Handa Taketo, Tahara Hirokazu, Aharen Tomoko, Kanemitsu Yoshihiko
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Sci Adv. 2019 Jul 19;5(7):eaax0786. doi: 10.1126/sciadv.aax0786. eCollection 2019 Jul.
Lead halide perovskites are promising semiconductors for high-performance photonic devices. Because the refractive index determines the optimal design and performance limit of the semiconductor devices, the refractive index and its change upon external modulations are the most critical properties for advanced photonic applications. Here, we report that the refractive index of halide perovskite CHNHPbCl shows a distinct decrease with increasing temperature, i.e., a large negative thermo-optic coefficient, which is opposite to those of conventional inorganic semiconductors. By using this negative coefficient, we demonstrate the compensation of thermally induced optical phase shifts occurring in conventional semiconductors. Furthermore, we observe a large and slow refractive index change in CHNHPbCl during photoirradiation and clarify its origin to be a very low thermal conductivity supported by theoretical analysis. The giant thermo-optic response of CHNHPbCl facilitates efficient phase modulation of visible light.
卤化铅钙钛矿是用于高性能光子器件的很有前景的半导体。由于折射率决定了半导体器件的优化设计和性能极限，因此折射率及其在外部调制下的变化是先进光子应用中最关键的特性。在此，我们报道卤化钙钛矿CHNHPbCl的折射率随温度升高而明显降低，即具有很大的负热光系数，这与传统无机半导体的情况相反。通过利用这种负系数，我们展示了对传统半导体中热致光学相移的补偿。此外，我们观察到CHNHPbCl在光照射期间折射率有大且缓慢的变化，并通过理论分析阐明其起源是极低的热导率。CHNHPbCl的巨大热光响应有助于实现可见光的高效相位调制。
