Compositionally controlled, light-emitting, group IV semiconductor nanomaterials have potential to enable on-chip data communications and infrared (IR) imaging devices compatible with the complementary metal−oxide−semiconductor (CMOS) technology. The recent demonstration of a direct band gap laser in Ge-Sn alloys opens avenues to the expansion of Si-photonics. Ge-Sn alloys showed improved effective carrier mobility as well as direct band gap behavior at Sn composition above 6–11%. In this work, Ge1−xSnx alloy nanoparticles with varying Sn compositions from x = 0.124 to 0.178 were prepared via colloidal synthesis using sodium borohydride (NaBH4), a mild and non-hazardous reducing reagent. Successful removal of the synthesized long-alkyl-chain ligands present on nanoparticles’ surfaces, along with the passivation of the Ge-Sn nanoparticle surface, was achieved using aqueous (NH4)2S. The highly reactive surface of the nanoparticles prior to ligand exchange often leads to the formation of germanium oxide (GeO2). This work demonstrates that the (NH4)2S further acts as an etching reagent to remove the oxide layer from the particles’ surfaces. The compositional control and long-term stability will enable the future use of these easily prepared Ge1−xSnx nanoalloys in optoelectronic devices.

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We have developed a manufacturing friendly process for CIS solar cells that includes all-solid-state processing and an inert gas, atmospheric pressure selenization/anneal. Present efficiencies are in the 9 -10% range with V, 's at 400 + mV. Correlations between processing and performance have been established. Recent V, 's have been advanced to 430 mV using an etching process. These results combined with insights provided by a recombination model indicate that V, 's in excess of 500 mV are within reach.

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