Low-loss contacts on textured substrates for inverted perovskite solar cells.

Inverted perovskite solar cells (PSCs) promise enhanced operating stability compared to their normal-structure counterparts1-3. To improve efficiency further, it is crucial to combine effective light management with low interfacial losses4,5. Here we develop a conformal self-assembled monolayer (SAM) as the hole-selective contact on light-managing textured substrates. Molecular dynamics simulations indicate that cluster formation during phosphonic acid adsorption leads to incomplete SAM coverage. We devise a co-adsorbent strategy that disassembles high-order clusters, thus homogenizing the distribution of phosphonic acid molecules, and thereby minimizing interfacial recombination and improving electronic structures. We report a laboratory-measured power conversion efficiency (PCE) of 25.3% and a certified quasi-steady-state PCE of 24.8% for inverted PSCs, with a photocurrent approaching 95% of the Shockley-Queisser maximum. An encapsulated device having a PCE of 24.6% at room temperature retains 95% of its peak performance when stressed at 65 °C and 50% relative humidity following more than 1,000 h of maximum power point tracking under 1 sun illumination. This represents one of the most stable PSCs subjected to accelerated ageing: achieved with a PCE surpassing 24%. The engineering of phosphonic acid adsorption on textured substrates offers a promising avenue for efficient and stable PSCs. It is also anticipated to benefit other optoelectronic devices that require light management.

Breaking the bottleneck of lead-free perovskite solar cells through dimensionality modulation.

The emerging perovskite solar cell (PSC) technology has attracted significant attention due to its superior power conversion efficiency (PCE) among the thin-film photovoltaic technologies. However, the toxicity of lead and poor stability of lead halide materials hinder their commercialization. In this case, after a decade of effort, various categories of lead-free perovskites and perovskite-like materials have been developed, including tin halide perovskites, double perovskites, defect-structured perovskites, and rudorffites. However, the performance of the corresponding devices still falls short of expectations, especially their PCE. The limitations mainly originate from either the unstable lattice structure of these materials, which causes the distortion of their octahedra, or their low dimensionality (e.g., structural and electronic dimensionality)-correlated poor carrier transport and self-trapping effect, accelerating nonradiative recombination. Therefore, understanding the relationship between the structures and performance in these emerging candidates and leveraging these insights to design or modify new lead-free perovskites is of great significance. Herein, we review the variety of dimensionalities in different categories of lead-free perovskites and perovskite-like materials and conclude that dimensionality is an important aspect among the crucial indexes that determine the performance of lead-free PSCs. In addition, we summarize the modulation of both structural and electronic dimensionality, and the corresponding enhanced optoelectronic properties in different categories. Finally, perspectives on the future development of lead-free perovskites and perovskite-like materials for photovoltaic applications are provided. We hope that this review will provide researchers with a concise overview of these emerging materials and help them leverage dimensionality to break the bottleneck in photovoltaic applications.

Cytokine profiles and virological markers highlight distinctive immune statuses, and effectivenesses and limitations of NAs across different courses of chronic HBV infection.

PURPOSE: The characteristics of cytokine/chemokine(CK) profiles across different courses of chronic hepatitis B virus infection and the effects of NAs antiviral therapy on cytokine profiles remain unclear. METHODS: This report provides evidence from 383 patients with chronic HBV infection. The Luminex multiple cytokine detection technology was used to detect CK profiles. The predictive power of CKs across course of disease was assessedusing univariate analyses and with receiver operating characteristic (ROC) curves. RESULTS: Compared to healthy control (HC), expression levels of interleukin 6 (IL)-6, IL-8, IL-21, matrix metalloproteinases (MMP)-2 and tumor necrosis factor receptor (TNFR)-1 showed a significant increasing trend during chronic HBV infection. IL-23 and IL-33 increased respectively in chronic hepatitis B patients (CHB). interferon (IFN)-gamma and TNF-α changed significantly only in liver cirrhosis (LC) patients. Whereas, myeloid-related markers decreased dramatically in those with hepatocellular carcinoma (HCC). The ROC result suggests that combining IL-6, IL-8, CXCL9 and CXCL13 into a nomogram has closely correlation with HCC during chronic HBV infection. In addition, nucleotide analogues (NAs) antiviral treatments are capable of recoveringnormal liver functions and significantly reducing the viral loads, however, they seem to have a limited effect in changing CKs, especially specific antiviral factors. CONCLUSION: The differential CK and virological markers may serve as potential indicators of distinct immune statuses in chronic HBV infection. They also underscore the varying efficacy and limitations of NAs antiviral therapies. This next step would to break new ground in the optimization of current anti-HBV treatment programs although this requires further research.

