FIELD OF THE INVENTION

The present invention relates the high-performance filter-free tunable spectrum photodetectors (PDs) that comprise a layer configuration of first electrode/first functional layer/second functional layer/second electrode. The filter-free tunable spectrum PDs can be used for applications in thermal imaging, thermal therapy, night-vision, light fidelity (Li-Fi), light communication, optical communication, environmental detection, agricultural, wellness, food, bioimage, automotive and security monitoring.

BACKGROUND OF THE INVENTION

Filter-free tunable spectrum PDs over different wavelength ranges, e.g., UV light, visible light, near-infrared (NIR), short-wavelength infrared, middle-wavelength infrared and long-wavelength infrared, are very useful for applications in thermal imaging, thermal therapy, night-vision, Li-Fi, light communication, optical communication, environmental detection, agricultural, wellness, food, bioimage, automotive, Li-Fi, light communication and optical communication. The present available commercial PDs are fabricated mainly using inorganic electromagnetic (EM) wave absorbing materials, such as silicon (Si) and III-V compound semiconductors, etc. These commercial PDs generally exhibit broadband photoresponsivity, e.g., from UV to infrared (IR) EM wave range. These PDs usually require an external optical filter to block the undesired EM waves outside the detection spectrum window, and thereby improving the detection spectral selectivity and sensitivity.

The filter-free tunable spectrum, e.g., the selected IR wavelength range, PDs are attractive for different IR detection applications, e.g., colorimetric measurements, Li-Fi, light communication, optical communication, light barriers, or reflective optical sensors. However, the visible light can easily disturb the detection of the IR light, as the IR PDs are usually operated in an environment with the presence of the visible light. The selected detection spectrum window for commercial IR PDs, made by Si- or III-V compound semiconductor materials, are realized by incorporating different external optical filters. The Si- and III-V compound-based PDs have some technical limitations: 1) PDs with a ˜3 μm thick active layer are often used due to the low absorption coefficient in inorganic semiconductors. 2) The use of the external optical filters reduces the overall PD sensitivity, aiding in additional device integration complexity and manufacturing cost. 3) The fabrication of these inorganic semiconductor PDs involves high processing temperature, high-energy consumption and vacuum fabrication process, and 4) they are fragile and not suitable for making flexible large area PDs. To address the above technical issues, much effort has devoted to developing highly sensitive filter-free tunable spectrum PDs using solution-processable semiconductor materials.

Solution-processable organic and hybrid semiconductors have attracted many interests for applications in filter-free PDs with tunable spectral detection of EM waves. Most solution-processable semiconducting materials have broadband absorbance, narrowband PDs are realized through device designing. The charge collection narrowing (CCN) device concept was proposed for achieving narrowband spectral detection, e.g., in red light and NIR wavelength ranges, using broadband absorbing materials. In the CCN-type PDs, a very thick light-absorbing layer, e.g., ≥2 μm, is used to deplete the photogenerated charges generated near the surface of the photoactive layer. However, the use of a thick light-absorbing layer in PDs has some drawbacks: 1) the increased material cost associated with the large material consumption and process difficulties, 2) a narrow band response of the thick PDs is realized at a cost of the reduction in the responsivity as compared to the thin film type PDs, 3) PDs with a thick light-absorbing layer reduces the response speed. A microcavity PD is used to obtain narrow band detection with limited responsivity and high angular dependent photoresponses. Microcavity PDs are also used for NIR detection, where a highly reflective distributed Bragg reflector (DBR) is used to form a wavelength selective resonant cavity. Microcavity PDs with a DBR reflector have a typical narrowband photodetection in the NIR wavelength range, with a full width at half maximum (FWHM) of <20 nm. However, the fabrication of the DBR reflector requires a precise wavelength matching condition and costly process. The microcavity configuration PD is highly angular dependent and has limitations for realizing filter-free tunable spectrum PDs.

Definition

The following abbreviations used herein refer to their corresponding chemical name or equivalents which a skilled artisan would use to define as such:

P3HT: poly(3-hexylthiophene-2,5-diyl)

PBDB-T: poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)]

PDPP3T: poly{2,2′-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5′-diyl-alt-thiophen-2,5-diyl}

m-ITIC: 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene

PTB7-Th: poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]

COi8DFIC: 2,2′-[[4,4,11,11-tetrakis(4-hexylphenyl)-4,11 dihydrothieno[2′,3′:4,5]thieno[2,3-d]thieno[2″″,3″″:4″′,5″′]thieno[2″′,3″′:4″,5″]pyrano[2″,3″:4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]pyran-2,9-diyl]bis[methylidyne(5,6-difluoro

PC70BM: [6,6]-Phenyl-C71-butyric acid methyl ester

PCPDTBT: poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]

Full name of some blends described herein are as follows:

