| 1. |
- Beal, Jacob, et al.
(författare)
-
Robust estimation of bacterial cell count from optical density
- 2020
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
|
|
| 2. |
- Yan, Yajie, et al.
(författare)
-
Implementing an intermittent spin-coating strategy to enable bottom-up crystallization in layered halide perovskites
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
-
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.
|
|
| 3. |
- Ba, Kun, et al.
(författare)
-
Billiard Catalysis at Ti3C2 MXene/MAX Heterostructure for Efficient Nitrogen Fixation
- 2022
-
Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 317, s. 121755-
-
Tidskriftsartikel (refereegranskat)abstract
- Electrocatalytic ammonia (NH3) conversion under ambient atmosphere is crucial to mimic the nature's nitrogen cycle. But currently it is always interrupted by the HER process which is more competitive. Herein, we tactically cultivate a series of incompletely etched Ti3AlC2 MAX / Ti3C2 MXene based heterostructure catalysts whose composition can be finely tuned through regulation of the LiF percentage in mixed chemical etching agent. Notably, the surface potential difference between MAX and MXene is ~40 mV, indicating that the electron can be readily transferred from MAX to MXene across the interfaces, which is favorable for N2 fixation, yielding an outstanding Faradic efficiency of 36.9%. Furthermore, density functional theory calculations reveal the billiard-like catalysis mechanism, where the intermediates are alternatively adsorbed on MAX or MXene surfaces. Meanwhile, the rate-determining step of *NH → *NH2 possesses an energy barrier of 0.96 eV on the hetero-interface which follows associative distal mechanism. This work opens a new frontier of heterostructured catalyst for balancing electrical conductivity and catalytic activity in electrocatalysis.
|
|
| 4. |
- Chen, Yani, et al.
(författare)
-
2D Ruddlesden-Popper Perovskites for Optoelectronics
- 2018
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648. ; 30:2, s. 1703487-1703487
-
Tidskriftsartikel (refereegranskat)abstract
- Conventional 3D organic-inorganic halide perovskites have recently undergone unprecedented rapid development. Yet, their inherent instabilities over moisture, light, and heat remain a crucial challenge prior to the realization of commercialization. By contrast, the emerging 2D Ruddlesden-Popper-type perovskites have recently attracted increasing attention owing to their great environmental stability. However, the research of 2D perovskites is just in their infancy. In comparison to 3D analogues, they are natural quantum wells with a much larger exciton binding energy. Moreover, their inner structural, dielectric, optical, and excitonic properties remain to be largely explored, limiting further applications. This review begins with an introduction to 2D perovskites, along with a detailed comparison to 3D counterparts. Then, a discussion of the organic spacer cation engineering of 2D perovskites is presented. Next, quasi-2D perovskites that fall between 3D and 2D perovskites are reviewed and compared. The unique excitonic properties, electron-phonon coupling, and polarons of 2D perovskites are then be revealed. A range of their (opto)electronic applications is highlighted in each section. Finally, a summary is given, and the strategies toward structural design, growth control, and photophysics studies of 2D perovskites for high-performance electronic devices are rationalized.
|
|
| 5. |
- Chen, Yani, et al.
(författare)
-
Composition Engineering in Two-Dimensional Pb-Sn-Alloyed Perovskites for Efficient and Stable Solar Cells
- 2018
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:25, s. 21343-21348
-
Tidskriftsartikel (refereegranskat)abstract
- Environmentally friendly tin (Sn)-based metallic halide perovskites suffer from oxidation and morphological issues. Here, we demonstrate the composition engineering of Pb-Sn-alloyed two-dimensional (2D) Ruddlesden-Popper perovskites, (BA)2(MA)3Pb4-xSnxI13, for efficient and stable solar cell applications. Smooth thin films with high surface coverage are readily formed without using any additive owing to the self-assembly characteristic of 2D perovskites. It is found that Sn plays a significant role in improving the crystallization and crystal orientation while narrowing the bandgap of Pb-Sn 2D perovskites. Photophysical studies further reveal that the optimal Sn ratio (25 mol %) based sample exhibits both minimized trap density and weakened quantum confinement for efficient charge separation. Consequently, the optimized (BA)2(MA)3Pb3SnI13-based solar cells yield the best power conversion efficiency close to 6% with suppressed hysteresis.
|
|
| 6. |
- Chen, Yani, et al.
(författare)
-
Tailoring Organic Cation of 2D Air-Stable Organometal Halide Perovskites for Highly Efficient Planar Solar Cells
- 2017
-
Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832. ; 7:18
-
Tidskriftsartikel (refereegranskat)abstract
- 2D perovskites have recently been shown to exhibit significantly improved environmental stability. Derived from their 3D analogues, 2D perovskites are formed by inserting bulky alkylammonium cations in-between the anionic layers. However, these insulating organic spacer cations also hinder charge transport. Herein, such a 2D perovskite, (iso-BA)2(MA)3Pb4I13, that contains short branched-chain spacer cations (iso-BA+) and shows a remarkable increase of optical absorption and crystallinity in comparison to the conventional linear one, n-BA+, is designed. After applying the hot-casting (HC) technique, all these properties are further improved. The HC (iso-BA)2(MA)3Pb4I13 sample exhibits the best ambient stability by maintaining its initial optical absorption after storage of 840 h in an environmental chamber at 20 °C with a relative humidity of 60% without encapsulation. More importantly, the out-of-plane crystal orientation of (iso-BA)2(MA)3Pb4I13 film is notably enhanced, which increases cross-plane charge mobility. As a result, the highest power conversion efficiencies (PCEs) measured from for current density versus voltage curves afford 8.82% and 10.63% for room-temperature and HC-processed 2D perovskites based planar solar cells, respectively. However, the corresponding steady-state PCEs are remarkably lower, which is presumably due to the significant hysteresis phenomena caused by low charge extraction efficiency at interfaces of C60/2D perovskites.
|
|
| 7. |
- Ji, Jingjing, et al.