Controlled Core/Crown Growth Enables Blue-Emitting Colloidal Nanoplatelets with Efficient and Pure Photoluminescence.

Colloidal semiconductor CdSe nanoplatelets (NPLs) feature ultranarrow and anisotropic emissions. However, the optical performance of blue-emitting NPLs is deteriorated by trap states, currently exhibiting tainted emissions and inferior photoluminescence quantum yields (PLQYs). Here, near trap-free blue-emitting NPLs are achieved by the controlled growth of the core/crown. Deep trap states in NPLs can be partially suppressed with the asymmetrical crown growth and are further suppressed with the growth of the small core and the alloyed symmetrical crown, yielding NPLs with pure blue emissions and near-unity PLQYs. Exciton dynamic research based on these NPLs indicates that the trap emission stems from surface traps. Besides, light-emitting diodes exhibiting ultranarrow emission centered around 461 nm with full-width-at-half-maximums down to 11 nm are fabricated using these NPLs.

Spontaneous Formation of Lead-Free Cs3 Cu2 I5 Quantum Dots in Metal-Organic-Frameworks with Deep-Blue Emission.

All-inorganic lead-free Cs3 Cu2 I5  perovskite-derivant quantum dots (QDs) have attracted tremendous attention due to their nontoxicity and unique optoelectronic properties. However, the traditional hot-injection method requires high temperatures and multiple ligands to confine the growth of QDs. Herein, a strategy is reported to spontaneously synthesize ultrasmall Cs3 Cu2 I5  QDs within metal-organic-frameworks (MOFs) MOF-74 at room temperature (RT) with an average diameter of 4.33 nm. The obtained Cs3 Cu2 I5  QDs exhibit an evident deep-blue emission with Commission Internationale de L'Eclairage coordinates of (0.17, 0.07), owing to the strong quantum confinement effect. Due to the protection of MOF-74, the Cs3 Cu2 I5  QDs demonstrate superior stability, and the photoluminescence quantum yield retains 89% of the initial value after the storage of 1440 h under the environment with relative humidity exceeding 70%. Besides, triplet-triplet annihilation upconversion emission is observed within the composite of Cs3 Cu2 I5 @MOF-74, which brings out apparent temperature-dependent photoluminescence. This study reveals a facile method for fabricating ultrasmall lead-free perovskite-derivant QDs at RT without multiple ligands. Besides, the temperature-dependent photoluminescence of Cs3 Cu2 I5 @MOF-74 may open up a new way to develop the applications of temperature sensors or other related optoelectronic devices.

How Do Smoking Status and Smoking Cessation Efforts Affect TB Recurrence After Successful Completion of Anti-TB Treatment? A Multicenter, Prospective Cohort Study With a 7-Year Follow-up in China.

