We report solar cells based on highly confined nanocrystals of the ternary compound PbSxSe1-x. Crystalline, monodisperse alloyed nanocrystals are obtained using a one-pot, hot injection reaction. Rutherford back scattering and energy filtered transmission electron microscopy suggest that the S and Se anions are uniformly distributed in the alloy nanoparticles. Photovoltaic devices made using ternary nanoparticles are more efficient than either pure PbS or pure PbSe based nanocrystal devices.

Natural and artificial photosynthesis both require a precisely organized structure with multiple components for an efficient charge transfer pathway. The development of nanotechnology enables us to scale these sophisticated structures from bulk to nanometer-size by providing tunable physical and electronic properties. In order to achieve sophisticated nanostructures, lithographic techniques are commonly used to arrange those components in arbitrary patterns. However, lithographed materials are not easy to be scaled up, and it is hard to study the electronic picture due to the lack of well-defined facets and crystalline structure. There has been a surge of interest in exploring the effect of metal colloidal nanoparticle in photochemistry. The localized surface plasmon resonance property of the metal nanoparticle generates energetic charge carriers above the fermi energy of the metal. Interestingly, the energy of the charge carrier is greatly dependent on the morphology of the structure which can harvest photons over the entire solar spectrum. However, since the lifetime of carriers is extremely short compared to the semiconductor nanoparticles, other components are required to capture the energetic electrons from the metal nanoparticle. Thus, sophistically incorporating multiple components on the metal nanoparticle offers an effective way to use hot carriers of the metal nanoparticle. These complex structures based on the metal nanoparticle can further shed light on diverse applications such as plasmonics and photocatalysis. This dissertation lays out a novel synthetic approach to fabricate a function-oriented colloidal polyelement nanostructure using a solution-phase redox chemistry. Furthermore, we demonstrate that such a sophisticated nanostructure can effectively improve the photocatalytic efficiency of hydrogen and oxygen evolution reaction without the use of any scavenger. I truly believe that this thesis work can inspire the material research community for the development of a new library to manipulate the chemical and physical properties of matter.