{"id":5392,"date":"2012-07-03T20:33:49","date_gmt":"2012-07-03T20:33:49","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/?p=5392"},"modified":"2012-07-18T22:30:53","modified_gmt":"2012-07-18T22:30:53","slug":"quantum-dot-light-emitting-diodes-with-an-electrophoretically-deposited-quantum-dot-layer","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/quantum-dot-light-emitting-diodes-with-an-electrophoretically-deposited-quantum-dot-layer\/","title":{"rendered":"Quantum Dot Light Emitting Diodes with an Electrophoretically Deposited Quantum Dot Layer"},"content":{"rendered":"

Quantum dot light emitting diodes (QD-LEDs) are promising devices for the next generation of solid-state lighting and other optoelectronic applications. QD-LEDs have several potential advantages over current technologies due to the unique properties of quantum dots, such as a very narrow and easily tunable emission bandwidth, broad excitation spectrum, high brightness, and improved shelf life over organic dyes (used in organic LEDs) [1<\/a>] <\/sup> [2<\/a>] <\/sup> [3<\/a>] <\/sup>. Quantum dot films for QD-LEDs are conventionally formed via spin-casting, which is a reliable but highly non-scalable process. To date, a few alternatives to spin-casting have been researched, but due to its simplicity, spin-casting remains the most common technique for forming dot films for QD-LEDs.<\/p>\n

We investigated electrophoretic deposition (EPD) as an alternative method to spin-casting for the deposition of quantum dot films. Electrophoretic deposition is an experimentally simple, well-established technique that has been used to deposit a variety of materials [4<\/a>] <\/sup>. In addition to offering the potential for parallel processing and for less material waste during processing, EPD could potentially create more ordered films than spin-casting. We fabricated QD-LEDs (Figure 1) with an electrophoretically deposited CdSe\/ZnS core-shell QD film. EPD is performed by submerging 2 ZnO-on-ITO electrodes into a solution of QDs in a sonication bath and applying a DC field of ~25 V\/cm for 5 minutes between the electrodes. Completed QD-LEDs fabricated with an electrophoretically deposited dot layer exhibited sub-bandgap turn-on voltages of ~1.8 V and peak external quantum efficiencies (EQE) of ~1.6%, a number comparable to that of QD-LEDs fabricated with a conventional spun-on dot layer (Figure 2). These findings demonstrate that EPD is a viable alternative to spin-casting for the large-area, high-throughput fabrication of QD-LEDs with respectable performance.<\/p>\n\n\t\t