The upconversion (UC) emission behavior occurs usually in rare-earth doped compounds but rarely in pure semiconductors. Herein, the UC emission behavior of WO3 was investigated. The oxygen-vacancy-rich WO3 nanosheets were rapidly synthesized by high-power laser irradiation. The red UC emission peaked at ∼1.75 eV is observed in the synthesized WO3 nanosheets under continuous 980 nm or 1940 nm laser excitation. The UC emission stems from the abundant oxygen-deficient levels and belongs to a multiphoton absorption behavior. Meanwhile, the laser-power-dependent UC behavior could be attributed to the transformation of different oxygen defect states. On this basis, a variable output color phosphor based on Er-Yb co-doped WO3 [WO3:(Er, Yb)] was developed. The WO3:(Er, Yb) phosphor can change the UC color from green to red with increasing the 980-nm laser power. Moreover, the upconversion behavior of WO3 can be utilized to assist WS2 photocatalysis. This work develops a pure semiconductor with an interesting UC emission and clarifies the UC mechanism.

中文翻译：

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近红外激光激发下 WO3 纳米片的红色上转换发射


上转换 （UC） 发射行为通常发生在稀土掺杂化合物中，但很少发生在纯半导体中。本文研究了 WO ₃ 的 UC 发射行为。通过高功率激光照射快速合成了富含氧空位的 WO ₃ 纳米片。在连续 980nm 或 1940 nm 激光激发下，在合成的 WO ₃ 纳米片中观察到峰值为 ~1.75eV 的红色 UC 发射。UC 发射源于丰富的缺氧水平，属于多光子吸收行为。同时，激光功率依赖性的 UC 行为可归因于不同氧缺陷状态的转变。在此基础上，开发了一种基于 Er-Yb 共掺杂 WO ₃ [WO ₃ :(Er， Yb）] 的可变输出彩色荧光粉。WO ₃ :(Er， Yb） 荧光粉可以随着 980 nm 激光功率的增加将 UC 颜色从绿色变为红色。此外，WO 的上转换行为 ₃ 可用于辅助 WS ₂ 光催化。这项工作开发了一种具有有趣 UC 发射的纯半导体，并阐明了 UC 机制。