The researchers prepare their devices by creatively conjugating poly (3-hexylthiophene)(P3HT) onto carbon nanotubes by π-π interactions and avoiding chemical modifications. Through photoluminescence characterization and carrier mobility measurements, the role of semiconducting carbon nanotubes in the photovoltaic conversion is revealed.

A filtration process is used to tailor the purity of semiconducting carbon nanotubes and adjust the dispersion morphology of the material in the conjugated composites. Further thermal annealing helps to improve the structure of nanotube/P3HT composites and forms a type-II heterojunction. As a result, both short-circuit current and open-circuit voltage are significantly enhanced, and the power conversion efficiency is increased by 80%.

The techniques outlined in the study can be extended to other organic photovoltaic systems, and may pave a way to affordable and efficient solar cells.

More details can be found in the journal Nanotechnology.