Ultrasensitive Colloidal Quantum-Dot Upconverters for Extended Short-Wave Infrared.

Infrared-to-visible upconverters converting low-energy infrared to higher-energy visible light without bringing in complicated readout integrated circuits have triggered enormous excitement. However, existing upconverters suffer from limited sensing wavelengths, low photon-to-photon (p-p) efficiency, and high minimum detectable infrared power. Here, we reported the colloidal quantum-dot (CQD) upconverters with unprecedented performance. By using HgTe CQDs as the sensing layer, the operation spectral ranges of the upconverters are, for the first time, extended to short-wave infrared. More importantly, the resistance-area products of the HgTe CQD photodetectors are carefully optimized by interface engineering to match with the visible light-emitting diodes so that the quantum efficiency and sensitivity of upconverters can be maximized. The integrated upconverters demonstrate a high p-p efficiency of nearly 30% and a low detection limit down to 20 μW cm.