INTRODUCTION: Many important risk factors are associated with tuberculosis (TB) recurrence; among them, smoking is the most common and modifiable behavioral factor. We aimed to assess the association of smoking status and cessation support during anti-TB treatment with subsequent TB recurrence. AIMS AND METHODS: A 7-year prospective cohort study was performed on 634 TB patients in China. The participants were grouped by smoking status at baseline. Cox proportional hazards models were applied to analyze the association between baseline characteristics and TB recurrence. The cumulative incidence of TB recurrence was estimated by Kaplan-Meier curves. RESULTS: Multivariable analysis showed that patients who continued smoking during anti-TB treatment were at higher risk for TB recurrence (hazard ratio = 3.45; 95% confidence interval: 1.54-7.73) than nonsmokers. Moreover, this risk remained significant even in those who stopped smoking during anti-TB treatment (hazard ratio = 2.75; 95% confidence interval: 1.47-5.14) than nonsmokers. The association between smoking and TB recurrence was stronger for smear-positive TB patients than for smear-negative TB patients. Among all the subgroups, patients who continued smoking had a higher TB recurrence rate over the 7-year follow-up than those who successfully quit during their anti-TB treatment (log-rank statistic, p < .01). With the increase in the number of cigarettes smoked daily, the TB recurrence risk also increased accordingly (log-rank statistic, p = .02). CONCLUSIONS: Our findings highlight the importance of incorporating effective smoking cessation intervention measures into TB services and call for continuous monitoring of TB recurrence. Among patients who continue smoking or have a history of smoking, special attention should be given to smear-positive patients and heavy smokers when monitoring recurrence. IMPLICATIONS: This study provides a comprehensive picture of the association of smoking behavior and cessation efforts with TB recurrence. It shows that patients who are nonsmokers have the lowest risk of recurrence and that ex-smokers have a lower risk of recurrence than current smokers. Moreover, patients who successfully quit smoking during TB treatment have a lower risk of recurrence than those who continue smoking. Health workers should provide cessation intervention, focus on TB patients with a history of smoking, and continuously monitor TB recurrence after the completion of anti-TB treatment, particularly for smear-positive TB patients.

Factors associated with non-compliance with breastfeeding recommendation: a retrospective survey in hepatitis B virus-infected mothers who had taken Nucleos(t)ide analogs during pregnancy.

BACKGROUND: We encourage Hepatitis B virus-infected mothers to breastfeed postpartum, even when continuing pregnancy category B nucleos(t)ide analogs (NAs) treatment. However, a large proportion of the Hepatitis B virus-infected mothers were noncompliant with this breastfeeding recommendation. This study aimed to investigate the factors associated with noncompliance with breastfeeding recommendation in Hepatitis B virus-infected mothers who had received NAs treatment during pregnancy. METHODS: A total of 155 mothers with chronic hepatitis B receiving NAs treatment for preventing mother-to-child transmission during the late gestation period were included and divided into exclusive breastfeeding (n = 63), mixed feeding (n = 34), and artificial feeding (n = 58) groups according to the postpartum feeding methods. Independent variables associated with feeding methods were analyzed using logistic regression analysis. RESULTS: Compared to the breastfeeding and mixed feeding groups, the artificial feeding group had significantly more multiparity, later postpartum timing of stopping NAs treatment, and a lower proportion of having knowledge of NAs medications (all P < 0.05). In addition, multivariable logistic regression analysis confirmed that multiparity, later postpartum timing of stopping NAs treatment, and lacking knowledge of medication were independent factors associated with noncompliance with breastfeeding recommendation. CONCLUSIONS: Hepatitis B virus-infected mothers who stopped NAs treatment at late postpartum period or had less knowledge of medication were more likely to be noncompliant with breastfeeding recommendation. Strengthening health education for participants taking NAs may be an important method to improve compliance with breastfeeding recommendation.

The safety of antiviral therapy and drug withdrawal for the prevention of mother-to-child transmission of HBV during pregnancy.

The efficacy of prenatal antiviral therapy (AVT) for preventing the vertical transmission of hepatitis B virus (HBV) is well demonstrated. However, data are limited regarding the safety of postpartum cessation of AVT, which may induce alanine aminotransferase (ALT) elevation. We aimed to investigate the necessity of prolonging maternal AVT after delivery. Chronic hepatitis B mothers at the immune-tolerant phase with HBV DNA levels >6 log10 IU/mL were prospectively enrolled and received AVT during the third trimester until delivery. Patients were offered to discontinue AVT either at delivery or postpartum week (PPW) 6. In addition, mothers who deferred AVT during pregnancy served as the control group. All mothers were followed until PPW 52 for clinical and virological parameters of hepatitis flares. Among 118 mothers recruited, 91 received AVT with 53 (group A) and 24 (group B) discontinue their treatment at delivery and PPW 6, respectively. Twenty-seven mothers who deferred AVT during pregnancy were followed as the control (group C). A total of 104 of 118 mothers who completed the study, 50% (52/104) had postpartum-elevated ALT levels, which were mild and moderate except 6 of 104 (5.77%) of patients had levels ≥5 times the upper limit of normal; 70% (36/52) of the ALT flares occurred within 12 weeks after delivery. In subgroup analyses, the frequency of ALT elevation was similar among the groups A vs B vs C (50.9% [27/53] vs 58.3% [14/24] vs 40.7% [11/27], respectively; P = .447), as well as the mean peak ALT level (108.4/74.1/126.7 U/L in groups A/B/C, respectively; P = .291). Although postpartum ALT flares were common for mothers with or without AVT during pregnancy, most cases of ALT elevation were mild to moderate. Our study observed that extending AVT to PPW 6 did not affect maternal outcomes and ATV should be discontinued at birth. Close monitoring is warranted as severe flares rarely occurred.

