Improved performance of colloidal quantum dot solar cells using high-electric-dipole self-assembled layers

Azmi, Randi; Nam, So Youn; Sinaga, Septy; Oh, Seung Hwan; Ahn, Tae Kyu; Yoon, Sung Cheol; Jung, In Hwan; Jang, Sung‐Yeon

doi:10.1016/j.nanoen.2017.07.015

Cited by 32 publications

(39 citation statements)

References 42 publications

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“…With this alignment, electrons flow from the EDT-capped layers to the iodide-capped layers resulting in favorable band bending forming an electron blocking layer to prevent electron recombination at the rear metal contact. Using the same configuration, other research groups have obtained similar results using other ligand combinations with functionalities like PbI 2 and MPA [144], 1-ethyl-3-methylimidazolium iodide (EMII) and EDT [178,187,188] and 1-propyl-2,3-dimethyl-imidazolium iodide (PDMII) and 1,3-propane dithiol (PDT) [183,184]. Using PbI 2 and mercaptopropionic (MPA) ligands, Crisp et al [144] reported solar cells with thickness optimized at over 500 nm, almost double the thickness of other record-setting devices, due to favorable band alignments between the layers on the cell and improved surface passivation of PbI 2 over other halide treatments.…”

Section: Quantum Dot Solar Cellsmentioning

confidence: 75%

“…The QD absorber layer thickness in such a case is limited to the sum of the depletion width and diffusion length, which ensures that the charge carrier formed farthest away from the heterojunction can diffuse until it reaches the space charge region and then be transported to the other side of the junction by the electric field. In the following years, this depleted heterojunction QDSC configuration has undergone several modifications leading to solar cell PCE exceeding 10% [181][182][183][184][185][186][187][188][189][190][191][192][193][194][195][196][197]. The following paragraphs will detail the development of high-efficiency heterojunction QDSCs.…”

Section: Quantum Dot Solar Cellsmentioning

confidence: 99%

“…ETLs are chosen such that they passivate the surface defects present in the metal oxide layer and also promote favorable band bending at the interface between the metal oxide layer and the n type QD films that improves the built-in and open circuit voltage. These ETLs can be self-assembled monolayers (SAMs) formed by treating the metal oxide layer with organic solutions like tetrahydrofuran [184] and aminobenzoic acid [197] or other intermediate buffer layers made of materials like carbon QDs [212], CdSe QDs [214], mixed nanocrystals [188], magnesium-doped ZnO [215] or other organic buffers [216] that have given rise to devices with PCEs >9%. While all these ETLs are used in conjunction with a metal oxide layer, recently, CdS has also been successfully used as an n-type electrode instead of a metal oxide to make a heterojunction QDSC with a PCE of 8% [217].…”

Section: Quantum Dot Solar Cellsmentioning

confidence: 99%

See 2 more Smart Citations

Quantum Dot Solar Cells: Small Beginnings Have Large Impacts

2018

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From a niche field over 30 years ago, quantum dots (QDs) have developed into viable materials for many commercial optoelectronic devices. We discuss the advancements in Pb-based QD solar cells (QDSCs) from a viewpoint of the pathways an excited state can take when relaxing back to the ground state. Systematically understanding the fundamental processes occurring in QDs has led to improvements in solar cell efficiency from ~3% to over 13% in 8 years. We compile data from ~200 articles reporting functioning QDSCs to give an overview of the current limitations in the technology. We find that the open circuit voltage limits the device efficiency and propose some strategies for overcoming this limitation.

