Large-area semi-transparent light-sensitive nanocrystal skins

Akhavan, Shahab; Güzeltürk, Burak; Sharma, Vijay Kumar; Demir, Hilmi Volkan

doi:10.1364/oe.20.025255

Cited by 14 publications

(28 citation statements)

References 28 publications

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“…[10] Owing to the single NC layer in the device structure, noise generation is significantly reduced, enhancing the device sensitivity. These PNSs offer the potential of high sensitivity for large-area applications as they operate on the principle of photogenerated voltage buildup in the absence of an external bias.…”

Section: Introductionmentioning

confidence: 99%

Flexible and fragmentable tandem photosensitive nanocrystal skins

et al. 2016

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We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm(-2) at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.

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Section: Introductionmentioning

confidence: 99%

Flexible and fragmentable tandem photosensitive nanocrystal skins

et al. 2016

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“…In previous work, we reported that the highest possible sensitivity value for photosensitive NC skins is 104 mV under the illumination intensity of 0.175 mW/cm 2 at a 350 nm wavelength, and that their operating wavelength range is limited to 350–450 nm . Other recent work demonstrated that enhancing NC film absorption via plasmonic nanoparticles increases NC skin sensitivity .…”

Section: Introductionmentioning

confidence: 99%

“…During fabrication, the NC monolayers are dip‐coated with a computerized system on top of HfO 2 film. Synthesis of CdTe NCs and monolayer assembly procedures are all explained in detail in our previous works as well as in the experimental section here …”

Section: Introductionmentioning

confidence: 99%

Nanocrystal Skins with Exciton Funneling for Photosensing

Akhavan

Cihan

Bozok

et al. 2014

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gration atop electronic substrates (e.g., using dip coating, spin coating and drop casting), where lattice mismatch problems do not arise. Therefore, these NCs are promising candidates for applications in diverse areas, such as in light-emitting diodes, [ 3 ] solar cells, [ 4 ] and photodetectors [ 5 ] as well as for biolabeling [ 6 ] and biosensing. [ 7 ] Conventional photodetectors using NCs typically operate on the principle of collecting photogenerated charges, where an external bias must be applied for the charge collection. Although photodetectors comprising a Shockley-Schottky barrier can in principle be operated without an applied bias (in the open circuit mode), this would commonly come at the cost of decreasing the sensitivity. Recent research efforts increasingly focus on NC photodetectors that show a remarkable level of sensitivity [ 8 ] and short response times. [ 9 ] These photodetectors do, however, rely on photocurrent collection and commonly exhibit high dark current, which results in high noise levels and limits the device's detection capabilities. [ 10 ] As an alternative photosensor architecture, NC skins offer the potential of high sensitivity for large-area applications because they operate on the principle of photogenerated voltage buildup in the absence of an external bias. With a single NC layer in the device structure, noise generation is signifi cantly reduced, which enhances the device sensitivity. [

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“…These low-cost devices were initially operated on the basis of charge collection, where an electric field imposed on the detector dissociates the photogenerated excitons into electrons and holes, in which an electric current is produced [2]. On the other hand, as an alternative device structure, we have recently developed the light-sensitive nanocrystal skin (LS-NS) [3]. These LS-NS platforms, which were fabricated over areas up to 48 cm 2 , are operated on the basis of photogenerated potential buildup, as opposed to conventional charge collection.…”

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TiO<inf>2</inf> assisted sensitivity enhancement in photosensitive nanocrystal skins

Yeltik

Akhavan

Demir

2014

2014 IEEE Photonics Conference

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Solution-processable semiconductor nanocrystals (NCs) have been widely used to create novel devices for the photovoltaic, light-emission, light-detection and biosensing applications. They are good candidates especially to develope more efficient and novel optoelectronic devices owing to the high absorption cross-section, spectral tunability, deposition easiness and low cost properties. In recent years, NC integrated photodetectors have been developed to be used in large-area light-sensing applications [1]. These NC-based photodetectors have the ability to convert an optical signal to an electrical signal using the NCs as the optical absorbers. These low-cost devices were initially operated on the basis of charge collection, where an electric field imposed on the detector dissociates the photogenerated excitons into electrons and holes, in which an electric current is produced [2]. On the other hand, as an alternative device structure, we have recently developed the light-sensitive nanocrystal skin (LS-NS) [3]. These LS-NS platforms, which were fabricated over areas up to 48 cm 2 , are operated on the basis of photogenerated potential buildup, as opposed to conventional charge collection. In operation, close interaction of the monolayer NCs of the LS-NS with the top interfacing contact, while the bottom one is isolated using a high dielectric spacing layer, results in highly sensitive photosensing in the absence of external bias application. Furthermore, NC monolayer of the LS-NS makes the device semi-transparent with sufficient absorption, while reducing the noise generation and dark current. In our other recent work, we also reported that, by using a thick photoactive NC layer, a much lower photovoltage buildup was observed in the LS-NSs and it was attributed to the self-absorption effect [4]. In addition, we demonstrated the sensitivity increase in the LS-NSs via the absorption enhancement of NC film with the integration of plasmonic nanoparticles [5]. However, the localized plasmonic resonance band strongly limits the observed enhancement factor and the resultant operating wavelength range. Furthermore, in the absence of an external bias in the LS-NSs, each exciton tends to remain in the NC layer, where it was created, and recombine with the photogenerated holes that accumulate at the top interfacing contact, which causes also lower voltage buildup in the device. To overcome all these problems, in this study, we propose a thin TiO 2 layer as the electron-accepting material and demonstrate the first account of electron transfer in NC-based light-sensitive skins, which leads to significant broadband sensitivity enhancement in the active device architecture. Here, we prove that favorable conduction band offset aids in transferring photogenerated electrons from a monolayer of NCs to an electron-accepting layer, which is ultimately useful for photosensing platforms and the next generation of light-sensing NC devices.To fabricate our LS-NS devices, we first synthesized CdTe NCs in solution by using the standard pro...

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Large-area semi-transparent light-sensitive nanocrystal skins

Cited by 14 publications

References 28 publications

Flexible and fragmentable tandem photosensitive nanocrystal skins

Flexible and fragmentable tandem photosensitive nanocrystal skins

Nanocrystal Skins with Exciton Funneling for Photosensing

TiO<inf>2</inf> assisted sensitivity enhancement in photosensitive nanocrystal skins

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