A hydro/oxo-phobic top hole-selective layer for efficient and stable colloidal quantum dot solar cells

Baek, Se Woong; Lee, Sang Hoon; Song, Jee-Hun; Kim, Changjo; Ha, Ye-Seol; Shin, Hyungcheol; Kim, Hyungjun; Jeong, Sohee; Lee, Jung‐Yong

doi:10.1039/c7ee03184j

Cited by 41 publications

(38 citation statements)

References 32 publications

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“…Recent advances in CQD PV have relied on lead iodide (PbI 2 ) passivated CQD solids fabricated using solution‐based ligand exchanges, with devices retaining 90% of their initial performance following air storage for 1000 h . With the additional help of hydro/oxo‐phobic hole transporting materials, the air stability retained over 90% of initial performance following 1 year of ambient air storage . Cao et al reported that CQD PV devices retain 80% of their initial efficiency following 1000 h of continuous light illumination under N 2 atmosphere …”

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confidence: 99%

Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

Choi

Kim

et al. 2020

Advanced Materials

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Colloidal quantum dots (CQDs) are promising materials for photovoltaic (PV) applications owing to their size‐tunable bandgap and solution processing. However, reports on CQD PV stability have been limited so far to storage in the dark; or operation illuminated, but under an inert atmosphere. CQD PV devices that are stable under continuous operation in air have yet to be demonstrated—a limitation that is shown here to arise due to rapid oxidation of both CQDs and surface passivation. Here, a stable CQD PV device under continuous operation in air is demonstrated by introducing additional potassium iodide (KI) on the CQD surface that acts as a shielding layer and thus stands in the way of oxidation of the CQD surface. The devices (unencapsulated) retain >80% of their initial efficiency following 300 h of continuous operation in air, whereas CQD PV devices without KI lose the amount of performance within just 21 h. KI shielding also provides improved surface passivation and, as a result, a higher power conversion efficiency (PCE) of 12.6% compared with 11.4% for control devices.

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confidence: 99%

Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

Choi

Kim

et al. 2020

Advanced Materials

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“…An ideal HTL in PbS CQD‐SCs should combine appropriate energy levels to allow efficient hole‐extraction and electron‐blocking; [ 7 ] sufficient hole mobility for efficient vertical charge transport; [ 8 ] a diffusion length enabling contribution to the device photocurrent; [ 9 ] materials processing that is compatible with underlying layers in the CQD device; [ 10 ] and excellent morphology and conformal coverage to prevent oxygen and moisture permeation. [ 11 ]…”

Section: Figurementioning

confidence: 99%

A Tuned Alternating D–A Copolymer Hole‐Transport Layer Enables Colloidal Quantum Dot Solar Cells with Superior Fill Factor and Efficiency

et al. 2020

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Colloidal quantum dot solar cells (CQD-SCs) are attractive in view of their wide optoelectronic tunability and manufacturing benefits. [1] The power conversion efficiency (PCE) of CQD-SCs has seen rapid advances over the past decade, reaching a PCE of 13.3% through improvements in CQD surface chemistry and device architecture. [2] To date, the most efficient CQD-SCs consist (Figure 1a) of a thin electron transport/hole-blocking layer of zinc oxide deposited on indium-tin-oxide; an active layer, comprising a CQD solid passivated using halide atoms; and a thin hole-transport layer (HTL) of CQDs cross-linked with 1,2-ethanedithiol (EDT). The EDTtreated CQD layer as the HTL provides well-optimized energy alignment and a desirable electric field distribution within the active layer. However, it also introduces drawbacks in view of its high density of trap states, [3] strong chemical interaction with the materials in the device stack, [4] and limited stability in encapsulated devices. [5] Importantly, it has a short diffusion length of tens of nm that precludes significant contribution to device photocurrent. [6] An ideal HTL in PbS CQD-SCs should combine appropriate energy levels to allow efficient hole-extraction and electronblocking; [7] sufficient hole mobility for efficient vertical charge transport; [8] a diffusion length enabling contribution to the device photocurrent; [9] materials processing that is compatible with underlying layers in the CQD device; [10] and excellent morphology and conformal coverage to prevent oxygen and moisture permeation. [11] Recently, p-type polymers such as TQ1, P3HT, PDTPBT, and PBDB-TF have been explored as an alternative HTL to replace the EDT-treated CQD layer, but these have failed to render high performance due to unfavorable energy level alignment. [12-15] Benzodithiophene (BDT)-based HTL (PTB7), an alternative to P3HT, has been introduced as a potential HTL in PbS CQD-SCs. The use of PTB7 led to increased PCE due to more suitable energy levels and relatively improved hole-mobility compared to P3HT. Yet, PTB7-based devices still exhibited a limited PCE of 9.6%, [8] significantly lower than of state-of-art CQDs-SC with a PCE of 13.3%, [2] due to low hole mobility of 10 −4 cm 2 V −1 s −1

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“…reported a hydro/oxophobic pore layer for PbS QD solar cells. [ 103 ] The improved optical and electrical properties and stability of the device led to a PCE of 11.7%, and the device retained 90% of its PCE after 1 year ( Figure ).…”

Section: Stability Issue and Design For Qd Pvsmentioning

confidence: 99%

Design Strategy of Quantum Dot Thin‐Film Solar Cells

Kim

Lim

Yun

et al. 2020

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Quantum dots (QDs) are emerging photovoltaic materials that display exclusive characteristics that can be adjusted through modification of their size and surface chemistry. However, designing a QD‐based optoelectronic device requires specialized approaches compared with designing conventional bulk‐based solar cells. In this paper, design considerations for QD thin‐film solar cells are introduced from two different viewpoints: optics and electrics. The confined energy level of QDs contributes to the adjustment of their band alignment, enabling their absorption characteristics to be adapted to a specific device purpose. However, the materials selected for this energy adjustment can increase the light loss induced by interface reflection. Thus, management of the light path is important for optical QD solar cell design, whereas surface modification is a crucial issue for the electrical design of QD solar cells. QD thin‐film solar cell architectures are fabricated as a heterojunction today, and ligand exchange provides suitable doping states and enhanced carrier transfer for the junction. Lastly, the stability issues and methods on QD thin‐film solar cells are surveyed. Through these strategies, a QD solar cell study can provide valuable insights for future‐oriented solar cell technology.

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A hydro/oxo-phobic top hole-selective layer for efficient and stable colloidal quantum dot solar cells

Abstract: In this report, we explore the underlying mechanisms by which doped organic thin films as a top hole-selective layer (HSL) improve the performance and stability of colloidal quantum dot (CQD)-based solar cells.

Cited by 41 publications

References 32 publications

Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

A Tuned Alternating D–A Copolymer Hole‐Transport Layer Enables Colloidal Quantum Dot Solar Cells with Superior Fill Factor and Efficiency

Design Strategy of Quantum Dot Thin‐Film Solar Cells

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