| 1. |
- Tian, Chen, et al.
(författare)
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An effective modulation of bulk perovskite by V2CTx nanosheets for efficient planar perovskite solar cells
- 2023
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:10, s. 5015-5026
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Tidskriftsartikel (refereegranskat)abstract
- Crystallization modulation and defect passivation are key for high performance perovskite solar cells (PSCs) through suppressing defects in the surface and/or near the grain boundaries (GBs) of solution-processed perovskite films. In this work, we report simultaneous modulation of crystallization and passivation of defects for perovskites through a new vanadium carbide (V2CTx) MXene that is employed in an anti-solvent. The final modified perovskite film showed an improved crystallization, better energy level alignment and higher hole injection with a hole-transporting layer, leading to an increased power conversion efficiency from 20.1% up to 23.47% for planar PSCs, with enhanced device stability retaining over 90% of the initial PCE after 1000 hours exposure under 40-60% relative humidity at 25 degrees C. We have further employed the synchrotron radiation in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) equipment to monitor the kinetic process of crystallization during spin-coating; it is notable that a lower dimensional perovskite structure (n < 3) was observed in the modified perovskite film during the process of dropping the antisolvent CB with V2CTx, which helps explain the enhanced device stability.
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| 2. |
- Jeong, Jaeki, et al.
(författare)
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Pseudo-halide anion engineering for α-FAPbI3 perovskite solar cells
- 2021
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 592:7854, s. 381-385
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites of the general formula ABX(3)-where A is a monovalent cation such as caesium, methylammonium or formamidinium; B is divalent lead, tin or germanium; and X is a halide anion-have shown great potential as light harvesters for thin-film photovoltaics(1-5). Among a large number of compositions investigated, the cubic a-phase of formamidinium lead triiodide (FAPbI(3)) hasemerged as the most promising semiconductor for highly efficient and stable perovskite solar cells(6-9), and maximizing the performance of this material in such devices is of vital importance for the perovskite researchcommunity. Here we introduce an anion engineering concept that uses the pseudo-halide anion formate (HCOO-) to suppress anion-vacancy defects that are present at grain boundaries and at the surface of the perovskite films and to augment the crystallinity of the films. Theresulting solar cell devices attain a power conversion efficiency of 25.6 per cent (certified 25.2 per cent), have long-term operational stability (450 hours) and show intense electroluminescence with external quantum efficiencies of more than 10 per cent. Our findings provide a direct route to eliminate the most abundant and deleterious lattice defects present in metal halide perovskites, providing a facile access to solution-processable films with improved optoelectronic performance.
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| 3. |
- Xu, Weidong, et al.
(författare)
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Iodomethane-Mediated Organometal Halide Perovskite with Record Photoluminescence Lifetime
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 8:35, s. 23181-23189
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Tidskriftsartikel (refereegranskat)abstract
- Organometallic lead halide perovskites are excellent light harvesters for high-efficiency photovoltaic devices. However, as the key component in these devices, a perovskite thin film with good morphology and minimal trap states is still difficult to obtain. Herein we show that by incorporating a low boiling point alkyl halide such as iodomethane (CH3I) into the precursor solution, a perovskite (CH3NH3PbI3-xClx) film with improved grain size and orientation can be easily achieved. More importantly, these films exhibit a significantly reduced amount of trap states. Record photoluminescence lifetimes of more than 4 mu s are achieved; these lifetimes are significantly longer than that of pristine CH3NH3PbI3-xClx films. Planar heterojunction solar cells incorporating these CH3I-mediated perovskites have demonstrated a dramatically increased power conversion efficiency compared to the ones using pristine CH3NH3PbI3-xClx. Photoluminescence, transient absorption, and microwave detected photoconductivity measurements all provide consistent evidence that CH3I addition increases the number of excitons generated and their diffusion length, both of which assist efficient carrier transport in the photovoltaic device. The simple incorporation of alkyl halide to enhance perovskite surface passivation introduces an important direction for future progress on high efficiency perovskite optoelectronic devices.
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| 4. |
- Yan, Yajie, et al.
(författare)
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Implementing an intermittent spin-coating strategy to enable bottom-up crystallization in layered halide perovskites
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional halide perovskites (2D PVSKs) have drawn tremendous attentions owing to their outstanding ambient stability. However, the random orientation of layered crystals severely impedes the out-of-plane carrier transport and limits the solar cell performance. An in-depth understanding coupled with an effective control of the crystallization in 2D PVSKs is the crux for highly efficient and durable devices. In this contribution, we accidentally discovered that the crystallization of 2D PVSKs can be effectively regulated by so-called ′intermittent spin-coating (ISC)′ process. Combined analyses of in(ex)-situ grazing-incidence wide-angle X-ray scattering with time-of-flight secondary ion mass spectrometry distinguish the interface initialized bottom-up crystallization upon ISC treatment from the bi-directional one in the conventional spin-coating process, which results in significantly enhanced crystal orientation and thus facilitated carrier transport as confirmed by both electrical measurements and ultrafast spectroscopies. As a result, the p-i-n architecture planar solar cells based on ISC fabricated paradigm PEA2MA3Pb4I13 deliver a respectable efficiency of 11.2% without any treatment, which is three-fold improvement over their spin-coated counterparts and can be further boosted up to 14.0% by NH4Cl addition, demonstrating the compatibility of ISC method with other film optimization strategies.
