The voltage (V) and light-power (P) dependences of electrochemical impedance spectroscopy (EIS) curves of perovskite solar cells (PSCs) are investigated over the entire (V, P) space rather than ...limited to short-circuit or open-circuit conditions. For the first time, we report that under fixed V and increasing P, the EIS curves show complicated behaviors. Employing a modified Randles circuit, we successfully fitted the data using three newly proposed empirical equations. From the behaviors of the fitting parameters in the (V, P) space, we conclude that the dynamics inside PSCs consists of two parts: (1) the migration of mobile ions/vacancies and their capturing of the free carriers at the perovskite layer boundary and (2) a classical diode involving the migration and recombination of free carriers. Our calculated diffusivity and mobility agree with those of previous reports. We further found that the mobile ion density inside the perovskite layer is proportional to light power, which could explain the inverse linear power dependence of the amplitude of the slower EIS feature and the resonance time and amplitude of the faster one.
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IJS, KILJ, NUK, PNG, UL, UM
This study investigated whether Korean children follow the acquisition pattern predicted by the Aspect Hypothesis (Shirai & Andersen, 1995), and the relationship between caretakers' and children's ...speech. Accordingly, we analyzed a Korean corpus (Ryu-Corpus) on the CHILDES database (MacWhinney, 2000), which comprised longitudinal video-recorded interactions of three Korean children and their caregivers. Results indicate that the children used the past marker -ess principally with telic verbs, consistent with the Aspect Hypothesis. Each child's usage closely reflects the caretaker's frequency, yielding a high correlation (τb = 0.79). However, the acquisition of the imperfective marker -ko iss did not show a predicted association with activity verbs, contrary to the Aspect Hypothesis. Furthermore, caretakers' input did not correlate with the children's utterances of the imperfective marker (τb = 0.40). We argue that multiple factors such as input frequency, language-specific organization of aspectual semantics, and individual differences should be considered to explain tense-aspect acquisition.
Impedance spectroscopy has been widely used in characterizing the electronic properties of semiconductors. Its application in the perovskite photovoltaic research is a natural extension of the ...well‐established methodology in the new semiconducting material. However, it turns out that the published results are sometimes very strange, difficult to interpret, or the interpretations contradict each other. It is now clear that most of these troubles stem from the dominating influence of ionic contributions. Herein, some of the published data are reviewed and the possible problems are identified, which can be reconciled by taking into account the explicit contribution of the ionic behavior.
Temperature dependent Nyquist plots of a perovskite device under a weak light (0.1 mW cm−2) illumination exhibit drastically different behavior compared with an ordinary inorganic photodiode, because of the influence of the ionic motion over the electronic current.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A high‐quality mixed‐organic‐cation perovskite (MA)x(FA)1−xPbI3 is prepared from a phase‐pure non‐stoichiometric intermediate complex (FAI)1−x−PbI2. The phase‐pure (FAI)1−x−PbI2 probably facilitates ...homogenous nucleation and modulates the growth kinetics during the crystallization of (MA)x(FA)1−xPbI3. This strategy can be expected to pave the way for the development of mixed‐organic‐cation perovskite solar cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Wide-band-gap (WB) perovskite devices are promising as the top cell of silicon-perovskite tandem devices to boost the efficiency beyond the Shockley–Queisser limit. Here, we tailor the performance ...parameters of WB mixed-halide perovskite solar cell with long alkyl chain-substituted fullerene derivatives as an electron transport layer (ETL). The device with C60-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12) demonstrates an enhanced power conversion efficiency of 16.74% with the record open circuit voltage (V OC) of 1.24 V, an increase by 70 mV with concomitant V OC deficit reduction to 0.47 V. This is achieved by mitigating the recombination loss through the use of highly crystalline C60MC12 film compared to amorphous 6,6-phenyl-C61-butyric acid methyl ester layer. The device analysis reveals the soothing of the defect activities with shallower defect states and passivation of the interface recombination centers for the device with C60MC12. We ascribe this property to the crystallinity of fullerene derivatives as ETL, which is also important for the optimization of device parameters, besides the band alignment matching of WB perovskite devices.
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IJS, KILJ, NUK, PNG, UL, UM
In
this study, highly stable, low-temperature-processed planar
lead halide perovskite (MAPbI
3–
x
Cl
x
) solar cells with NiO
x
interfaces have been developed. Our solar cells
maintain over 85% of ...the initial efficiency for more than 670 h, at
the maximum power point tracking (MPPT) under 1 sun illumination (no
UV-light filtering) at 30 °C, and over 73% of the initial efficiency
for more than 1000 h, at the accelerating aging test (85 °C)
under the same MPPT condition. Storing the encapsulated devices at
85 °C in dark over 1000 h revealed no performance degradation.
