Abstract:Solution processable near infrared (NIR) photodetectors provide a promising alternative due to their low cost, flexible design, adaptability to various fabrications, and large area manufacturability, removing the limitations of traditional wafer-based inorganic semiconductor techniques. High performing NIR photodetectors offer attractive options for applications in visualizing NIR light, health and safety monitoring.
“…Organic photodetectors (OPDs) are a promising alternative optical detecting technology to conventional inorganic counterparts because the optical and electric properties of organic semiconducting materials can be tailored accordingly (1). They offer additional advantages such as having a solution-processable fabrication process, which also leads to substantial cost-benefits, thereby creating next-generation solution-processable, flexible, and low-cost photodetectors (2). In general, the spectral responses of the photodetectors are determined by the absorption of the active materials and optical profile in the devices (3).…”
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.
“…Organic photodetectors (OPDs) are a promising alternative optical detecting technology to conventional inorganic counterparts because the optical and electric properties of organic semiconducting materials can be tailored accordingly (1). They offer additional advantages such as having a solution-processable fabrication process, which also leads to substantial cost-benefits, thereby creating next-generation solution-processable, flexible, and low-cost photodetectors (2). In general, the spectral responses of the photodetectors are determined by the absorption of the active materials and optical profile in the devices (3).…”
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.
“…The photoresponsivity ( R ), detectivity ( D * ), and EQE of the photodiodes were estimated from the J–V curves in Fig. 3 using the following equations 2 , 3 : Figure 4 ( a ) Photocurrent ( I ph ) as a function of the light intensity ( P IN ) under NIR wavelength illumination of 980 nm at 0 V and − 0.4 V. ( b , c ) Responsivity ( R ), detectivity ( D * ), and EQE as functions of the light intensity ( P IN ) under NIR wavelength illumination of 980 nm at ( b ) 0 V and ( c ) − 0.4 V. ( d , e ) Schematic energy band diagrams of solCIGS and K-solCIGS photodiodes at low light intensity under ( d ) 0 V and ( e ) − 0.4 V (reverse bias condition). At 0 V, tunneling of hole does not occur.…”
Although solution-processed Cu(In,Ga)(S,Se)2 (CIGS) absorber layers can potentially enable the low-cost and large-area production of highly stable electronic devices, they have rarely been applied in photodetector applications. In this work, we present a near-infrared photodetector functioning at 980 nm based on solution-processed CIGS with a potassium-induced bandgap grading structure and chalcopyrite grain growth. The incorporation of potassium in the CIGS film promotes Se uptake in the bulk of the film during the chalcogenization process, resulting in a bandgap grading structure with a wide space charge region that allows improved light absorption in the near-infrared region and charge carrier separation. Also, increasing the Se penetration in the potassium-incorporated CIGS film leads to the enhancement of chalcopyrite crystalline grain growth, increasing charge carrier mobility. Under the reverse bias condition, associated with hole tunneling from the ZnO interlayer, the increasing carrier mobility of potassium-incorporated CIGS photodetector improved photosensitivity and particularly external quantum efficiency more than 100% at low light intensity. The responsivity and detectivity of the potassium-incorporated CIGS photodetector reach 1.87 A W−1 and 6.45 $$\times$$
×
1010 Jones, respectively, and the − 3 dB bandwidth of the device extends to 10.5 kHz under 980 nm near-infrared light.
“…[17,20,21] In contrast, organic photodetectors offer the potential of low-cost manufacturing, facile processing methods, light weight forms, high flexibility, and large-area scalability, while also providing tunable bandgaps, high quantum efficiency, and high sensitivity, thus making them promising alternatives to current commercial devices. [18,20,22] Current approaches to organic NIR photodetectors include photoconductor, [21,22] photodiode, [17][18][19][20][21][22][23] and phototransistor [21,23] devices (Figure 1), of which photodiodes were the first to be developed and are still the most commonly studied. In addition, photodetectors can be classified as broadband (panchromatic) or narrowband (wavelength selective), depending on the width of their spectral response window.…”
Advances in the synthesis of low bandgap (Eg < 1.5 eV) conjugated polymers has produced organic materials capable of absorbing near-infrared (NIR) light (800-2500 nm), with these materials first applied to photodiode NIR detectors in 2007 as an alternative to more traditional inorganic devices. Although the development of organic NIR photodetectors has continued to advance, their ability to effectively detect wavelengths in the low-energy portion of the NIR spectrum is still limited. Efforts to date concerning the production of photodiode-based devices capable of detecting light beyond 1000 nm are reviewed.
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