Exciton and bi-exciton mechanisms in amplified spontaneous emission from CsPbBr3 perovskite thin films.

We studied temperature-dependent amplified spontaneous emission (ASE) in CsPbBr3 perovskite thin films. For temperatures 180-360 K, a narrow-band lasing is observed. However, a new accompanying ASE band appears below 180 K, indicating a more complicated behavior. The two ASE bands are strongly correlated and in competition; they are assigned as exciton and bi-exciton recombination. We estimated the exciton binding energy (EB = 27.3 meV) and that of the bi-exciton, which is lower than the EB. The reduced effective mass of the exciton is estimated as µ = 0.11 me. This discovery identifies more details of the ASE phenomenon.

Investigation on binding energy and reduced effective mass of exciton in organic-inorganic hybrid lead perovskite films by a pure optical method.

The exciton binding energy and its reduced effective mass in hybrid lead perovskite, which play a key role in the process of excitons forming, largely determine the excellent optical properties of the perovskite materials and hence, the device performance. We introduce the systematic measurements on these two parameters of the organic-inorganic hybrid perovskite films of (MA/FA)Pb(Br/I)3 by a unique temperature and density-resolved optical spectroscopic method. The method is simple and straightforward, since it directly observes the exciton ionization and recombination. Our results describe the fundamental photoelectric properties for understanding the excellent performance of the perovskite materials.

Highly Efficient Organic Blue Electroluminescent Materials and Devices with Mesoscopic Structures.

Due to the difficulty in achieving high efficiency and high color purity simultaneously, blue emission is the limiting factor for the performance and stability of OLEDs. Since 2003, we have been working on organic light-emitting diodes (OLEDs), especially on blue light. After a series of molecular designs, novel strategies have been proposed from different aspects. At first, highly efficient deep blue emission could be achieved through molecular design with highly twisted structure to suppress fluorescence quenching and redshift. Deep blue emitters with high efficiency in solid state, a twisted structure with aggregation induced emission (AIE) characteristics was incorporated to inhibit molecular aggregation, and triplet-triplet fusion (TTF) and hybridized localized charge transfer (HLCT) were adopted to increase the ratio of triplet exciton used. Secondly, a highly efficient blue OLED could be achieved through improving charge transport. New electron transport materials (ETMs) with wide band gap were developed to control charge transport balance in devices. Thirdly, a highly efficient deep blue emission could be achieved through a mesoscopic structure of out-coupling layer. A mesoscopic photonic structured organic thin film was fabricated on the top of metal electrode by self-aggregation in order to improve the light out-coupling efficiency.

Crown-Assisted CsCu2I3 Growth and Trap Passivation for Perovskite Light-Emitting Diodes.

Copper (Cu)-based perovskites are promising for lead-free perovskite light-emitting diodes (PeLEDs). However, it remains a significant challenge to achieve high performance devices due to the nonradiative loss caused by the disordered crystallization and lack of passivation. Crown ethers are known to form host-guest complexes by the interaction between C-O-C groups and certain cations, and 18-crown-6 (18C6) with an appropriate complementary size can interact with Cs+ and Cu+ cations. Herein, we studied the interaction between CsCu2I3 and two crowns with the same cyclic size, 18C6 and dibenzo-18-crown-6 (D18C6). Particularly, D18C6 can reduce the nonradiative recombination rate of CsCu2I3 film by passivating the defects and optimizing the film morphology effectively. The room mean square (RMS) decreased from 5.06 to 2.95 nm, and the PLQY was promoted from 4.71% to 19.9%. Besides, D18C6 can also decrease the barrier of hole injection. The PeLEDs based on D18C6-modified CsCu2I3 realized noticeable improvement with a maximum luminance and EQE of 583 cd/m2 and 0.662%, respectively.

