时间分辨光电导谱定量化研究金属氧化物的光生载流子动力学

Recently a study named “A Photoconductor Intrinsically Has No Gain” drew attention as it proved a well-accepted theory that “photogain theory in semiconductor photoconductive device” was intrinsically wrong. Due to the lack of quantification methods for dissecting the dynamics of photocarriers in semiconductors, the controversies continue. Given this background, this project aims to develop a method to quantitatively study the photocarrier dynamics in semiconductors by using time-resolved photoconductance spectrum (tr-PCS) measurements. First, metal oxide semiconductors (MOS) are selected as the research objects; the reasonable hypotheses will be proposed on the basis of the controversies in the recent studies on photocarrier dynamics, and then the photophysical models will be established accordingly; through fitting the measured tr-PCSs with the photophysical models, a large number of photophysical variables could be obtained quantitatively to deeply analyze the photocarrier dynamics in MOS and then prove the controversies in the “photogain theory in semiconductor photoconductive device” as well as other relative photophysical theories. Second, through reducing a series of strongly correlated variables in the photophysical models, a universal method will be proposed to quantitatively analyze the tr-PCS, which could be widely used for studying the photocarrier dynamics in MOS. Finally, the photocarrier dynamics of MOS hetero-nanocomposites will be studied by using the tr-PCS developed quantitative analysis method, and hence, important photophysical parameters, such as quantum yields, charge carrier transfer rates at heterointerface, will be extracted quantitatively. Overall, this project could pave a new method and lay the theoretical foundation for quantitatively studying the photocarrier dynamics in semiconductors.

“半导体光电导器件本质上无增益”。近日，存在50多年的“半导体光电导器件增益理论”被认为是错误的。由于缺乏定量化表征半导体光生载流子动力学的方法，类似的争议越来越多。为此，本项目拟利用时间分辨光电导谱发展一种定量化表征光生载流子动力学的方法。首先，以金属氧化物（MOS）为研究对象，针对研究争议，提出理论假说，建立相应的物理模型，用于拟合时间分辨光电导谱、定量求解物理参量，从而全面剖析MOS的光生载流子动力学，论证“半导体光电导器件增益理论”等相关理论争议。然后，约化物理模型中强关联性的物理量，进而建立一种普适的时间分辨光电导谱的定量化分析方法，用以广泛研究MOS的光生载流子动力学。最后，以时间分辨光电导谱为表征方法，研究MOS异质结纳米复合物的光生载流子动力学，定量获取量子产率、异质界面电荷转移速率等参数。本项目旨在为定量化研究半导体的光生载流子动力学提供新的方法和理论基础。

具有光敏感和光响应特征的金属氧化物半导体及其复合物在环境、能源、信息等领域已经展现出了非常重要的应用价值。尽管如此，由于缺乏定量化表征半导体光载流子动力学的方法，相关领域的理论争议越来越多。例如，近几年有学者认为存在数十年的半导体光电导器件增益理论是错误的，半导体光电导器件本质上无增益。为此，本项目利用时间分辨光电导谱的实验方法，结合光载流子动力学理论分析，发展了一种定量化表征光载流子动力学过程、提取特征物理参数的方法。本项目的主要结果包括：（1）以ZnO纳米颗粒膜为研究对象，测试了时间分辨光电导谱，并使用动力学方程进行拟合、分析，发现：在小注入条件下，光载流子来源于缺陷光离化，在入射光子数大于本征施主缺陷浓度时，光载流子来源于缺陷光离化和电子空穴对的光激发；（2）检验了时间分辨光电导谱可以广泛用于分析金属氧化物的内禀和外禀的光载流子动力学过程；（3）以时间分辨光电导谱为表征方法，通过建立载流子动力学方程，研究了多种异质结纳米复合物的光载流子动力学过程，定量获取了量子产率、光载流子寿命、异质界面电荷转移速率等参数。本项目旨在为量化研究半导体的光载流子动力学提供新的方法和理论基础，通过使用动力学方程解析时间分辨光电导谱，定量获取物理特征参数，以此来评价金属氧化物及其复合物在光催化、光探测器、光存储等领域的应用前景。