Large-Area (over 50 cm 脳 50 cm) Freestanding Films of Colloidal InP/ZnS Quantum Dots

详细信息    查看全文

• 作者：Evren Mutlugun ; Pedro Ludwig Hernandez-Martinez ; Cuneyt Eroglu ; Yasemin Coskun ; Talha Erdem ; Vijay K. Sharma ; Emre Unal ; Subhendu K. Panda ; Stephen G. Hickey ; Nikolai Gaponik ; Alexander Eychm眉ller ; Hilmi Volkan Demir
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：August 8, 2012
• 年：2012
• 卷：12
• 期：8
• 页码：3986-3993
• 全文大小：476K
• 年卷期：v.12,no.8(August 8, 2012)
• ISSN：1530-6992

文摘

We propose and demonstrate the fabrication of flexible, freestanding films of InP/ZnS quantum dots (QDs) using fatty acid ligands across very large areas (greater than 50 cm 脳 50 cm), which have been developed for remote phosphor applications in solid-state lighting. Embedded in a poly(methyl methacrylate) matrix, although the formation of stand鈥揳lone films using other QDs commonly capped with trioctylphosphine oxide (TOPO) and oleic acid is not efficient, employing myristic acid as ligand in the synthesis of these QDs, which imparts a strongly hydrophobic character to the thin film, enables film formation and ease of removal even on surprisingly large areas, thereby avoiding the need for ligand exchange. When pumped by a blue LED, these Cd-free QD films allow for high color rendering, warm white light generation with a color rendering index of 89.30 and a correlated color temperature of 2298 K. In the composite film, the temperature-dependent emission kinetics and energy transfer dynamics among different-sized InP/ZnS QDs are investigated and a model is proposed. High levels of energy transfer efficiency (up to 80%) and strong donor lifetime modification (from 18 to 4 ns) are achieved. The suppression of the nonradiative channels is observed when the hybrid film is cooled to cryogenic temperatures. The lifetime changes of the donor and acceptor InP/ZnS QDs in the film as a result of the energy transfer are explained well by our theoretical model based on the exciton鈥揺xciton interactions among the dots and are in excellent agreement with the experimental results. The understanding of these excitonic interactions is essential to facilitate improvements in the fabrication of photometrically high quality nanophosphors. The ability to make such large-area, flexible, freestanding Cd-free QD films pave the way for environmentally friendly phosphor applications including flexible, surface-emitting light engines.

Keywords:

Semiconductor quantum dots; large-area freestanding films; excitons; nonradiative energy transfer; white light generation; remote phosphors