infancy. For a photodetector that exhibits linear dichroism, the key figure-of-merit is the polarization sensitivity, which is usually repre- sented by the dichroic ratio (DR) of maximum to minimum polarization-dependent photoresponse. However, in most cases, the obtained DRs were at a low level of <10 (ref. 15–17, 20–25), which were fundamentally limited by the inherent anisotropy of photoactive materials and further weakened by the severe charge carrier recom- bination in photoconductors. In light of this, a few works have incor- porated anisotropic materials into heterostructures to effectively separate the photogenerated charge carriers, thereby leading to enhanced DRs of ~102 (ref. 26, 27). More recently, much improved polarization sensitivity has been further demonstrated by virtue of ferroelectrics or an external amplification circuitry28,29. Nonetheless, an effective and general strategy for anisotropic photocurrent amplifi- cation in single-component photodetectors remains elusive thus far, posing fundamental constraints to the promotion of simplified on-chip polarimetry. In this study, we proposed a simple yet general anisotropic pho- tocurrent amplification strategy to boost the polarization sensitivity of single-component phototransistors. Theoretical estimations unv
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Anisotropic charge trapping in phototransistors unlocks ultrasensitive polarimetry for bionic navigation
Jing Pan, Yiming Wu, Xiujuan Zhang, Jinhui Chen, Jinwen Wang, Shuiling Cheng, Xiaofeng Wu, Xiaohong Zhang, Jiansheng Jie
Research context
Abstract Being able to probe the polarization states of light is crucial for applications from medical diagnostics and intelligent recognition to information encryption and bio-inspired navigation. Current state-of-the-art polarimeters based on anisotropic semiconductors enable direct linear dichroism photodetection without the need for bulky and complex external optics. However, their polarization sensitivity is restricted by the inherent optical anisotropy, leading to low dichroic ratios of typically smaller than ten. Here, we unveil an effective and general strategy to achieve more than 2,000-fold enhanced polarization sensitivity by exploiting an anisotropic charge trapping effect in organic phototransistors. The polarization-dependent trapping of photogenerated charge carriers provides an anisotropic photo-induced gate bias for current amplification, which has resulted in a record-high dichroic ratio of >10 4 , reaching over the extinction ratios of commercial polarizers. These findings further enable the demonstration of an on-chip polarizer-free bionic celestial compass for skylight-based polarization navigation. Our results offer a fundamental design principle and an effect
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Jing Pan, Yiming Wu, Xiujuan Zhang, Jinhui Chen, Jinwen Wang, Shuiling Cheng, Xiaofeng Wu, Xiaohong Zhang, Jiansheng Jie. Anisotropic charge trapping in phototransistors unlocks ultrasensitive polarimetry for bionic navigation. Nature Communications (2022). https://doi.org/10.1038/s41467-022-34421-3
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