Unraveling the Gain Mechanism in High Performance Solution‐Processed PbS Infrared PIN Photodiodes

Lee, Jae Woong; Kim, Do Young; So, Franky

doi:10.1002/adfm.201403673

Cited by 81 publications

(79 citation statements)

References 35 publications

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“…Under such conditions devices can exhibit gain at high electric fields provided that the electrodes facilitate the replenishment of the extracted carriers. Gain mechanisms have now also been exploited in photodiode devices [36][37][38][39] (where trap rich materials are deliberately introduced in the photoactive region) or by creating heterostructure configurations in order to trap one charge carrier type.…”

Section: Restricting Attention To Recombination Centersmentioning

confidence: 99%

“…2f. 79,80 These devices incorporate both electron and hole blocking layers to supress charge injection from the conducting electrodes. In the case of 1, 3-benzedithiol (BDT) treated PbS NCs the Fermi level lies close to the middle of the PbS bandgap, therefore these PbS NCs are treated as an intrinsic semiconductor sandwiched between p-type and n-type materials.…”

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Lead sulphide nanocrystal photodetector technologies

2016

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2 Few other areas of study have uncovered the secrets of the universe like that of the interaction between light and matter, leading to many revolutionary scientific discoveries. The interaction of light, in particular with semiconducting materials, has enabled us to understand the behaviour of various fundamental phenomena and has laid the foundation of the optoelectronic systems that we rely on today. The majority of such systems necessitate the detection of light which is achieved via the use of photodetector devices. A photodetector converts incident photons into an electrical signal, which in the solid-state, is assembled together with an application-oriented readout integrated circuit (ROIC). Present-day commercially available photodetectors are typically made from gallium phosphide/silicon carbide (GaP)/(SiC), silicon (Si) and indium gallium arsenide/germanium (InGaAs)/(Ge) for detection in the ultraviolet (UV), visible and near-infrared (IR) regimes of the electromagnetic spectrum, respectively. For mid and far IR, lead sulphide (PbS), lead selenide (PbSe), indium antimonide (InSb), indium arsenide (InAs) and mercury cadmium telluride (HgCdTe) based photodetectors are commonly used. Photodetectors based on a photoemissive principle such as photomultiplier tubes (PMTs) are also widely used for ultrasensitive detection in the UV to near-IR spectral regime and are fabricated using alkali metals having a low workfunction. For applications demanding multispectral detection, 'two-colour' detectors are often manufactured with a bi-level structure, for example consisting of an IR transmitting Si photodiode mounted over an IR sensitive PbS photoconductor. Such a device structure has drawbacks that include added cost, increased complexity of device fabrication and associated issues in implementation. Furthermore, a significant majority of applications are based upon UV to near-IR light detection where the indirect bandgap of Si, the InGaAs epitaxial growth process, PMT bulkiness and high bias voltage requirement all present challenges and renders their use with flexible platforms impossible. As a result significant research effort continues to be expended on the development of a singlesystem multispectral photodetector to replace two or more detectors. In the last decade amongst all the candidate materials studied 1 PbS semiconductor nanocrystals (NCs), often referred as 'quantum dots', have emerged as the most promising material for the fabrication of 3 this type of photodetector. Such has been the progress in their development that reported PbS NC based photodetectors have already outperformed conventional state-of-the-art photodetectors in many aspects including low-cost room temperature device fabrication via solution processing, flexible substrate compatibility, broadband spectral sensitivity along with the figures of merit achieved, Fig 1a. In this review article, we present an overview of recent developments in PbS NC based photodetectors. We first provide a brief introduction to PbS NCs and their releva...

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Section: Restricting Attention To Recombination Centersmentioning

confidence: 99%

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confidence: 99%

Lead sulphide nanocrystal photodetector technologies

2016

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“…[1][2][3] Recent years have witnessed numerous organic and organic/inorganic hybrid photodetectors with wide response spectrum, [4][5][6][7] high external quantum effi ciency (EQE), [7][8][9][10][11][12] low dark current density, [ 4,[13][14][15] as well as fast response time, [ 16,17 ] fabricated either by vacuum evaporation or solution processing.…”

Section: Doi: 101002/adom201500224mentioning

confidence: 99%

Extremely Low Dark Current, High Responsivity, All‐Polymer Photodetectors with Spectral Response from 300 nm to 1000 nm