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Section: Quantum Dot Solar Cellsmentioning

confidence: 75%

Section: Quantum Dot Solar Cellsmentioning

confidence: 99%

Section: Quantum Dot Solar Cellsmentioning

confidence: 99%

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Quantum Dot Solar Cells: Small Beginnings Have Large Impacts

2018

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“…Consequently, it has become routine in literature to perform preconditioning procedures, such as exposure to air prior to photovoltaic characterization. 8,15,[20][21][22][23] However, these procedures are not standardized and a clear understanding of the evolution of the photovoltaic performance upon exposure to environmental factors has not emerged.…”

Section: Introductionmentioning

confidence: 99%

Ligand dependent oxidation dictates the performance evolution of high efficiency PbS quantum dot solar cells

Becker‐Koch

Albaladejo‐Siguan

Lami

et al. 2020

Sustainable Energy Fuels

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“…In particular, its low‐temperature solution‐processability (<150 °C) is appropriate for roll‐to‐roll printing technology on flexible substrates . However, its relatively high work function of ≈4.3 eV requires further electric dipole layers for improving the charge transporting characteristics of the CQD layers . In addition, the rough surface morphology from its crystalline structure worsens the uniform contact among the CQD and ZnO layers.…”

Section: Introductionmentioning

confidence: 99%

Improved Performance of Quantum‐Dot Photodetectors Using Cheap and Environmentally Friendly Polyethylene Glycol

Kang

Park

Jeong

et al. 2018

Adv Materials Inter

Self Cite

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there are many important applications, such as imaging and biomedical sensors, [14,15] X-ray detectors, [16] and optical communications. [17] For p-n junction QPDs, important parameters are the interfacial contact properties at the p-n junction because the internal electric field at the interfaces can decrease the trap site and charge recombination for efficient charge transport in QPDs. [18][19][20] Recently, Wei et al. reported promising photodetecting properties by developing hybrid organic/PbS CQD based QPDs. [21] The CQD layer improved the electron transport and prevented charge recombination in the devices. Thus, the bilayer contact between the bulk-heterojunction conjugated organic layer and the CQD active layer significantly decreased the dark current and improved charge collection. However, no studies were done to improve the charge collection and decrease the dark current in QPDs via modifying the interfacial properties among the CQD layer and the electron accepting layers (EALs).In this study, we have focused on the interfacial properties among CQDs and electron-accepting ZnO layers by introducing organic cathode buffer layers (CBLs) to improve the photodetecting properties of QPDs. ZnO is a well-known n-type semiconductor with high electron mobility and transmittance. [22,23] In particular, its low-temperature solution-processability (<150 °C) is appropriate for roll-to-roll printing technology on flexible substrates. [24,25] However, its relatively high work function of ≈4.3 eV requires further electric dipole layers for improving the charge transporting characteristics of the CQD layers. [26] In addition, the rough surface morphology from its crystalline structure worsens the uniform contact among the CQD and ZnO layers. To reduce the surface roughness and work function of the ZnO layer, we introduced polyethylenimine ethoxylated (PEIE) and polyethylene glycol (PEG) as the CBLs. PEIE has multiple hydroxyl side groups, which effectively generate permanent dipole moments at the interface of ZnO, and is successfully utilized in solar cells applications. [27,28] However, in the case of PEG, even though the ethylene glycol functional groups can coordinate with the ZnO layer, it has seldom been used in electronic applications to modify the EALs. [29] PEG is biologically safe, water soluble, and relatively cheap; thus, the utilization of PEG is environmentally and industrially attractive. Colloidal quantum dot (CQD) photodetectors (PDs) are developed. The on/off current ratio is improved by applying organic cathode buffer layers (CBLs), such as polyethylenimine ethoxylated (PEIE) and polyethylene glycol (PEG). The on-current of CQD-PDs (QPDs) is increased by the decreased work function of ZnO/CBLs via forming a permanent dipole moment at the interface of ZnO andCBLs. The off-current is significantly decreased by the improved interfacial morphology via softening the ZnO surfaces. In the photoconductive mode for the fast response time of a signal, PEG-and PEIE-treated QPDs exhibit improved photodetecting pro...

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Improved performance of colloidal quantum dot solar cells using high-electric-dipole self-assembled layers

Cited by 32 publications

References 42 publications

Quantum Dot Solar Cells: Small Beginnings Have Large Impacts

Quantum Dot Solar Cells: Small Beginnings Have Large Impacts

Ligand dependent oxidation dictates the performance evolution of high efficiency PbS quantum dot solar cells

Improved Performance of Quantum‐Dot Photodetectors Using Cheap and Environmentally Friendly Polyethylene Glycol

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