Passivating A-Site and X-Site Vacancies Simultaneously via N-Heterocyclic Amines for Efficient Cs2AgBiBr6 Solar Cells.

To address the toxicity and stability issues of traditional lead halide perovskite solar cells (PSCs), the development of lead-free PSCs, such as Cs2AgBiBr6 solar cells, is of great significance. However, due to the low defect formation energy of Cs2AgBiBr6, a large number of vacancies, including A-site vacancies and X-site vacancies, form during the fabrication process of the Cs2AgBiBr6 film, which seriously damage the performance of the devices. The traditional phenylethylammonium (PEA) cation, mainly focusing on passivating A-site vacancies, is incapable of reducing X-site vacancies and so results in a limited performance improvement in Cs2AgBiBr6 solar cells. Herein, inspired by the capability of the Lewis base to coordinate with metal cations, a series of N-heterocyclic amines are introduced to serve as a dual-site passivator, reducing A-site and X-site vacancies at the same time. The highest power conversion efficiency of modified Cs2AgBiBr6 solar cells has been increased 36% from 1.10 to 1.50%. Further investigation reveals that the higher electron density of additives would lead to a stronger interaction with metal cations like Ag+ and Bi3+, thus reducing more X-site defects and improving carrier dynamics. Our work provides a strategy for passivating perovskite with various kinds of defects and reveals the connection between the coordination capability of additives and device performance enhancement, which could be instructive in improving the performance of lead-free PSCs.

A crystal capping layer for formation of black-phase FAPbI3 perovskite in humid air.

Black-phase formamidinium lead iodide (α-FAPbI3) perovskites are the desired phase for photovoltaic applications, but water can trigger formation of photoinactive impurity phases such as δ-FAPbI3. We show that the classic solvent system for perovskite fabrication exacerbates this reproducibility challenge. The conventional coordinative solvent dimethyl sulfoxide (DMSO) promoted δ-FAPbI3 formation under high relative humidity (RH) conditions because of its hygroscopic nature. We introduced chlorine-containing organic molecules to form a capping layer that blocked moisture penetration while preserving DMSO-based complexes to regulate crystal growth. We report power conversion efficiencies of >24.5% for perovskite solar cells fabricated across an RH range of 20 to 60%, and 23.4% at 80% RH. The unencapsulated device retained 96% of its initial performance in air (with 40 to 60% RH) after 500-hour maximum power point operation.

Sub-Second Long Lifetime Triplet Exciton Reservoir for Highly Efficient and Stable Organic Light-Emitting Diode.

In organic light-emitting diode (OLED), achieving high efficiency requires effective triplet exciton confinement by carrier-transporting materials, which typically have higher triplet energy (ET) than the emitter, leading to poor stability. Here, an electron-transporting material (ETM), whose ET is 0.32 eV lower than that of the emitter is reported. In devices, it surprisingly exhibits strong confinement effect and generates excellent efficiency. Additionally, the device operational lifetime is 4.9 times longer than the device with a standard ETM, 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl) phenyl (whose ET 0.36 eV is higher than the emitter). This anomalous finding is ascribed to the exceptionally long triplet state lifetime (≈0.2 s) of the ETM. It is named as long-lifetime triplet exciton reservoir effect. The systematic analysis reveals that the long triplet lifetime of ETM can compensate the requirement for high ET with the help of endothermic energy transfer. Such combination of low ET and long lifetime provides equivalent exciton confinement effect and high molecular stability simultaneously. It offers a novel molecular design paradigm for breaking the dilemma between high efficiency and prolonged operational lifetime in OLEDs.

[Organic solar cell based on alkylthiol/Au self-assembly film as buffer layer].

