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The charge carrier balance and performance of CdSe/ZnS quantum-dot light-emitting diodes (QD-LEDs) with a vacuum-deposited electrontransport layer (ETL) and carrier-restricting layer (CRL) were successfully improved. Optimizing the fabrication process of the reactively sputtered zinc-tin-oxide (ZTO) ETL and adopting a thermally evaporated tungsten-oxide (WO x ) CRL improved the electron-hole balance, thus leading to QD-LEDs with improved performance. Impedance spectroscopy analysis was successfully exploited in investigating charge carrier injection into each layer of the QD-LED and electron-hole recombination behaviors. The QD-LED with optimized ZTO ETL and without WO x CRL exhibited 2600 cd m −2 luminance and 3.2 cd A −1 current efficiency, and the QD-LED with both optimized ZTO ETL and a WO x CRL exhibited 3900 cd m −2 luminance and 5.1 cd A −1 current efficiency. These results imply a practical method for improving the electron-hole balance and performance of QD-LEDs, and provide a reliable technique for analyzing the carrier behavior of QD-LEDs.

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Quantum-dot light-emitting diodes (QD-LEDs) with a sputtered zinc tin oxide (ZTO) electron-transporting layer (ETL) were studied. A ZTO after-deposition treatment process consisting of oxygen plasma treatment and thermal annealing was studied to improve the performance of the sputtered metal oxide ETL. The optical and electrical properties of the ZTO ETL could be controlled by adjusting the thermal annealing temperature. The best performing QD-LED was obtained by applying the oxygen plasma treatment and 250 °C thermal annealing in N2 atmosphere in sequence. The relation between the ZTO ETL properties and the device performance was explained by considering the roles of the band gap defect states. In this work, we provide a way to control the ZTO ETL properties and to improve the QD-LED device performance by applying an after-deposition treatment to the ZTO ETL.

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