Applied Science and Technology Graduate Program, University of California, Berkeley, California 94720, USA.
Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA.
Nat Commun. 2016 Jun 21;7:11924. doi: 10.1038/ncomms11924.
The sensitivity of semiconductor photodetectors is limited by photocarrier recombination during the carrier transport process. We developed a new photoactive material that reduces recombination by physically separating hole and electron charge carriers. This material has a specific detectivity (the ability to detect small signals) of 5 × 10(17) Jones, the highest reported in visible and infrared detectors at room temperature, and 4-5 orders of magnitude higher than that of commercial single-crystal silicon detectors. The material was fabricated by sintering chloride-capped CdTe nanocrystals into polycrystalline films, where Cl selectively segregates into grain boundaries acting as n-type dopants. Photogenerated electrons concentrate in and percolate along the grain boundaries-a network of energy valleys, while holes are confined in the grain interiors. This electrostatic field-assisted carrier separation and percolation mechanism enables an unprecedented photoconductive gain of 10(10) e(-) per photon, and allows for effective control of the device response speed by active carrier quenching.
半导体光电探测器的灵敏度受到载流子输运过程中光生载流子复合的限制。我们开发了一种新的光活性材料，通过物理分离空穴和电子电荷载流子来减少复合。这种材料的探测率（检测小信号的能力）为 5×10(17) 琼斯，在室温下的可见光和红外探测器中是报道的最高值，比商用单晶硅探测器高 4-5 个数量级。该材料是通过烧结带有氯封端的 CdTe 纳米晶制成多晶薄膜制备的，其中 Cl 选择性地在充当 n 型掺杂剂的晶界处偏析。光生电子在晶界（能量谷的网络）中浓缩并沿晶界渗滤，而空穴则局限在晶粒内部。这种静电场辅助的载流子分离和渗滤机制实现了前所未有的 10(10) 个电子/光子的光电导增益，并允许通过活性载流子猝灭来有效控制器件的响应速度。