The interface modification between the organic active layer and the inorganic electrode affects the performance of organic solar cell (OSC). A buffer layer of alkylthiol (ethanethiol, hexanethiol, dodecanethiol)/Au self-assembly layer was introduced into OSC to substitute Poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) layer, in order to improve the organic/inorganic interface. We fabricated devices with structure of "ITO/Au (annealed Au film of 2 nm)-thiol self assembly layer/poly(3-hexylthiophene) : 1-(3-methoxycarbonyl) -propyl-1-phenyl-(6,6)C61(P3HT : PCBM) /LiF/Al". After alkanethiol self-assembling, the alkanethiol prevented exciton quenching owe to direct contact between the Au NPs and the active layer. We studied the impact of alkanethiol with different chain length on device performance. With? the? growth? of? the? alkyl chain, the coverage of the thiol on Au NPs got better, and the device performance become better. In the OSC with dodecane-thiol/Au (2 nm Au film annealed) self-assembly film, the short-circuit current increases from 5.19 mA x cm(-2) to 6.24 mA x cm(-2).

Expanding the Absorption of Double Perovskite Cs2AgBiBr6 to NIR Region.

The toxicity of lead-based halide perovskites hampers broad application in optoelectronics. The lead-free perovskite Cs2AgBiBr6 is considered a promising candidate, owing to its long carrier lifetime and outstanding stability. However, the relatively large bandgap hinders its absorption in the visible region and thus the application of its photoelectric properties in the visible and near-infrared (NIR) regions. Therefore, the expansion of absorption to the longer wavelengths, even the NIR region, makes sense for solar cells and photodetector applications. Facile elemental doping or substitution of Cs2AgBiBr6 makes it potentially desirable for applications in both visible and NIR regions. As a result, band-edge adjustment to expand the absorption onset or trace deep-energy-level doping with a new intermediate band was achieved. Here, we summarize the elemental doping results and review the potential application of Cs2AgBiBr6 from these two aspects and give constructive perspectives for further development of lead-free perovskite.

Superstable CsxSnBrx+2@CsBr Nanocrystals with Over 1200 h of Half-Value PLQY in Air.

Tin-based perovskites comprise one of the preferred nontoxic alternatives to Pb-based perovskites due to their desirable optoelectronic properties. However, there remains a crucial stability problem due to the property of Sn2+ oxidation. In this study, we reported stable tin-based perovskite nanocrystals (NCs) using stannous acetate as the Sn2+ source because of its stronger Sn-O bonding. To prevent the oxidation of Sn2+, a thin layer of CsBr coverage was formed in situ; tin-based perovskite NCs, CsxSnBrx+2@CsBr (1 < x < 4), show a high photoluminescence quantum yield (PLQY) of 78.2% and high stability. The measured lifetime of PLQY decrease to half of the initial value is ∼1287 h under ambient conditions and ∼2200 h under a nitrogen atmosphere, respectively. Furthermore, the as-fabricated light-emitting diodes based on CsxSnBrx+2@CsBr NCs as the emitting layer exhibit a maximum luminescence of 16 cd/m2 and an external quantum efficiency of 0.035% with peaks at 451 and 615 nm, corresponding to the emissions of CsBr and CsxSnBrx+2, respectively. This work provided a new way to obtain stable Sn-based perovskite NCs and exhibited their potential for application in white light-emitting diodes (LEDs).

Separating Crystal Growth from Nucleation Enables the In Situ Controllable Synthesis of Nanocrystals for Efficient Perovskite Light-Emitting Diodes.

Colloidal perovskite nanocrystals (PNCs) display bright luminescence for light-emitting diode (LED) applications; however, they require post-synthesis ligand exchange that may cause surface degradation and defect formation. In situ-formed PNCs achieve improved surface passivation using a straightforward synthetic approach, but their LED performance at the green wavelength is not yet comparable with that of colloidal PNC devices. Here, it is found that the limitations of in situ-formed PNCs stem from uncontrolled formation kinetics: conventional surface ligands confine perovskite nuclei but fail to delay crystal growth. A bifunctional carboxylic-acid-containing ammonium hydrobromide ligand that separates crystal growth from nucleation is introduced, leading to the formation of quantum-confined PNC solids exhibiting a narrow size distribution. Controlled crystallization is further coupled with defect passivation using deprotonated phosphinates, enabling improvements in photoluminescence quantum yield to near unity. Green LEDs are fabricated with a maximum current efficiency of 109 cd A-1 and an average external quantum efficiency of 22.5% across 25 devices, exceeding the performance of their colloidal PNC-based counterparts. A 45.6 h operating half-time is further documented for an unencapsulated device in N2 with an initial brightness of 100 cd m-2 .