Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous–titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid–stabilized tin(IV) oxide quantum dots (paa-QD-SnO2) on the compact–titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL–perovskite interface. The use of paa-QD-SnO2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively. Description Tailoring tin oxide layers Mesoporous titanium dioxide is commonly used as the electron transport layer in perovskite solar cells, but electron transport layers based on tin(IV) oxide quantum dots could be more efficient, with a better-aligned conduction band and a higher carrier mobility. Kim et al. show that such quantum dots could conformally coat a textured fluorine-doped tin oxide electrode when stabilized with polyacrylic acid. Improved light trapping and reduced nonradiative recombination resulted in a certified power conversion efficiency of 25.4% and high operational stability. In larger-area minimodules, active areas as high as 64 square centimeters maintained certified power conversion efficiencies of more than 20%. —PDS Polymer-stabilized tin oxide nanoparticles suppress recombination at the electron-transport layer–perovskite interface.

Conformal quantum dot–SnO2 layers as electron transporters for efficient perovskite solar cells

Photoluminescence blinking—random switching between states of high (ON) and low (OFF) emissivities—is a universal property of molecular emitters found in dyes, polymers, biological molecules and artificial nanostructures such as nanocrystal quantum dots, carbon nanotubes and nanowires. For the past 15 years, colloidal nanocrystals have been used as a model system to study this phenomenon. The occurrence of OFF periods in nanocrystal emission has been commonly attributed to the presence of an additional charge, which leads to photoluminescence quenching by non-radiative recombination (the Auger mechanism). However, this ‘charging’ model was recently challenged in several reports. Here we report time-resolved photoluminescence studies of individual nanocrystal quantum dots performed while electrochemically controlling the degree of their charging, with the goal of clarifying the role of charging in blinking. We find that two distinct types of blinking are possible: conventional (A-type) blinking due to charging and discharging of the nanocrystal core, in which lower photoluminescence intensities correlate with shorter photoluminescence lifetimes; and a second sort (B-type), in which large changes in the emission intensity are not accompanied by significant changes in emission dynamics. We attribute B-type blinking to charge fluctuations in the electron-accepting surface sites. When unoccupied, these sites intercept ‘hot’ electrons before they relax into emitting core states. Both blinking mechanisms can be electrochemically controlled and completely suppressed by application of an appropriate potential.

https://absimage.aps.org/image/MAR12/MWS_MAR12-2011-002227.pdf

Two types of luminescence blinking revealed by spectroelectrochemistry of single quantum dots

Since the report in 2012 of a solid-state perovskite solar cell (PSC) with a power-conversion efficiency (PCE) of 9.7% and a stability of 500 h, intensive efforts have been made to increase the certified PCE, reaching 25.2% in 2019. The PCE of PSCs now exceeds that of conventional thin-film solar-cell technologies, and the rate at which this increase has been achieved is unprecedented in the history of photovoltaics. Moreover, the development of moisture-stable and heat-stable materials has increased the stability of PSCs. Small-area devices ( 100 cm2) substrates required for commercialization. Thus, materials and methods need to be developed for coating large-area PSCs. In this Review, we discuss solution-based and vapour-phase coating methods for the fabrication of large-area perovskite films, examine the progress in performance and the parameters affecting the properties of large-area coatings, and provide an overview of the methodologies for achieving high-efficiency perovskite solar modules. The scalable fabrication of perovskite solar cells and solar modules requires the development of new materials and coating methods. In this Review, we discuss solution-based and vapour-phase coating methods for large-area perovskite films and examine the progress in performance and the parameters affecting large-area coatings.

Scalable fabrication and coating methods for perovskite solar cells and solar modules

Recent Progresses on Defect Passivation toward Efficient Perovskite Solar Cells

Current-density-voltage (J-V) hysteresis in perovskite solar cells (PSCs) is a critical issue because it is related to power conversion efficiency and stability. Although parameters affecting the hysteresis have been already reported and reviewed, little investigation is reported on scan-direction-dependent J-V curves depending on perovskite composition. This review investigates J-V hysteric behaviors depending on perovskite composition in normal mesoscopic and planar structure. In addition, methodologies toward hysteresis-free PSCs are proposed. There is a specific trend in hysteresis in terms of J-V curve shape depending on composition. Ion migration combined with nonradiative recombination near interfaces plays a critical role in generating hysteresis. Interfacial engineering is found to be an effective method to reduce the hysteresis; however, bulk defect engineering is the most promising method to remove the hysteresis. Among the studied methods, KI doping is proved to be a universal approach toward hysteresis-free PSCs regardless of perovskite composition. It is proposed from the current studies that engineering of perovskite film near the electron transporting layer (ETL) and the hole transporting layer (HTL) is of vital importance for achieving hysteresis-free PSCs and extremely high efficiency.

On the Current-Voltage Hysteresis in Perovskite Solar Cells: Dependence on Perovskite Composition and Methods to Remove Hysteresis

Electronic doping is a promising approach to modulating the optoelectronic properties of semiconductors, but its effect on optoelectronic behaviors of halide perovskites remains controversial. Here, we comprehensively investigate the impact of Pb substitution in n-type CsPbIBr2 perovskite by utilizing monovalent Ag, divalent Zn, and trivalent Sb. Our findings reveal that the trap densities in doped CsPbIBr2 films are in the order of Ag < Zn < Sb. Compared with the pristine CsPbIBr2, the Ag-doped perovskite features a significantly reduced phase separation; however, the Sb doping accelerates halide segregation, and Zn exerts a negligible influence. The p-doping effect from monovalent Ag can shift the Fermi level of CsPbIBr2 toward the intrinsic midgap, which helps prevent the formation of ionic defects and reduce the migration of halide ions in the perovskite lattice. Through combing the density functional theory simulation, this study discloses the correlation between valence-controlled metal doping and phase segregation, providing a guideline for judiciously doping mixed-halide perovskites for optoelectronic applications. 

