Size-tunable band gap materials offer an advantageous method for developing high efficiency solution processed nanocrystal optoelectronic devices. The effect grain size on charge transfer across thin films was investigated by varying the CdSe nanocrystal size via control of the nanocrystal synthesis. Additionally, growing CdS/CdSe core/shell materials with various shell thicknesses allowed for the investigation of the effects of quantum confinement, due to the confinement of photogenerated holes and electrons to the CdSe shell layer. Comparing the photoconductivity of confined (2.6 nm diameter) and non-confined (13 nm diameter) CdSe has shown a 15-fold greater conductivity for large CdSe. Grain size has shown to be more significant factor than quantum confinement for thin film conductivity.  However, the role of quantum confinement was investigated independent of grain size via CdS/CdSe nanoshells. The CdS core dimensions are allowed to exceed the exciton Bohr radius, which leads to nanostructures approaching 30 nm in total diameter while exhibiting CdSe shell quantum confinement. By adjusting the dimensions of CdS/CdSe materials even greater thin film photoconductivity than CdSe (of the same size) is achieved by taking advantage of both grain size and quantum confinement effects on photo-induced charge transfer.<br/>

Investigation of the effects of quantum confinement and grain size on the photoconductivity of CdSe nanocrystal thin films

2019 Fall National Meeting

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