Zhou

Yang

2015

Advanced Optical Materials

130

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COMMUNICATIONbetter organic photodetector performance could be achieved if a low dark current density and a high EQE can be reached at the same time.In this paper, we present the fabrication and characterization of an all polymer photodetector sensing from 300 nm to 1000 nm with a calculated peak detectivity greater than 1.0 × 10 13 Jones in the NIR region, on the basis of the shot noise limit. The device also shows a respectable EQE of 27.7% at a wavelength of 850 nm under −0.5 V bias. Importantly, the dark current density is as extremely low as 0.64 nA cm −2 , which should be the best result among all wide spectrum response organic photodetectors reported so far. It can be seen that introducing a thin cross-linkable hole transporting/electron blocking layer greatly reduces the dark current density, while simultaneously preserving the photoresponse.A low-bandgap diketopyrrolopyrrole (DPP)-based polymer poly(diketopyrrolopyrrole-terthiophene) (PDPP3T), as shown in Figure 1 a, is utilized as the donor material, which has proven to be a promising candidate for organic fi eld-effect transistors (OFETs) and organic solar cells. [21][22][23][24] This polymer possesses a narrow-bandgap of 1.3 eV and nearly balanced hole and electron mobilities of 0.04 and 0.01 cm 2 V −1 s −1 . [ 21 ] As shown, it is able to cover the UV/visible/NIR spectral region and outputs a high photoresponse when incorporated with a (6,6)-phenyl-C71-butyric acid methyl ester (PC 71 BM) acceptor.Poly[ N , N ′-bis(4-butylphenyl)-N , N ′-bis(phenyl)-benzidine] (poly-TPD) is an effi cient hole transport material with a hole mobility of about 2.0 × 10 −3 cm 2 V −1 s −1 and has been widely used in polymer/quantum dot light emitting diodes as hole transporting layer due to its resistance to nonpolar organic solvents, such as toluene and p-xylene. [25][26][27] As reported, poly-TPD is also cross-linkable under 254 nm UV light exposure, [ 28 ] which is favorable to multilayer solution processing even with polar solvent, such as chloroform (CF) and o-dichlorobenzene ( o-DCB). In our devices, the cross-linked polymer is used as a buffer layer to collect the photogenerated holes and block the electron injection from the indium tin oxide (ITO) anode to the active layer under reverse bias.To verify the resistance of cross-linked poly-TPD fi lm to polar solvent, the absorption measurements were carried out for the poly-TPD fi lms deposited on fused silica substrates, both with and without UV irradiation. Prior to testing, the fi lms were washed by spin coating with o-DCB solvent and then dried on a hotplate. As shown in Figure 2 , after washing, the absorption remains as high as 92% for the UV light treated fi lm, while the value for the untreated fi lm is only 9.7%. The results suggest that poly-TPD fi lm gets cross-linked and shows excellent polar solvent resistivity after UV light exposure.

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“…Various PbS nanocomposites have been reported to enhance the photovoltaics and photodetection performance of PbS. These PbS nanocomposites include: PbS nanocomposites with organic compounds such as conjugated polymers [7], semiconducting polymer [8][9][10], poly(amidoamine) dendrimer [11], PbS nanocomposites with fullerene or fullerene derivatives [12][13][14], hybrid graphene-PbS quantum dots [15,16], PbS nanocomposites with metal nanoparticles such as Ag, Au [17][18][19], PbS quantum dots/TiO 2 heterojunction [20][21][22], PbS quantum dots/ZnO heterojunction [23][24][25][26][27]. In principle, improving e-h efficiency through the formation of PbS nanocomposites not only depends on their energy level alignment, but also depends on the interface structure of PbS nanocomposites as the migration of charger carriers occurs at the interface.…”

Section: Introductionmentioning

confidence: 99%

“…The conduction band edge and valence band edge of ZnO are lower than the corresponding that of narrow band PbS. Thus, PbS/ZnO nanocomposite has a favorable energy level alignment, and the charge separation at the heterojunction interface is energetically favorable [23][24][25][26][27]. However, up to now, there has been few report about the effect of the PbS/ZnO interface on the photodetection performance.…”

Section: Introductionmentioning

confidence: 99%