Nickel oxide (NiO_x) has been extensively adopted as a promising hole transport material for perovskite light-emitting diodes (PeLEDs). However, its shallow valence band induces a large hole injection barrier for pure-blue PeLEDs with moderate device performances. Herein, an ingenious interface layer of ammonium molybdate (AMM) is proposed to successfully tailor the NiO_x energy band for fast hole injection. After careful comparisons with pristine NiO_x and conventional MoO₃ modification layer, we demonstrate the superior capacity of AMM to precisely tune the valence band of NiO_x for efficient hole injection and thus, a balanced charge injection in the devices. As a result, we reveal the favorable energy band of NiO_x-AMM for one of the best-performing pure-blue PeLEDs with an impressive efficiency of 9.15% at 473 nm and a high brightness of 5550 cd m^–2. More importantly, we demonstrate a remarkably low turn-on voltage of 2.4 V, being the smallest turn-on voltage for pure-blue PeLEDs through a sufficient hole injection. Consequently, this work contributes to a feasible and efficient approach to tailor the NiO_x energy band for highly performing pure-blue PeLEDs.

中文翻译：

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为高性能蓝色钙钛矿发光二极管提供足够的空穴注入


氧化镍 （NiO_x） 已被广泛用作钙钛矿发光二极管 （PeLED） 的空穴传输材料。然而，其浅价带为具有中等器件性能的纯蓝色 PeLED 诱导了大的空穴注入势垒。在此，提出了一种巧妙的钼酸铵 （AMM） 界面层，以成功定制 NiO_x 能带以实现快速空穴注入。在与原始 NiO_x 和传统的 MoO₃ 改性层仔细比较后，我们证明了 AMM 的卓越能力，可以精确调节 NiO_x 的价带以实现高效的空穴注入，从而在器件中实现平衡电荷注入。结果，我们揭示了 NiO_x-AMM 对性能最好的纯蓝色 PeLED 之一有利的能带，在 473 nm 处具有令人印象深刻的 9.15% 效率和 5550 cd m^–2 的高亮度。更重要的是，我们展示了 2.4 V 的极低导通电压，通过足够的空穴注入，它是纯蓝色 PeLED 的最小导通电压。因此，这项工作有助于为高性能纯蓝光 PeLED 定制 NiO_x 能带的可行且有效的方法。