[11p-W833-1~12] 9.2 Nanoparticles, Nanowires and Nanosheets

▼ [11p-W833-7] Enhanced Electron Transport in Core@Shell Colloidal Quantum Dot Assemblies

〇(D)Retno Miranti¹, Satria Zulkarnaen Bisri^2,1, Maria Ibanez³, Maksym V. Kovalenko³, Yoshihiro Iwasa^2,4 (1.Tokyo Inst. Tech, 2.RIKEN CEMS, 3.ETH Zurich, 4.Univ. of Tokyo)

Keywords:Quantum Dots, Electron Transport

Quantum dots (QDs) assemblies are a new type of hybrid solid thin films that have a key advantage of size-dependent energy band gap variation of the individual QD. The colloidal nature of this class of materials makes it a promising candidate for solution-processable electronics applications. The ability to control the carrier transport in the nanocrystals assemblies is fundamental for altering its electronic and optical properties. Here we demonstrate a strategy to control hole and electron transport in QDs assembly by introducing shelling on lead chalcogenide QDs core. The QDs assemblies are crosslinked by short organic molecules that replaced the native insulating ligand. Properties of these assemblies were measured using both conventional solid gate and electric-double-layer transistor. The electronic transport measurement of core@shell QD assemblies of narrow band-gap Pb-chalcogenide QD, which was shelled by the larger band-gap Pb-chalcogenide shell, demonstrate n-type transport. This n-type transport characteristic is distinctive to what typically observed in their corresponding core-only QDs assemblies. The electron conductivity and mobility in this core@shell QDs is significantly higher than the value found in its core QDs assemblies. This finding suggests that shelling nanocrystal core using monolayers of another Pb-chalcogenide result in the formation of heterojunction that assist the selective carrier transport. In this case, the hole transport is suppressed by hole-localization in the core-valence level. In addition to the reported core-shell QDs, our study reveals an interesting finding that the shell may contribute as electron doping in the core@shell assemblies. The n-type transport makes these core@shell QDs more suitable for applications where ambipolar characteristics should be strongly suppressed to enhance their performance, such as photodetectors, thermoelectric, as well as a selective electron transporting layer.