Li Shunran, Dai Zhenghong, Li Linda, Padture Nitin P, Guo Peijun
Department of Chemical and Environmental Engineering, Yale University, 9 Hillhouse Avenue, New Haven, Connecticut 06520, USA.
School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
Rev Sci Instrum. 2022 May 1;93(5):053003. doi: 10.1063/5.0083763.
Understanding thermal transport at the microscale to the nanoscale is crucially important for a wide range of technologies ranging from device thermal management and protection systems to thermal-energy regulation and harvesting. In the past decades, non-contact optical methods, such as time-domain and frequency-domain thermoreflectance, have emerged as extremely powerful and versatile thermal metrological techniques for the measurement of material thermal conductivities. Here, we report the measurement of thermal conductivity of thin films of CHNHPbI (MAPbI), a prototypical metal-halide perovskite, by developing a time-resolved optical technique called vibrational-pump visible-probe (VPVP) spectroscopy. The VPVP technique relies on the direct thermal excitation of MAPbI by femtosecond mid-infrared optical pump pulses that are wavelength-tuned to a vibrational mode of the material, after which the time dependent optical transmittance across the visible range is probed in the ns to the μs time window using a broadband pulsed laser. Using the VPVP method, we determine the thermal conductivities of MAPbI thin films deposited on different substrates. The transducer-free VPVP method reported here is expected to permit spectrally resolving and spatiotemporally imaging of the dynamic lattice temperature variations in organic, polymeric, and hybrid organic-inorganic semiconductors.
理解从微观尺度到纳米尺度的热输运对于从器件热管理和保护系统到热能调节与收集等广泛的技术至关重要。在过去几十年中，非接触光学方法，如时域和频域热反射，已成为用于测量材料热导率的极其强大且通用的热计量技术。在此，我们通过开发一种称为振动泵浦可见探测（VPVP）光谱的时间分辨光学技术，报告了典型金属卤化物钙钛矿CHNHPbI（MAPbI）薄膜的热导率测量。VPVP技术依赖于飞秒中红外光泵浦脉冲对MAPbI的直接热激发，该脉冲的波长调谐到材料的一种振动模式，之后使用宽带脉冲激光在纳秒到微秒的时间窗口内探测可见光范围内随时间变化的光学透过率。使用VPVP方法，我们确定了沉积在不同衬底上的MAPbI薄膜的热导率。本文报道的无换能器VPVP方法有望实现对有机、聚合物和有机 - 无机混合半导体中动态晶格温度变化的光谱分辨和时空成像。
