We have been actively seeking a nanocrystal materials system that enables photovoltaics (PVs) to be printed at room temperature on a variety of substrates with sufficient performance and stability to enable low-cost, lightweight portable power applications. CuInSe2 nanocrystals have exhibited some success in this direction, but the power conversion efficiency of the devices has been limited to 3-4%. Simulations of CuInSe2 nanocrystal PVs indicate that higher performance is not likely to be achieved though ligand exchange procedures that influence electron affinity as reported for PbS nanocrystal PVs, but will require increased carrier mobility and lifetimes. Both characteristics are influenced by capping ligand chemistry and defects. Raman spectroscopy reveals that the CuInSe2 nanocrystals contain a significant concentration of InCu+2VCu pair defects, which depends on the synthesis conditions. These pair defects tend to order under light excitation and can be eliminated by high temperature annealing. 1H-NMR spectroscopy indicates that oleylamine and diphenylphosphine capping ligands used in a typical CuInSe2 nanocrystal synthesis bind strongly to the nanocrystal surface and do not allow ligand exchange to readily occur. Addition of I2, however, induces ligand desorption and facilitates ligand exchange. These studies provide insight for improving the performance of CuInSe2 nanocrystal photovoltaics.

Copper indium selenide nanocrystal defects and surface chemistry

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.