phenyl C ₆₁-butyric acid methyl ester (PCBM)} materials through a mini-emulsion method. The nanoscale photoluminescence (PL) characteristics of the non-annealed and annealed hybrid single NPs with different concentrations of P3HT and PCBM were investigated using a laser confocal microscope (LCM) with high spatial resolution. The luminescence characteristics corresponding to the P3HT and PCBM materials were observed simultaneously in the LCM PL spectra for P3HT/PCBM hybrid NP after the annealing process. We propose that the annealing process for the hybrid NPs assisted the ordering of P3HT main chains and the formation of PCBM domains through the gathering of the molecules, indicating nanoscale phase separation. This was supported by UV-Vis absorption and Raman spectroscopy results. Conducting atomic force microscope experiments on an annealed hybrid single NP allowed for the measurement of the characteristic photoresponsive current-voltage curves, and monochromatic photovoltaic characteristics and the avalanche photodiode effect were observed in the low- and high-bias regions, respectively.