Reducing Defects Density and Enhancing Hole Extraction for Efficient Perovskite Solar Cells Enabled by π-Pb2+ Interactions

Molecular doping is an of significance approach to reduce defects density of perovskite and to improve interfacial charge extraction in perovskite solar cells. Here, we show a new strategy for chemical doping of perovskite via an organic small molecule, which features a fused tricyclic core, showing strong intermolecular π-Pb²⁺ interactions with under-coordinated Pb²⁺ in perovskite. This π-Pb²⁺ interactions could reduce defects density of the perovskite and suppress the nonradiative recombination, which was also confirmed by the density functional theory calculations. In addition, this doping via π-Pb²⁺ interactions could deepen the surface potential and downshift the work function of the doped perovskite film, facilitating the hole extraction to hole transport layer. As a result, the doped device showed high efficiency of 21.41 % with ignorable hysteresis. This strategy of fused tricyclic core-based doping provides a new perspective for the design of new organic materials to improve the device performance.

Carrier Diffusion and Recombination Anisotropy in the MAPbI3 Single Crystal

MAPbI₃, one of the archetypical metal halide perovskites, is an exciting semiconductor for a variety of optoelectronic applications. The photoexcited charge-carrier diffusion and recombination are important metrics in optoelectronic devices. Defects in grain interiors and boundaries of MAPbI₃ films cause significant nonradiative recombination energy losses. Besides defect impact, carrier diffusion and recombination anisotropy introduced by structural and electronic discrepancies related to the crystal orientation are vital topics. Here, large-sized MAPbI₃ single crystals (SCs) were grown, with the (110), (112), (100), and (001) crystal planes simultaneously exposed through the adjusting ratios of PbI₂ to methylammonium iodide (MAI). Such MAPbI₃ SCs exhibit a weak n-type semiconductor character, and the Fermi levels of these planes were slightly different, causing a homophylic p-n junction at crystal ledges. Utilizing MAPbI₃ SCs, the photoexcited carrier diffusion and recombination within the crystal planes and around the crystal ledges were investigated through time-resolved fluorescence microscope. It is revealed that both the (110) and (001) planes were facilitated to be exposed with more MAI in the growth solutions, and the photoluminescence (PL) of these planes manifesting a red-shift, longer carrier lifetime, and diffusion length compared with the (100) and (112) planes. A longer carrier diffusion length promoted photorecycling. However, excessive MAI-assisted grown MAPbI₃ SCs could increase the radiative recombination. In addition, it revealed that the carrier excited within the (001) and (112) planes was inclined to diffuse toward each other and was favorable to be extracted out of the grain boundaries or crystal ledges.

Evaluation of the Haemophilus influenzae EUCAST and CLSI disc diffusion methods to recognize aminopenicillin and amoxicillin/clavulanate resistance

OBJECTIVES

Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of β-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis.

METHODS

A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with β-lactam resistance, other than that due to isolated β-lactamase production.

RESULTS

Of the 100 isolates, 32 were categorized as either β-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or β-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates.

CONCLUSIONS

The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required.

Dual-Functional Additive to Simultaneously Modify the Interface and Grain Boundary for Highly Efficient and Hysteresis-Free Perovskite Solar Cells

The efficiency loss and stability issues of perovskite devices mainly derive from nonradiative recombination, caused by detrimental defects in the perovskite bulk and at the interface between the perovskite absorber and charge transport layer. Therefore, the passivation of these defects is of great concern in achieving high-performance perovskite devices. Here, we report the incorporation of potassium phenyl trifluoroborate (KC₆H₅BF₃) into perovskite films to realize simultaneous passivation of the grain boundaries and the perovskite/SnO₂ interface. Apart from the bulk passivation of K⁺, the accumulation of C₆H₅BF₃^- at the buried interface contributes to the compact contact between the perovskite absorber and SnO₂ layer and also the perfect columnar perovskite grains. As a result, the KC₆H₅BF₃-containing perovskite films exhibit low trap density. The distinct enhancements of open-circuit voltage and photoelectric conversion efficiency are obtained together with negligible hysteresis. The open-circuit voltage of the KC₆H₅BF₃-containing device increases from 1.09 to 1.18 V, and the corresponding efficiency increases from 19.69 to 22.33%. The finding in this work shows the superiority of the dual-functional additive for preparing highly efficient perovskite devices.