PBDB-T:m-ITIC: poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)]:poly {2,2′-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5′-diyl-alt-thiophen-2,5-diyl}

PDPP3T:m-ITIC: poly{2,2′-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5′-diyl-alt-thiophen-2,5-diyl}:3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene

PTB7-Th:COi8DFIC:PC70BM: poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]:2,2′-[[4,4,11,11-tetrakis(4-hexylphenyl)-4,11-dihydrothieno[2′,3′:4,5]thieno[2,3-d]thieno[2″″,3″″:4″′,5′″]thieno[2″′,3′″:4″,5″]pyrano[2″,3″:4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]pyran-2,9-diyl]bis[methylidyne(5,6-difluoro:[6,6]-Phenyl-C71-butyric acid methyl ester

PTB7-Th:PC70BM: poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]:[6,6]-Phenyl-C71-butyric acid methyl ester

PCPDTBT:PC70BM: poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]:[6,6]-Phenyl-C71-butyric acid methyl ester

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a high-performance filter-free tunable spectrum PDs comprising a layered structure of at least two electrodes and at least two functional layers, e.g., an assembly of first electrode/first functional layer/second functional layer/second electrode. The first electrode being more proximal to an incident light can be a transparent or a semi-transparent conductive layer with appropriate surface electronic properties that are suitable for charge extraction at the first electrode/first functional layer interface. The second electrode being more distal to the incident light can be a transparent, semi-transparent or an opaque conductive layer with appropriate surface electronic properties that are suitable for charge extraction at the second functional layer/second electrode interface. The first functional layer serves as a shorter-wavelength EM wave, selected over the wavelength range from 10 nm to 1000 μm, depletion layer, which can be a layer or a stack of inorganic semiconductors, or an organic semiconductor, or an organic/polymer donor/acceptor blend, or a hybrid semiconductor or their combinations that has a good charge transport property. The second functional layer can be a functional layer or a stack of functional layers or heterojunctions or a combination of functional layers and bulk heterojunctions absorbing the longer-wavelength EM waves selected over the wavelength range from 10 nm to 1000 μm. The filter-free tunable spectral detection is realized by adjusting the selected spectral response window within the afore-mentioned wavelength range, determined by the difference in wavelengths between the transmission cut-off wavelength of the first functional layer and the absorbing edge of the second functional layer.

In an embodiment, the first functional layer and the second functional layer are made of materials comprising organic, polymer, perovskite, colloidal quantum dots, and inorganic compounds, or any combination thereof.

In another embodiment, the shorter-wavelength EM wave depletion layer is selected from a P3HT layer, a PTB7-Th layer, a CH3NH3Pb0.5Sn0.5I3perovskite layer or a CH3NH3PbI3perovskite layer.

In other embodiment, the longer-wavelength EM wave absorbing layer is selected from a PBDB-T:m-ITIC blended layer, a PDPP3T:m-ITIC blended layer, PTB7-Th:COi8DFIC:PC70BM blended layer, a PTB7-Th:PC70BM blended layer or a PCPDTBT:PC70BM blended layer.

In yet another embodiment, the photodetector is prepared by using solution fabrication, vacuum evaporation, printing processes, nanoimprinting, transfer processes, or any combination thereof.

In a further embodiment, the first functional layer can also be an absorption layer for absorbing the shorter-wavelength EM waves.

In other embodiment, the second functional layer is an absorption layer for absorbing the longer-wavelength EM waves.

In an embodiment, the at least two electrodes comprise transparent conducting oxides, thin metal layer, conducting polymers, organic semiconductors, nanostructured transparent electrode, metal nanoparticles, metal nanowires, graphene sheets, or any combination thereof.

In another embodiment, the first electrode is selected from a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) layer, an indium tin oxide (ITO) layer, a surface modified PEDOT:PSS layer or a surface modified ITO layer; the second electrode is from an aluminum (Al) layer, silver (Ag) layer, zinc oxide (ZnO)-modified Al layer or ZnO-modified Ag layer.

In yet another embodiment, the layered structure further comprises an interlayer sandwiched between a first functional layer and a second functional layer of the at least two functional layers.

In other embodiment, the interlayer comprised in the layered structure is configured to assist charge exchange and comprising conducting polymer, metal oxide, self-assembled monolayer, metal nanoparticles, metal nanowires, graphene sheets, or any combination thereof.

The present photodetector has a photoresponse to a selected spectrum window within a wavelength range from 10 nm to 1000 μm and is operable with or without bias.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described.

The present invention includes all such variation and modifications. The invention also includes all the steps and features referred to or indicated in the specification, individually or collectively, and any and all combination or any two or more of the steps or features.

Other aspects and advantages of the present invention will be apparent to those skilled in the art from a review of the ensuing description.

