Improvement of device performance of QD-polymer hybrid LEDs by synergy effect of exciton energy and charge transport

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04153
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Shinshu University
• Principal Investigator: Itoh Eiji 信州大学, 学術研究院工学系, 教授 (50303441)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 半導体量子ドット / 有機EL / 逆構造 / 酸化物ナノ材料 / 電子注入層 / 正孔注入層 / 塗布プロセス

Outline of Final Research Achievements

Semiconductor quantum dots and polymer functional materials have complementary properties in terms of electron transport and hole transport, and exciton energy. In this study, we developed a solution-processable hybrid LED in which an extremely thin light-emitting layer consisting of a QD/polymer blend is deposited on the ZnO nanoparticle film, and a hole-transporting polymer film is laminated on top of emitting layer. The big problem of electron injection from ZnO to the blue-emitting polymer was easily solved by replacing it with QD:polymer blend. The hole injection was improved by double-layered hole transporting polymer layers, resulting in achieving a reduction of operating voltage and higher efficiency. By inserting an extremely thin oxide film at the interface between the ZnO and EML, we demonstrated further thinning, low voltage, and high efficiency.

Free Research Field

有機エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

高分子系の発光ダイオードは塗布形成により大面積化や製造コストの低減が期待できるが燐光材料やTADFに比べ効率が低く、厚さ数10nmの塗布膜にはミクロのピンホールが生じやすく漏れ電流や導通が多く歩留まりが低かった。また、発色性に優れる量子ドットや高効率発光ポリマーは1g数10万円を超えるため、極限まで薄く無駄なく製膜することが要求される。本研究はメニスカスと転写法を改良して材料利用率をスピンコートの10倍以上(>50%)とした点に加え、キャリア注入層やブロッキング層を改良し従来よりも薄くして導通も減らして効率と動作電圧を改善しており、経済的で効率と発色の両者を改良し実用化の課題解決策を実証した。