High-Pressure Nitrogen-Extraction and Effective Passivation to Attain Highest Large-Area Perovskite Solar Module Efficiency

Slot-die coating holds advantages over other large-scale technologies thanks to its potential for well-controlled, high-throughput, continuous roll-to-roll fabrication. Unfortunately, it is challenging to control thin.film uniformity over a large area while maintaining crystallization quality. Herein, by using a high-pressure nitrogen-extraction (HPNE) strategy to assist crystallization, a wide processing window in the well-controlled printing process for preparing high-quality perovskites is achieved. The yellow-phase perovskite generated by the HPNE acts as a crucial intermediate phase to produce large-area high-quality perovskite film. Furthermore, an ionic liquid is developed to passivate the perovskite surface to reduce surface defect density and to suppress carrier recombination, resulting in significantly increased efficiency to 22.7%, the highest for large-area fabrication. The strategies are successfully extended to large-area device fabrication, making it possible to produce a 40 × 40 mm² module with stabilized PCE as high as 19.4%, the highest-efficiency for a large-area module to date.

The Possible Side Reaction in the Annealing Process of Perovskite Layers

The high purity of light harvesting layers is one of the core issues for highly efficient perovskite solar cells. The perovskite precursor solution and the crystallization growth of thin films have been extensively studied in the past few years. Herein, we have unveiled some side reactions that occur during the evaporation of the residual solvent in the spin-coated films at elevated temperature, forming N-methyl formamidium iodide and N,N'-dimethyl formamidium iodide. Such side reactions will consume the precursor materials and then produce a secondary phase in the perovskite films, which is detrimental for the performance improvement. We have also found that a combination of room temperature aging and vacuum treatment of the spin-coated wet film is conducive to eliminate the side reactions and improve the perovskite phase purity, reaching an efficiency of 20.98%.

Cs4 PbI6 -Mediated Synthesis of Thermodynamically Stable FA0.15 Cs0.85 PbI3 Perovskite Solar Cells

The stability issue is still one of the main limitations of the commercialization of perovskite photovoltaics. The mixed cation FA_x Cs_{1 -x} PbI₃ has shown great promise owing to its improved thermal and moisture stability. However, the study of FA_x Cs_{1 -x} PbI₃ is concentrated on formamidine (FA)-rich perovskite, whereas cesium (Cs)-rich FA_x Cs_{1 -x} PbI₃ perovskites are barely studied due to the inevitable phase separation when Cs > 30 mol%. Here, a Cs₄ PbI₆ -mediated method is developed to synthesize Cs-rich FA_x Cs_{1 -x} PbI₃ perovskites. It is demonstrated that Cs₄ PbI₆ intermediate phase has a low Cs cation diffusion barrier and therefore offers a fast ion exchange with the preformed FA-rich perovskite phase to finally form the Cs-rich FA_x Cs_{1 -x} PbI₃ perovskite. The results indicate that ≈15% alloying with organic FA cations can sufficiently stabilize the perovskite phase with excellent phase and UV-irradiation stability. The FA_0.15 Cs_0.85 PbI₃ perovskite solar cells achieve a champion power conversion efficiency of 17.5%, showing the great potential of Cs-based perovskites for efficient and stable solar cells.

Comparison of single and dual latent tuberculosis screening strategies before biologic and targeted therapy in patients with rheumatic diseases: a retrospective cohort study

PURPOSE

Before biologic and targeted synthetic disease-modifying antirheumatic drug (b/tsDMARD) treatment, latent tuberculosis infection (LTBI) screening by tuberculin skin test (TST) or interferon gamma release assay (IGRA) is recommended. However, both tests have reduced reliability in immunosuppressed patients. We investigated whether dual LTBI screening with both tests could reduce the incidence of tuberculosis.

METHODS

Consecutive patients receiving b/tsDMARDs for rheumatic diseases in a regional hospital were recruited. All patients underwent either TST/IGRA or both. They were categorised into a single or dual testing group and were followed up for at least 6 months. Isoniazid was prescribed if any one test was positive.