Valence-Regulated Metal Doping of Mixed-Halide Perovskites to Modulate Phase Segregation and Solar Cell Performance

Cyclic GMP-AMP synthase (cGAS) is a crucial DNA sensor and plays an important role in host antiviral innate immune responses. During hepatitis B virus (HBV) infection, the cGAS signaling pathway can suppress HBV replication. As an important regulatory protein of HBV, hepatitis B virus X protein (HBx) may serve as an antagonistic character to the cGAS/STING signaling pathway. In this study, we aim to investigate the functional role of HBx in the cGAS/STING signaling pathway.The effects of HBx on IFN-β promoter activity were measured by Dual-luciferase reporter assays. Ubiquitination and autophagy were analyzed by Western-blot and Co-immunoprecipitation assays.Our results show that HBx down-regulates IFN-I production by directly promoting ubiquitination and autophagy degradation of cGAS.HBV can antagonize host cGAS DNA sensing to promote HBV replication and provide novel insights to develop novel approaches against HBV infection. 

/pdf/hbx-inhibits-dna-sensing-signaling-pathway-via-30xo3q7j.pdf

HBx inhibits DNA sensing signaling pathway via ubiquitination and autophagy of cGAS

Perovskite solar cells (PSCs) have witnessed an unprecedentedly rapid development, especially in terms of power conversion efficiency (PCE). However, the solution‐processed perovskite films inevitably possess numerous crystallographic defects (e.g., halide vacancies), which has been shown to incur non‐radiative charge recombination and ion migration, thus limiting the enhancement of the PCE and stability of PSCs. Here, a novel dual metal (i.e., divalent and monovalent metal ions) modification strategy is reported for simultaneously reducing the defects, immobilizing the halide anions, and preventing ion loss from perovskite during post‐annealing process. Accordingly, this strategy significantly reduces non‐radiative recombination, enhancing the PCE by ≈12% and mitigating the current density‐voltage (J–V) hysteresis effect in resultant devices compared to undoped counterparts. As a result, a champion PCE exceeding 22% and a high open‐circuit voltage (Voc) of 1.16 V is obtained for dual metal ions‐modified PSCs. The optimized devices also exhibit extended lifespan upon the dual metal treatment. The study provides a new defect engineering strategy toward more efficient and stable perovskite photovoltaics.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adfm.202208077

Dual Metal‐Assisted Defect Engineering towards High‐Performance Perovskite Solar Cells

• Circulating miR-124-3p and miR-377-3p may constitute promising biomarkers for the diagnosis of SLE . • The levels of miRNA-124-3p and miRNA-377-3p in PBMCs were significantly upregulated. • miR-377-3p is independently correlated with SLE. • Plasma miR-124-3p is independently associated with the remission rate of SLE. To explore the clinical value of miR-124-3p and miR-377-3p in plasma, and to examine whether these microRNAs can serve as biomarkers for systemic lupus erythematosus. Samples from 50 patients with SLE and 47 healthy individuals were collected from the Rheumatology and Immunology Department at the Second Affiliated Hospital of Chongqing Medical University. The expression of miR-124-3p and miR-377-3p in peripheral blood mononuclear cells (PBMCs) and serum were determined by quantitative reverse-transcription PCR (RT-PCR). We then further analyzed the associations between these microRNAs and clinically relevant indicators. We employed receiver operating characteristic (ROC) curves and the area under the ROC curves (AUCs) to validate the diagnostic value of miR-124-3p and miR-377-3p. The expression of miR-124-3p and miR-377-3p was significantly upregulated in PBMCs and serum from SLE patients compared with the normal control group ( P < 0.05). ROC curve analysis indicated that plasma miR-124-3p and miR-377-3p were thus candidate diagnostic biomarkers for SLE, with AUCs of 0.714 (95% CI, 0.610 to 0.820, P < 0.05) and 0.705 (95% CI, 0.600 to 0.809, P < 0.05), respectively. Furthermore, the combined diagnostic efficiency of miR-124-3p and miR-377-3p was higher than that for miR-124-3p or miR-377-3p alone, and the AUCs for miR-124-3p and miR-377-3p in plasma were higher than in PBMCs. Plasma miR-124-3p expression was also associated with various clinicopathological parameters such as antiC1q and C3. Binary logistic regression analysis revealed that the expression of miR-377-3p was an independent predictor for SLE, and the plasma miR-124-3p was independently associated with the remission rate of SLE. Circulating miR-124-3p and miR-377-3p may constitute promising biomarkers for the diagnosis of SLE. 

Weijian Chen

Papers

Valence-Regulated Metal Doping of Mixed-Halide Perovskites to Modulate Phase Segregation and Solar Cell Performance

HBx inhibits DNA sensing signaling pathway via ubiquitination and autophagy of cGAS

Dual Metal‐Assisted Defect Engineering towards High‐Performance Perovskite Solar Cells

Novel microRNA biomarkers of systemic lupus erythematosus in plasma: miR-124-3p and miR-377-3p.

Energy Funneling in Quasi-2D Ruddlesden–Popper Perovskites: Charge Transfer versus Resonant Energy Transfer