The key factor for the prolonged lifetime of the devices was the sputter-deposited
polycrystalline NiO
x
hole transport layer
(HTL). We observed that the properties of NiO
x
are dependent on its composition. At a higher Ni
3+
/Ni
2+
ratio, the conductivity of NiO
x
is higher, but at the expense of optical transmittance. We obtained
the highest power conversion efficiency of 15.2% at the optimized
NiO
x
condition. The sputtered NiO
x
films were used to fabricate solar cells without
annealing or any other treatments. The device stability enhanced significantly
compared to that of the devices with PEDOT:PSS HTL. We clearly demonstrated
that the illumination-induced degradation depends heavily on the nature
of the HTL in the inverted perovskite solar cells (PVSCs). The sputtered
NiO
x
HTL can be a good candidate to solve
stability problems in the lead halide PVSCs.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
Background:Atrial fibrillation (AF) is a common cardiac arrhythmia, associated with increased cardiovascular morbidity and mortality including thromboembolic events. The aims of this study were to ...assess the prevalence of left atrial appendage (LAA) thrombi in Japanese non-valvular atrial fibrillation (NVAF) patients undergoing preprocedural transesophageal echocardiography (TEE) during anticoagulation therapy, and to compare the efficacy of warfarin and direct oral anticoagulants (DOAC).Methods and Results:This retrospective study reviewed records of 559 consecutive NVAF patients (445 men; age, 62±11 years) undergoing preprocedural TEE following at least 3 weeks of anticoagulation therapy. Of these, 275 patients had non-paroxysmal AF (49%). LAA thrombus was observed in 15 patients (2.7%). The prevalence of LAA thrombi was similar between the DOAC group (2.6%) and the warfarin group (2.8%, P=0.86). No patients with CHA2DS2-VASc score=0, or paroxysmal AF without prior stroke or transient ischemic attack, had LAA thrombi. On univariate analysis, non-paroxysmal AF, structural heart disease, antiplatelet therapy, larger left atrium, higher brain natriuretic peptide (BNP), reduced LAA flow, and higher CHA2DS2-VASc score were all associated with LAA thrombi. On multivariate analysis, BNP ≥173 pg/mL remained the only independent predictor of LAA thrombi.Conclusions:LAA thrombi were found in 2.7% of Japanese NVAF patients scheduled for procedures despite ongoing oral anticoagulation therapy. Incidence of thrombi was similar for patients on DOAC and on warfarin.
The carrier transport layers (CTLs) have exhibited the influence on performance and stability of halide perovskite solar cells (HaPSCs). The exploration of characteristic impacts on HaPSCs induced by ...the CTL unveils the key factors underlying the device physics. In this work, we investigate the impacts of the organic or inorganic hole transport layer (HTL) in HaPSCs by analyzing the elemental distribution, the current–voltage characteristics, and the capacitance spectroscopy. The organic HTL device shows the lower activation energy (E A < E g) indicating a dominant interface-mediated recombination. The defect analysis reveals that the device with the inorganic HTL induces rather deep antisite defects with slightly higher trap densities. This is attributed to the diffusion of metal cations into the halide perovskite (HaP) during crystallization of HaP layer grown on the inorganic HTLs. Our results suggest that the passivation of deep defect and suppression of trap densities in the HaP either using ideal CTLs or optimizing the fabrication route is crucial to improving the device parameters approaching the theoretical limit.
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IJS, KILJ, NUK, PNG, UL, UM
Bismuth-based halide perovskites (Bi-HaP) are low toxicity and air-stable materials with promising photo-absorber properties. In this study, we fabricated Bi-HaP (Cs
3
Bi
2
I
9
and CsBi
3
I
10
) ...films by a solution process followed by solvent annealing and investigated the crystal growth and optoelectronic properties of these materials. A compact and large grain morphology of the Bi-HaP films was realized by annealing under ambient solvent vapor conditions. Collective analysis of XRD patterns, and Raman spectra, absorption and PL spectra of the fabricated films corroborates that the Cs
3
Bi
2
I
9
film (
E
g
∼ 2.08 eV) with a hexagonal crystal phase is more stable under annealing conditions in a wide temperature range and ambient solvent vapor annealing conditions as compared to the other CsBi
3
I
10
thin film, having the narrower
E
g
∼ 1.8 eV, of the Bi-HaP family. We have achieved the best power conversion efficiency as high as ∼1.26% with the open circuit voltage of 0.74 V for the device fabricated with Cs
3
Bi
2
I
9
. The analysis of material properties and device characteristics indicates that morphology tailoring, surface chemistry control, and interface band offset engineering are important for the further improvement of Bi-HaP-based devices.
Antisolvent treatment followed by solvent vapor annealing affected the morphology of the caesium bismuth halide film and impacted the device parameter tuning by the carrier transport layer.
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