(författare)
-
Developing Halogen-Free Polymer Donors for Efficient Nonfullerene Organic Solar Cells by Addition of Highly Electron-Deficient Diketopyrrolopyrrole Unit
- 2021
-
Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 5:5
-
Tidskriftsartikel (refereegranskat)abstract
- High-performance polymer donors when paired with nonfullerene acceptors are mainly limited to flanking halogenated benzodithiophene (BDT)-based π-conjugated copolymers, which however involve complex synthetic procedures. Herein, a series of halogen-free polymer donors that link BDT moiety with two highly electron-deficient benzodithiophene-dione (BDD) and diketopyrrolopyrrole (DPP) units with various molar ratios is developed. Compared with the benchmark PBDB-T donor containing BDD unit, additional incorporation of a stronger electron-negative DPP unit markedly lowers frontier molecular orbital levels and extends optical absorption, potentially leading to simultaneously enhanced VOC and JSC in organic solar cells. A remarkable power conversion efficiency (PCE) of 10.28% is thus obtained in the optimal P75 (BDD : DPP = 3:1 mol%) and Y6 blend cells in comparison with the reference PBDB-T:Y6 (9.20%). A slight addition of PC71BM into the blend is found to further generate finer phase-separated domains and thus increase the best efficiency up to 12.20%. The subtly critical roles of PC71BM are determined by transient absorption measurements on both thin-film and in situ devices to be the prolonged free charge carrier lifetime and the shallow charge transfer states, which enhance JSC and fill factor in the device, respectively.
|
|
| 8. |
- Liu, Xiaoyu, et al.
(författare)
-
Unveiling Excitonic Dynamics in High-Efficiency Nonfullerene Organic Solar Cells to Direct Morphological Optimization for Suppressing Charge Recombination
- 2019
-
Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 6:8
-
Tidskriftsartikel (refereegranskat)abstract
- Nonfullerene acceptors (NFAs)-based organic solar cells (OSCs) have recently drawn considerable research interests; however, their excitonic dynamics seems quite different than that of fullerene acceptors-based devices and remains to be largely explored. A random terpolymer of PBBF11 to pair with a paradigm NFA of 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC) such that both complementary optical absorption and very small offsets of both highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels are acquired is designed and synthesized. Despite the small energy offsets, efficient electron/hole transfer between PBBF11 and ITIC is both clearly observed from steady-state photoluminescence and transient absorption spectra and also supported by the measured low exciton binding energy in ITIC. Consequently, the PBBF11:ITIC-based OSCs afford an encouraging power conversion efficiency (PCE) of 10.02%. Although the good miscibility of PBBF11 and ITIC induces a homogenous blend film morphology, it causes severe charge recombination. The fullerene acceptor of PC 71 BM with varying loading ratios is therefore added to modulate film morphology to effectively reduce the charge recombination. As a result, the optimal OSCs based on PBBF11:ITIC:PC 71 BM yield a better PCE of 11.4% without any additive or annealing treatment.
|
|
| 9. |
- Peng, Jiajun, et al.
(författare)
-
Insights into charge carrier dynamics in organo-metal halide perovskites : From neat films to solar cells
- 2017
-
Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 46:19, s. 5714-5729
-
Forskningsöversikt (refereegranskat)abstract
- Organo-metal halide perovskites have recently obtained world-wide attention as promising solar cell materials. They have broad and strong light absorption along with excellent carrier transport properties which partially explain their record power conversion efficiencies above 22%. However, the basic understanding of the underlying physical mechanisms is still limited and there remain large discrepancies among reported transport characteristics of perovskite materials. Notably, the carrier mobility of perovskite samples either in thin films or within solar cells obtained using different techniques can vary by up to 7-8 orders of magnitude. This tutorial review aims to offer insights into the scope, advantages, limitations and latest developments of the techniques that have been applied for studying charge carrier dynamics in perovskites. We summarize a comprehensive set of measurements including (1) time-resolved laser spectroscopies (transient absorption, time-resolved photoluminescence, terahertz spectroscopy and microwave conductivity); (2) electrical transient techniques (charge extraction by linearly increasing voltage and time-of-flight); and (3) steady-state methods (field-effect transistor, Hall effect and space charge limited current). Firstly, the basics of the above measurements are described. We then comparatively summarize the charge carrier characteristics of perovskite-based neat films, bilayer films and solar cells. Finally, we compare the different approaches in evaluating the key parameters of transport dynamics and unravel the reasons for the large discrepancies among these methods. We anticipate that this tutorial review will serve as the entry point for understanding the experimental results from the above techniques and provide insights into charge carrier dynamics in perovskite materials and devices.
|
|
| 10. |
- Tian, Chen, et al.
(författare)
-
An effective modulation of bulk perovskite by V2CTx nanosheets for efficient planar perovskite solar cells
- 2023
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:10, s. 5015-5026
-
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.
|
|
