The search for eco-friendly methods to develop electronic materials without toxic organic solvents has led to water-borne core-shell semiconductor nanoparticles (NP) for photovoltaic applications. Water-borne methods do not yet have the ability, however, to control how the core-shell structure develops for optimum performance. This study sought to understand and control how the core-shell structure develops and tune methods for higher efficiency materials. The water-borne NP method uses a surfactant-water phase plus a semiconductor organic phase. In previous work a surfactant-water phase that improved electronic interaction was developed, and in this study the goal was to increase charge separation efficiency, a characteristic that directly affects photovoltaic performance. Several NPs were synthesized and their performance compared. Devices were analyzed using small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Analysis clearly indicates the dependence of charge separation efficiency on the core-shell structure. Photovoltaic devices with the NPs also were fabricated.
Significance and Impact
Efficiency measurements corroborated the optimum protocol for developing the water-borne NPs. Results showed the important role shell morphology plays in the electrical activity of the device. This work provides a means to synthesize effective water-based organic semiconductors; photovoltaic cells with >5% efficiency were achieved.
At the Center for Nanoscale Materials, five groups of NPs were synthesized with varying phases and materials; performance parameters were measured; time-resolved photoluminescence, DLS, TEM, and UV-visible absorption spectroscopy were employed. At the Advanced Photon Source, small-angle X-ray scattering (SAXS) was performed at sector 12 beamline ID-B.
Work was performed at the Center for Nanoscale Materials and the Advanced Photon Source.
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