Today's infrared imaging devices are based on bulk and quantum-confined epitaxial materials and would benefit greatly from higher operating temperatures and lower cost. Imaging chips based on colloidal quantum dot technology could offer a convenient lower-cost alternative, but, to date, the spectral range of operation of colloidal quantum dots has been limited. In this Letter, we report colloidal HgTe quantum dot photodetectors with a room-temperature photoresponse beyond 5? ? μm, the longest interband absorption wavelength reported so far for colloidal materials. The photodetectors are fabricated from colloidal solutions, which are then drop-cast as thin films on electrodes. Operation covering the important atmospheric mid-wavelength infrared transparency window between 3 and 5? ? μm is demonstrated.
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