Wavelength sensor as a representative optoelectronic device plays an important role in many fields including visible light communication, medical diagnosis, and image recognition. Herein, a wavelength-sensitive detector with a new...

In this study, we present a wavelength sensor that is capable of distinguishing the spectrum in the range from ultraviolet (UV) to near-infrared (NIR) light. The filterless device is composed of two horizontally stacking PdSe2/20 μm Si/PdSe2 heterojunction photodetectors with a photovoltaic (PV) behavior, which makes it possible for the device to work at 0 bias voltage. Due to the relatively small thickness of Si and the wavelength-dependent absorption coefficient, the two PdSe2/20 μm Si/PdSe2 photodetectors according to theoretical simulation display a sharp contrast in distribution of the photoabsorption rate. As a result, the photocurrents of both photodetectors evolve in completely different ways with increasing wavelengths, leading to a monotonic decrease in the photocurrent ratio from 6800 to 22 when the wavelength gradually increases from 265 to 1050 nm. The corresponding relationship between both the photocurrent ratio and wavelength can be easily described by the monotonic function, which can help to precisely determine the wavelength in the range from 265 to 1050 nm, with an average relative error less than ±1.6%. It is also revealed that by slightly revising the monotonic function, the wavelength in other different temperatures can also be estimated.

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vision, color perception in the human visual system can be predicted by using the color matching curve. Based on this, a high-resolution digital still camera was constructed using a color filter array (CFA) equipped with a charge-coupled device (CCD) to process the recognized objects and reconstruct the color images. [7] Generally, the representative wavelength sensor has been achieved by using a broadband inorganic semiconductor photodiode combined with a dichromatic prism or a set of filters. [8,9] For example, full-color sensing can be easily achieved by employing filter arrays that consist of a periodic arrangement of red, green, and blue filters. [10] This type of sensor is characterized by relatively narrow operation range (e.g., visible light). [11] As an important complement to above filter-assisted wavelength sensors, filterless sensor has lately received increasing research interest as well. [12][13][14] Although this device can quantitatively discriminate the wavelength of incident light, they are however characterized by relatively narrow sensing range and complicated device structures which entail very sophisticated instrument during device fabrication process. [15][16][17][18][19][20] Thereby, high-resolution wavelength sensor with simple device geometry is in great demand.Various study have shown that photodetectors composed of artificial nanostructures in the form of nanofilm or nanowires can exhibit unique optoelectronic characteristics. [21,22] For example, Xu et al. has recently reported that graphene/ thin Si (200 nm) heterojunction can display pronounced photoresponse to UV light illumination (365 nm), but is virtually In this paper, a broadband wavelength sensor which is composed of two horizontally stacked photodetectors is reported. The top part is a monolayer graphene (MLG)/thin Si/MLG heterojunction device and the bottom part is a MLG/Ge Schottky junction device. Owing to the thin thickness of the Si and the wavelength-dependent absorption coefficients of both Si and Ge, the two photodetectors exhibit sharp contrast in photon-generation rate when illuminated with different wavelengths of light. This distinction in photon generation leads to completely different evolution in photocurrent, and the corresponding relationship between the photocurrent ratio and wavelength can be easily expressed as a monotonic function, via which the wavelength in a broad range from deep ultraviolet (265 nm) to near infrared light (1550 nm) can be easily calculated. Notably, the average relative error and the average absolute error of the wavelength sensor are estimated to be 2.1% and 2.3 nm, respectively, which are much better than previously reported values.