High performance infrared photodetectors based on CdS film activated by lanthanide-doped upconverting nanoparticles

Cadmium sulfide (CdS) semiconductors are well known due to their low cost, easy production and excellent photoelectric properties. However, the photodetectors based on CdS respond only to green light at the wavelength of 540 nm and have negligible response to infrared light. Here, we report the high performance infrared photodetectors based on CdS film activated by lanthanide doped upconverting nanoparticles. The composite film integrates a CdS semiconductor substrate with a cutting-edge photon upconversion layer comprising upconversion nanoparticles meticulously arranged within photonic crystal arrays. The CdS semiconductor substrate can respond to the green light of 540 nm, while the photon converters can efficiently convert infrared light at 980 nm to green light at 540 nm. Compared with the single CdS film, the photocurrent amplitude of the composite film is enhanced by 1302 % under the same irradiation of 980 nm infrared light, while the photoresponsivity (R) and the external quantum efficiency (EQE) are enhanced by 14 times and 140 times, respectively. This confirms that the photon up-converters play a key role for enhancing the responsibility of the CdS film to 980 nm infrared light. This finding opens a way to convert conventional semiconductor photodetectors from visible to infrared region.