Near-infrared and visible light dual-mode organic photodetectors

Abstract

We report a dual-mode organic photodetector (OPD) that has a trilayer visible light absorber/optical spacer/near-infrared (NIR) light absorber configuration. In the presence of NIR light, photocurrent is produced in the NIR light–absorbing layer due to the trap-assisted charge injection at the organic/cathode interface at a reverse bias. In the presence of visible light, photocurrent is produced in the visible light–absorbing layer, enabled by the trap-assisted charge injection at the anode/organic interface at a forward bias. A high responsivity of >10 A/W is obtained in both short and long wavelengths. The dual-mode OPD exhibits an NIR light response operated at a reverse bias and a visible light response operated at a forward bias, with a high specific detectivity of ~1013 Jones in both NIR and visible light ranges. A bias-switchable spectral response OPD offers an attractive option for applications in environmental pollution detection, bioimaging process, wellness, and security monitoring in two distinct bands.

Stacked Dual‐Wavelength Near‐Infrared Organic Photodetectors

“…To further miniaturize these sensors, it is desirable to detect and distinguish several wavelengths via a single detecting surface. [ 17,18 ] Hereby, the accuracy of substance identification improves with the number of wavelengths detected. For example, signal ratios for two wavelengths will be independent of the incident light intensity.…”

Vacuum‐Processed Small Molecule Organic Photodetectors with Low Dark Current Density and Strong Response to Near‐Infrared Wavelength

“…For example, Equation (1) assumes that the total noises of the photodetector are dominated by shot noise in I dark , which means that the shot noise level must be several times or even an order of magnitude higher than that of the Johnson (thermal) noise. [52] The R SH of proposed OPDs with active layer thicknesses of 20, 40, 60, and 80 nm are 0.78, 1.18, 1.23, and 1.47 MΩ, respectively. Based on the results of I dark and R SH , the calculated i shot near zero bias shows twice of magnitude lower than the thermal noise (see Table S1, Supporting Information).…”

“…Specific detectivity, D*, of a photodetector determines its ability to detect the weakest photosignal under various noises such as shot, Johnson (thermal), and flicker (1/f). [12,19,22,[49][50][51][52][53][54] D* is a crucial figure of merit for photodetectors, which is usually expressed in the simple equation by [8][9][10][11][12][13][14][15][16][17][18]21,22,38,52,54,55]…”

“…In principle, J dark is the sum of total noise, including the shot noise, thermal (Johnson) noise, and flicker noise (1/f). Generally, the flicker noise is negligible at frequencies beyond 100 Hz [51] while the shot noise (i shot ) and thermal noise (i thermal ) could be estimated by following [52]…”

“…The response of the OPD device under various intensities of light was studied by measuring the linear dynamic range (LDR), which is expressed as the ratio of the strongest to the weakest optical power (irradiance) when the device maintains its linear response. [20,49] Figure 7 depicts the LDR plots of the OPD devices which are exposed to radiance from laser and LED at a bias voltage of −2 V. The LDR (dB) of OPD device was calculated by using Equation (5) [5,14,15,[20][21][22]31,52,55,56] J J…”