基于GaN纳米线的光化学电池型自供能紫外探测器的制备与性能研究

The ultraviolet (UV) photodetectors have been proposed for a variety of industrial and scientific applications, including communications, chemical/biological sensing, environmental monitoring, remote controlling, binary switches in imaging techniques, as well as in future memory storage and optoelectronic circuits. One-dimensional (1D) nanostructure UV photo detectors based on photoconductivity have been demonstrated to be excellent candidates for applications. However, this kind of photodetectors exhibits a surroundings-dependent behavior and a long recovery time due to the presence of a carrier depletion layer at surface of the nanomaterials caused by surface trap states. Moreover, such photodetectors needs to be driven by electric power, which is usually provided by batteries or other energy storage/supply systems. As the development of sensor network that contain huge amounts of small sensors, energy supply for such sensor systems is one of the main challenges to human beings in the 21st century. .Recently, self-powered nanodevices and nanosystems which can function well without an external power source have attracted increasing attentions. Self-powered UV photodetectors have been reported in terms of their dispense with external power sources, fast time response, low dark current and high sensitivity in a variety of detector structures such as Schottky and p-n junction type and photoelectrochemical cell (PECC) type. Of the various self-powered UV photodetectors, the PECC-type is more promising due to its key advantages: low-cost, simple manufacturing process, and composed of abundant and nontoxic raw materials. However, it is still a challenge to further increase the performance of the PECC-based photodetectors due to the nature drawbacks of metal oxide (MO) nanocrystalline films, such as numerous grain boundaries existing in the nanoparticles film and the slower electron mobility of MO as compared with other materials such as GaN..To overcome these limitations and achieve overall practical advantages in PECC-based photodetectors, here we report a GaN /MO core-shell nanostructure network that serves as a working electrode for efficient PECC-type photodetectors..

紫外光探测在光通信、远程控制、环境监控、化学/生物传感器及未来存储器和光电集成有着重要的用途。然而传统的基于光电导效应的紫外光探测器响应时间长且需外加电源，限制了其实际应用。基于此，自供能型纳米传感器件及系统将成为今后发展的趋势。基于光电化学电池型（PECC）的自供能紫外光探测器由于成本低廉、制造过程简单及环境友好等优势，越来越受到广泛的关注。然而以TiO2为代表的纳米晶膜的PECC光电探测器由于界面复合和电子传输能力的不足导致了载流子收集效率低，严重地制约了器件性能的提高。针对该瓶颈问题，在已有的研究基础上，本项目拟：1）选用具有更高电子迁移率的GaN纳米线形成电子的高效收集网络；2）在GaN纳米线上包覆如TiO2等材料以达到快速注入电子和减小界面复合的目的。该研究方案着眼于解决当前自供能紫外光探测器的瓶颈问题，为实现性能优越、易于工业化生产的新型自供能紫外探测器提供科学依据。

紫外光探测在光通信、远程控制、环境监控、化学/生物传感器及未来存储器和光电集成有着重要的用途。本项目利用静电方法和CVD方法制备了GaN纳米结构，研究了前驱物浓度、合成温度等对GaN纳米结构的形貌及结构的影响。将获得GaN纳米材料应用于光电化学型紫外探测器的光阳极，研究发现随着合成温度的升高，GaN纳米颗粒结晶性更好，紫外探测器性能也更加优异。进一步用TiO2对GaN纳米多孔薄膜进行改性，GaN-TiO2异质结的形成，使得电子空穴对可以快速分离，提高了载流子寿命，从而使得器件的响应度达到了0.315 A/W，响应时间低于0.03 s，短路电流密度达到了152.2 μAcm-2。纳米多孔薄膜的确可以提供大的比表面积，但是大量晶界的存在不利于载流子的传输，而一维纳米结构可以为载流子提供直接快速的传输通道。本项目进一步利用静电纺丝的方法制备了GaN 纳米线，纳米线长达毫米量级而且长径比均一，直径为50~60 nm。将其用于紫外探测器的光阳极，发现基于GaN 纳米线光电化学型紫外探测器相比于基于GaN纳米多孔薄膜光电化学紫外探测器的响应电流密度对光强响应灵敏度斜率达到0.27，比GaN纳米多孔薄膜高出69%。然而静电纺丝合成的GaN纳米线仍然由GaN纳米颗粒构成的，同样存在较多的晶界，项目进一步利用水热法并结合氨化法制备了GaN 纳米棒。纳米棒相对于纳米线同样可以为电子提供直接的传输通道，但是结构更加稳定，纳米棒同样可以为电子提供直接的传输通道，但是晶界更少。项目将其用于紫外探测器的光阳极，研究发现基于GaN 纳米线光电化学紫外探测器的短路电流密度达到24.2 μAcm-2，是同等条件下GaN 纳米线光阳极的138%，响应电流密度对光强灵敏度达到0.52。