Chemical processing of three-dimensional graphene networks on transparent conducting electrodes for depleted-heterojunction quantum dot solar cells

Tavakoli, Mohammad Mahdi; Simchi, A.; Fan, Zhiyong; Aashuri, Hossein

doi:10.1039/c5cc06955f

Cited by 42 publications

(37 citation statements)

References 20 publications

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“…1) the formation of ZnOC bonds after chemisorption of Zn 2+ ions on the surface of the embryonic ZnO QDs and reaction with GO functional groups, and 2) the reaction of Zn 2+ ions with GO to establish ZnO bonds and combine with embryonic ZnO QDs. The layer‐by‐layer chemical exfoliation process of GO nanosheets occurs during these reactions and ZnO QDs are wrapped with rGO as a hybrid structure …”

Section: Resultsmentioning

confidence: 99%

“…In these hybrid nanostructures, graphene is an efficient and fast charge extraction layer . In our previous works, we fabricated hybrid nanostructures of PbS quantum dots (QDs) and graphene and employed them as an absorber layer in quantum dot solar cells and improved the performance of the device by up to 40% . Wang et al also demonstrated that the hybrid nanostructure of graphene and TiO 2 NPs can improve the device performance of a perovskite solar cell up to 15.6%.…”

Section: Introductionmentioning

confidence: 99%

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High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer

Tavakoli

Nourbakhsh

et al. 2016

Adv Materials Inter

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power conversion effi ciency (PCE) more than 20% has been achieved using a solution process. [6][7][8][9][10] Among the different processes for fabrication of perovskite solar cells, including one-step solution process, [ 11,12 ] sequential deposition, [ 13,14 ] vacuum deposition, [ 15 ] and chemical vapor deposition, [ 16 ] a two-step solution process has benefi ts such as good control of the crystal structure for perovskite fi lm. [ 17 ] In order to fabricate perovskite solar cells, different types of electron transfer layers (ETLs) and hole transfer layers (HTLs) have been employed. Among them, a conducting polymer such as poly(3,4-ethylenedioxythiophene):polystyr enesulfonate (PEDOT:PSS) is commonly used as the HTL in perovskite solar cells. However, the high acidity of this polymer deteriorates the ITO layer, and its high hygroscopicity can also accelerate degradation of the device due to water absorption. [ 18 ] Recently, many research groups have focused on inorganic materials that can work as an HTL, such as CuSCN and NiO. [19][20][21] Regarding the ETL materials, more stable metal oxides, such as titanium dioxide (TiO 2 ), zinc oxide (ZnO), and tin oxide (SnO 2 ) have been developed for perovskite solar cells. [ 22 ] Among these metal oxides, TiO 2 -nanoparticles (NPs) have been commonly used as the ETL to provide an effi cient charge collection. [ 23 ] In order to prepare a TiO 2 mesoporous layer, a sintering process with high temperature (≈500 °C) is required. [ 18 ] This temperature is too high for fabrication of perovskite on plastic substrate. In addition, few groups already have reported ETL-free perovskite solar cell with descent PCE on plastic substrates; however, their PCE is not comparable with those devices fabricated on rigid substrates.ZnO NPs are, therefore, a promising candidate to replace TiO 2 NPs as the ETL layer in perovskite solar cells. However, only a few works have reported perovskite solar cells based on ZnO NPs. Intriguingly, the devices on ZnO NPs show a maximum PCE of close to 15.7%, [ 24 ] which is lower than those on TiO 2 NPs. To fabricate the device on ZnO NPs, a twostep solution process is usually employed. Depending on the annealing temperature (70 °C-100 °C) of the perovskite fi lm, different works have reported a device performance from 8.9% to 15.7%. [24][25][26][27] In addition, a few works have demonstrated the instability of perovskite materials on top of ZnO NPs due to Fabrication of organohalide perovskite materials on the top of ZnO nanoparticles (NPs) has some benefi cial advantages such as room temperature processing; however, the perovskite is not stable on ZnO NPs layer during the annealing process. In fact, there are only a few reports about the fabrication of perovskite solar cells on ZnO NPs layer. Herein, the decomposition mechanism of CH 3 NH 3 PbI 3 perovskite materials on ZnO is reported, and it is found that the perovskite fi lm on the top of the ZnO layer is converted into PbI 2 during the annealing process due to the existence of hydroxide groups on...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer

Tavakoli

Nourbakhsh

et al. 2016

Adv Materials Inter

Self Cite

150

123

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show abstract

“…Therefore, nanostructures can not only improve optical absorption, but also simultaneously shorten the photo-generated carrier collection length and result in more effective carrier collection. [33][34][35][36] Radial p-n junctions and nanostructured electrodes, in particular, have been proven effective for the aforementioned purposes. Nonetheless, much literature has reported that the proper design of solar energy harvesting devices is of utmost importance and optimizations of different key aspects are needed.…”

Section: Introductionmentioning

confidence: 99%

Progress and Design Concerns of Nanostructured Solar Energy Harvesting Devices

Leung

Zhang

Tavakoli

et al. 2016

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Integrating devices with nanostructures is considered a promising strategy to improve the performance of solar energy harvesting devices such as photovoltaic (PV) devices and photo-electrochemical (PEC) solar water splitting devices. Extensive efforts have been exerted to improve the power conversion efficiencies (PCE) of such devices by utilizing novel nanostructures to revolutionize device structural designs. The thicknesses of light absorber and material consumption can be substantially reduced because of light trapping with nanostructures. Meanwhile, the utilization of nanostructures can also result in more effective carrier collection by shortening the photogenerated carrier collection path length. Nevertheless, performance optimization of nanostructured solar energy harvesting devices requires a rational design of various aspects of the nanostructures, such as their shape, aspect ratio, periodicity, etc. Without this, the utilization of nanostructures can lead to compromised device performance as the incorporation of these structures can result in defects and additional carrier recombination. The design guidelines of solar energy harvesting devices are summarized, including thin film non-uniformity on nanostructures, surface recombination, parasitic absorption, and the importance of uniform distribution of photo-generated carriers. A systematic view of the design concerns will assist better understanding of device physics and benefit the fabrication of high performance devices in the future.

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“…28 Graphene (Gr), a single-layer of carbon sheet, exhibits excellent electronic conductivity [29][30][31] and optical transmittance [32][33][34] with great potential to replace metals as transparent electrodes. [35][36][37][38][39][40][41][42] Gr/Si structures have been studied in solar cells, 36,38,39 as well as, visible and INR photodetectors, 41,[43][44][45][46][47][48] showing excellent performances. Ultra-shallow (essentially, zero X J ) Gr/Si Schottky structure could be more suitable for UV detection, because it not only resolves the serious surface recombination due to the shallow junction satisfying the UV light penetration depth in Si, but also simplifies the fabrication process to reduce the cost.…”

Section: Introductionmentioning

confidence: 99%

A self-powered high-performance graphene/silicon ultraviolet photodetector with ultra-shallow junction: breaking the limit of silicon?

et al. 2017

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We present a self-powered, high-performance graphene-enhanced ultraviolet silicon Schottky photodetector. Different from traditional transparent electrodes, such as indium tin oxides or ultra-thin metals, the unique ultraviolet absorption property of graphene leads to long carrier life time of hot electrons that can contribute to the photocurrent or potential carrier-multiplication. Our proposed structure boosts the internal quantum efficiency over 100%, approaching the upper-limit of silicon-based ultraviolet photodetector. In the near-ultraviolet and mid-ultraviolet spectral region, the proposed ultraviolet photodetector exhibits high performance at zero-biasing (self-powered) mode, including high photo-responsivity (0.2 A W −1 ), fast time response (5 ns), high specific detectivity (1.6 × 10 13 Jones), and internal quantum efficiency greater than 100%. Further, the photo-responsivity is larger than 0.14 A W −1 in wavelength range from 200 to 400 nm, comparable to that of state-of-the-art Si, GaN, SiC Schottky photodetectors. The photodetectors exhibit stable operations in the ambient condition even 2 years after fabrication, showing great potential in practical applications, such as wearable devices, communication, and "dissipation-less" remote sensor networks.

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Chemical processing of three-dimensional graphene networks on transparent conducting electrodes for depleted-heterojunction quantum dot solar cells

Cited by 42 publications

References 20 publications

High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer

High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer

Progress and Design Concerns of Nanostructured Solar Energy Harvesting Devices

A self-powered high-performance graphene/silicon ultraviolet photodetector with ultra-shallow junction: breaking the limit of silicon?

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