Photodetector Based On PbSe Colloidal Quantum Dots

At present, the research of quantum dot(QD) photodetector is mainly focused on PbS colloidal QDs due to their decent stability. However, theoretically PbSe QDs have better device performance than PbS QDs, because PbSe QDs pocess better transport in the form of thin film(QD solid). Therefore, we tried to use air-stable PbSe quantum dots to fabricate photodetectors for the first time.Recently, cation exchange is being shown as an alternative to conventional hot-injection and heating-upsyntheses for colloidal quantum dots. Generally, the cation exchange reaction preserves the size and morphology of the reactant nanocrystals, producing crystal phase, shape, and novel heterostructures, that are not accessible by conventional synthesis. The cation exchange involves formation of a new phase and ligation of the exchanged cation in solution. Therefore, the thermodynamic driving force for the cation exchange is a balance between the solvation energy of the cation and the lattice binding energy before and after exchange. In the present work, the in situ cation exchange is applied to synthesize monodies persive PbSe quantum dots which are co-passivated with Cl and Cd. Due to the hybrid passivation, the PbSe QDs exhibits excellent stability in air when dispersed in hexane.First of all, PbSe quantum dots were prepared by cation exchange with in situ chloride and cadmium passivation using CdSe QDs as the starting materials. Then we tried to fabricate photodector based on the air-stable QDs. Secondly, we studied the effect of thiols with different length of carbon on the optoelectronic properties of QD thin film. Finally, the photodetectors were characterized using UV-visible-IR absorption spectra, TEM and semiconductor parameter analyzer.