Amorphous dielectric metal-organic electron injection layer for efficient inverted organic light-emitting diodes
Amorphous dielectric metal-organic electron injection layer for efficient inverted organic light-emitting diodes
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DOI：
10.1016/j.orgel.2023.106878
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发表时间：
2023
影响因子：
3.2
通讯作者：
Lina Sun;Tsukasa Yoshida;Y. Harada;M. White;Yoshiyuki Suzuri
中科院分区：
文献类型：
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作者：
Lina Sun;Tsukasa Yoshida;Y. Harada;M. White;Yoshiyuki Suzuri
研究发现，溶液处理的金属有机薄膜可在倒置有机发光二极管 (iOLED) 中充当高效且稳定的电子注入层 (EIL)。甲氧基乙醇锌 (II) (ZME) 在 N2 下温和退火，在高度致密的无定形 ZME (ag-ZME) 凝胶中产生 ZnO (nc-ZnO) 纳米晶体。虽然结晶良好的 ZnO 会导致强烈的电子泄漏，从而降低器件效率，但在低至 30°C 的温度下加工的 ag-ZME 确实可以有效地工作。直流电容分析揭示了ag-ZME的高介电行为，可实现选择性电子注入发射层，同时防止空穴的非发射直接还原，这与具有带内缺陷态的晶体ZnO不同，会导致电子泄漏。我们还使用甲氧基乙醇钙 (II) (CME) 作为 EIL，并在 iOLED 中展示了几乎相同的性能。 ag-CME和ag-ZME中Ca(II)和Zn(II)的4s轨道用于调节电子注入，而晶体ZnO的过高电导率只会降低效率。通过在 100°C 退火，具有平衡 nc-ZnO/ag-ZME 的 iOLED 实现了 25.5 cd A−1 的高电流效率和超过 2000 h @100 cd m−2 的工作半衰期稳定性，使其在 iOLED 中的实际应用具有吸引力。
Solution processed metal organic thin film was found to act as an efficient and stable electron injection layer (EIL) in inverted organic light emitting diodes (iOLEDs). Mild annealing of zinc(II) methoxyethoxide (ZME) under N2resulted in nanocrystals of ZnO (nc-ZnO) within highly compact amorphous gel of ZME (ag-ZME). While well-crystallized ZnO caused a strong electron leakage to reduce device efficiency, the ag-ZME processed at a temperature as low as 30 °C did work efficiently. DC capacitance analysis revealed a highly dielectric behavior of ag-ZME that achieves selective electron injection to the emission layer, while preventing non-emissive direct reduction of hole, unlike crystalline ZnO with intra-band defect states to cause electron leakage. We also employed calcium(II) methoxyethoxide (CME) as an EIL and demonstrated almost the same performance in iOLEDs. The 4s orbitals of Ca(II) and Zn(II) in ag-CME and ag-ZME are used to regulate the electron injection, whereas the redundantly high conductivity of crystalline ZnO can only reduce the efficiency. The iOLED with a balanced nc-ZnO/ag-ZME by annealing at 100 °C achieved a high current efficiency of 25.5 cd A−1and an operating half-life stability exceeding 2000 h @100 cd m−2, appealing for its practical use in iOLEDs.