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| 5. |
- Yu, Shuang, et al.
(författare)
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Imidazole additives in 2D halide perovskites : impacts of -CN versus -CH3 substituents reveal the mediation of crystal growth by phase buffering
- 2022
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 15:8, s. 3321-3330
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Tidskriftsartikel (refereegranskat)abstract
- The unique sandwich structure and favorable crystallization kinetics have endowed two-dimensional (2D) halide perovskites with excellent ambient stability and facile film formation compared to those of their three-dimensional counterparts. However, the heterogeneous crystallization of multiple n-value phases during solution-casting of 2D perovskite thin films results in random and disordered crystalline alignment in conjunction with numerous lattice defects, all of which ultimately impair the device performance. Herein we demonstrate that highly ordered lattice arrangements in 2D lead halide perovskites, exemplified as a paradigm phenylethylamine (PEA) spacer, can be achieved using the 4,5-dicyanoimidazole (DCI) additive without any post-treatment. Electrostatic potential distribution mapping and X-ray photoelectron spectroscopy collectively confirm the Lewis acid-base interaction between -CN− units in DCI and Pb2+, which is conducive to homogeneous nucleation during perovskite crystallization. A sequence of in situ grazing-incident wide-angle X-ray scattering and high-resolution transmission electron microscopy characterization unravel the epitaxial growth of multi-phases that gradually buffer the internal lattice strain and consequently regulate the lattice orientation, which markedly leads to a reduction of trap density and a prolongation of carrier lifetime. The resulting planar solar cells based on 2D PEA2MA3Pb4I13 (n = 4) deliver an outstanding efficiency of ∼17.0% along with excellent operational stability.
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| 6. |
- Yuan, Zhongcheng, et al.
(författare)
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Approximately 800-nm-Thick Pinhole-Free Perovskite Films via Facile Solvent Retarding Process for Efficient Planar Solar Cells
- 2016
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Ingår i: ACS APPLIED MATERIALS and INTERFACES. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 8:50, s. 34446-34454
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Tidskriftsartikel (refereegranskat)abstract
- Device performance of organometal halide perovskite solar cells significantly depends on the quality and thickness of perovskite absorber films. However, conventional deposition methods often generate pinholes within similar to 300 nm-thick perovskite films, which are detrimental to the large area device manufacture. Here we demonstrated a simple solvent retarding process to deposit uniform pinhole free perovskite films with thicknesses up to similar to 800 nm. Solvent evaporation during the retarding process facilitated the components separation in the mixed halide perovskite precursors, and hence the final films exhibited pinhole free morphology and large grain sizes. In addition, the increased precursor concentration after solvent-retarding process led to thick perovskite films. Based on the uniform and thick perovskite films prepared by this convenient process, a champion device efficiency up to 16.8% was achieved. We believe that this simple deposition procedure for high quality perovskite films around micrometer thickness has a great potential in the application of large area perovskite solar cells and other optoelectronic devices.
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| 7. |
- Zou, Yatao, et al.
(författare)
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Boosting Perovskite Light-Emitting Diode Performance via Tailoring Interfacial Contact
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:28, s. 24320-24326
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processed perovskite light-emitting diodes (LEDs) have attracted wide attention in the past several years. However, the overall efficiency and stability of perovskite-based LEDs remain inferior to those of organic or quantum dot LEDs. Nonradiative charge recombination and the unbalanced charge injection are two critical factors that limit the device efficiency and operational stability of perovskite LEDs. Here, we develop a strategy to modify the interface between the hole transport layer and the perovskite emissive layer with an amphiphilic conjugated polymer of poly[(9,9-bis(3-(N,N-dimethylamino)propy1)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN). We show evidences that PFN improves the quality of the perovskite film, which effectively suppresses nonradiative recombination. By further improving the charge injection balance rate, a green perovskite LED with a champion current efficiency of 45.2 cd/A, corresponding to an external quantum efficiency of 14.4%, is achieved. In addition, the device based on the PFN layer exhibits improved operational lifetime. Our work paves a facile way for the development of efficient and stable perovskite LEDs.
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| 8. |
- Zou, Yatao, et al.
(författare)
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Thermal-induced interface degradation in perovskite light-emitting diodes
- 2020
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 8:43, s. 15079-15085
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite light-emitting diodes (PeLEDs) have experienced rapid improvements in device efficiency during the last several years. However, the operational instability of PeLEDs remains a key barrier hindering their practical applications. A fundamental understanding of the degradation mechanism is still lacking but will be important to seek ways to mitigate these unwanted processes. In this work, through comprehensive characterizations of the perovskite emitters and the interfacial contacts, we figure out that Joule heating induced interface degradation is one of the dominant factors affecting the operational stability of PeLEDs. We investigate the interfacial contacts of PeLEDs based on a commonly used device structure, with an organic electron transport layer of 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene (TPBi), and observe obvious photoluminescence quenching of the perovskite layer after device operation. Detailed characterizations of the interlayers and the interfacial contacts reveal that photoluminescence quenching is mainly due to the element inter-diffusion at the interface induced by the morphological evolution of the TPBi layers under Joule heating during the operation of PeLEDs. Our work provides direct insights into the degradation pathways and highlights the importance of exploring intrinsically stable interlayers as well as interfacial contacts beyond the state-of-the-art to further boost the operational stability of PeLEDs.
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