RESULTS

In total, 217 patients were included in this study; 121 underwent single LTBI testing and 96 underwent dual testing. Tuberculosis occurred in nine patients in the single testing group and one patient in the dual testing group (7.4% vs 1.0%, P=0.045). However, the difference was not statistically significant when follow-up duration was considered (log rank test). In total, 71 patients tested positive for LTBI with isoniazid treatment (28.9% in the single testing group and 45.8% in the dual testing group, P=0.007). Agreement between the IGRA and TST was 74.4% (Cohen's kappa=0.413); agreement was lower in patients receiving prednisolone. Infliximab use was independently associated with tuberculosis (P=0.032). Mild isoniazid-related side-effects occurred in seven patients.

CONCLUSIONS

Dual LTBI testing with both TST and IGRA is effective and safe. It might be useful for patients receiving prednisolone at the time of LTBI screening, or if infliximab therapy is anticipated.

Influence of protogynous sex change on recovery of fish populations within marine protected areas

Marine protected areas (MPAs) are increasingly implemented as a conservation tool worldwide. In many cases, they are managed adaptively: the abundance of target species is monitored, and observations are compared to some model-based expectation for the trajectory of population recovery to ensure that the MPA is achieving its goals. Most previous analyses of the transient (short-term) response of populations to the cessation of fishing inside MPAs have dealt only with gonochore (fixed-sex) species. However, many important fishery species are protogynous hermaphrodites (female-to-male sex-changing). Because size-selective harvest will predominantly target males in these species, harvesting not only reduces abundance but also skews the sex ratio toward females. Thus the response to MPA implementation will involve changes in both survival and sex ratio, and ultimately reproductive output. We used an age-structured model of a generic sex-changing fish population to compare transient population dynamics after MPA implementation to those of an otherwise similar gonochore population and examine how different features of sex-changing life history affect those dynamics. We examined both demographically open (most larval recruitment comes from outside the MPA) and demographically closed (most larval recruitment is locally produced) dynamics. Under both scenarios, population recovery of protogynous species takes longer when fishing was more intense pre-MPA (as in gonochores), but also depends heavily on the mating function, the degree to which the sex ratio affects reproduction. If few males are needed and reproduction is not affected by a highly female-biased sex ratio, then population recovery is much faster; if males are a limiting resource, then increases in abundance after MPA implementation are much slower than for gonochores. Unfortunately, the mating function is largely unknown for fishes. In general, we expect that most protogynous species with haremic mating systems will be in the first category (few males needed), though there is at least one example of a fish species (though not a sex-changing species) for which males are limiting. Thus a better understanding of the importance of male fish to population dynamics is needed for the adaptive management of MPAs.

UV degradation of the interface between perovskites and the electron transport layer

The stability of the perovskite/electron transport layer (ETL) interface is critical for perovskite solar cells due to the presence of ultraviolet (UV) light in the solar spectrum. Herein, we have studied the decomposition process and performance evolution of the perovskite layer in contact with different ETLs under strong ultraviolet irradiation. The normally used SnO₂ layer has lower photocatalytic activity in comparison with the TiO₂ layer, but the perovskite/SnO₂ interface is still severely decomposed along with the formation of hole structures. Such UV light-induced decomposition, on the one hand, leads to the decomposition of the perovskite phase into PbI₂ and more seriously, the formed hole structure significantly limits the carrier injection at the interface owing to the separation of the perovskite active layer from ETLs. Under the same conditions, the perovskite/PCBM interface is very stable and maintains a highly efficient carrier injection. There is no significant efficiency degradation of the encapsulated PCBM-based devices measured outdoors for about three months.

Using SnO₂ as the ETL in perovskite solar cells can degrade the interface and cause device performance degradation under UV light.

Photo-Supercapacitors Based on Third-Generation Solar Cells

Photopowered energy systems (PPESs), which simultaneously achieve power conversion and energy storage, are one of the most promising auxiliaries to fulfill the giant and diversified power demand in modern society. Devices with a low cost, wearable, compact structure and the potential to add a variety of features (such as photochromic, flexible, textile, and wearable) have received extensive research attention. Photo-supercapacitors are becoming one of the most extensively researched PPESs due to their ease of fabrication, mitigation of solar irradiation discontinuities, and the promotion of renewable energy utilization, and these devices have been fabricated with different combinations of photovoltage devices and energy-storage technologies. This review summarizes the development of photo-supercapacitors that integrate third-generation solar cells and supercapacitors, with a focus on materials alignment, performance, structure design, and application. Finally, current challenges, possible solutions, and future perspectives are discussed.