Origin of Low Open-Circuit Voltage in Surfactant-Stabilized Organic-Nanoparticle-Based Solar Cells

Organic-nanoparticle-based solar cells have drawn great attention due to their eco-friendly and environmentally friendly fabrication procedure. However, these surfactant-stabilized nanoparticles suffer open-circuit voltage loss due to charge trapping and poor extraction rate at the polymer cathode interface. Here, we have investigated the origin of voltage loss and charge trapping in surfactant-stabilized nanoparticle-based devices. Efficient organic photovoltaic (OPV) devices have been fabricated from an aqueous dispersion of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) nanoparticles stabilized by anionic surfactants. AC impedance spectroscopy has been used to understand the charge transport properties in the dark and in operando conditions. We have demonstrated the similarities in the charge transport properties, as well as photocarrier dynamics of the nanoparticle-based OPVs and the bulk heterojunction OPVs despite fundamental differences in their nanostructure morphology. This study emphasizes the possibility of fabricating highly efficient OPVs from organic nanoparticles by reducing surface defects and excess doping of the polymers.