developed silicon solar cells. It shows the great potential of PSCs as the dominator of next-generation photovoltaics. Whereas, during the evolution of PSC development, the metal oxide electron transporting layer (ETL), as well as the ETL/perovskite interface, [11][12][13][14] has always been an issue in regard to photovoltaic efficiency and device stability. [8] Derived from dye-sensitized solar cells (DSSCs), the combination of compact and mesoporous TiO 2 has been commonly utilized as ETLs during the early studies of PSCs. [15] But a high sintering temperature of ≈500 °C is normally required for the fabrication process, which is high energy consumption and incompatible with scalable depositions on flexible substrates. Worse still, TiO 2 is highly photocatalytic active under ultraviolet (UV) irradiation that severely hampers the long-term stability of PSCs under illumination. [16][17][18][19][20][21][22] Later on, a new ETL, SnO 2 , has been developed as a better candidate, due to its low-temperature processability [23] and high sustainability under UV illumination. [24][25][26][27] More importantly, SnO 2 film has superior crystallinity and carrier mobility in comparison to TiO 2 . [28,29] Thus, a single layer of compact SnO 2 could enable an efficient charge transport and suppressed recombination losses at the ETL/perovskite interface. Benefiting from these advantages, PSCs based on SnO 2 as ETL have reached PCE of 25.2% to date. [30] Whereas, considerable amount of oxygen vacancies on the SnO 2 surface would act as deep traps to capture the photogenerated carriers, which causes hysteresis and instability of the device. [31][32][33][34] And this intrinsic defect of SnO 2 needs to be resolved for a further PCE breakthrough of PSCs.In recent years, significant attempts of defect-passivation have been made to decrease the oxygen vacancies and trap states on SnO 2 surface. [35][36][37][38] Among them, n-type fullerene derivatives represent one of the most studied and efficacious passivator, [39][40][41][42] due to the ease of forming coordinate bonds between carboxylate group and SnO 2 surface. In addition, fullerene derivative is a common electron acceptor in organic solar cells (OSCs), [43] which grants an effective electron extraction from the perovskite active layer to ETL, thus contributing to higher PSC performances. Nevertheless, it should be noticed that π-cage structures of fullerene derivatives are prone to self-aggregate, [44] which strongly affects the validity and SnO 2 has been universally applied as electron transporting layer (ETL) towards the fabrication of highly efficient perovskite solar cells (PSCs), owing to its unique advantages including low-temperature solution-processability, high optical, transmittance and good electrical conductivity. Uncoordinated Sn-dangling bonds on SnO 2 surface exist as deep traps to capture the photogenerated carriers, causing hysteresis and device instability. Fullerene derivatives, though being widely utilized as the passivator for SnO 2 , are highly prone to...

The electron transport layer (ETL) has an important influence on the power conversion efficiency (PCE) and stability of n-i-p planar perovskite solar cells (PSCs). This paper presents an N-type semiconductor material, (CH 3) 2 Sn(COOH) 2 (abbreviated as CSCO) that is synthesized and prepared for the first time as an ETL for n-i-p planar PSCs, which leads to a high PCE of 22.21% after KCl treatment, one of the highest PCEs of n-i-p planar PSCs to date. Further analysis reveals that the high PCE is attributed to the excellent conductivity of CSCO because of its more delocalized electron cloud distribution due to its unique −O=C−O− group, and to the defect passivation of the Cs 0.05 (FA 0.85 MA 0.15) 0.95 Pb(I 0.85 Br 0.15) 3 (denoted as CsFAMA) perovskite through the interaction between the O (Sn) atoms of CSCO and the Pb (halogen) atoms of CsFAMA at CSCO/CsFAMA interface, while the traditional ETL materials such as SnO 2 film lack this function. In addition to the high PCE, the optimal PSCs using CSCO as ETL show remarkable stability, retaining over 83% of its initial PCE without encapsulation after 130 days of storage in ambient conditions (≈25 °C at ≈40% humidity), much better than the traditional SnO 2-based n-i-p PSCs.

BackgroundStaphylococcus epidermidis (SE) has emerged as one of the most important causes of nosocomial infections. The SaeRS two-component signal transduction system (TCS) influences virulence and biofilm formation in Staphylococcus aureus. The deletion of saeR in S. epidermidis results in impaired anaerobic growth and decreased nitrate utilization. However, the regulatory function of SaeRS on biofilm formation and autolysis in S. epidermidis remains unclear.ResultsThe saeRS genes of SE1457 were deleted by homologous recombination. The saeRS deletion mutant, SE1457ΔsaeRS, exhibited increased biofilm formation that was disturbed more severely (a 4-fold reduction) by DNase I treatment compared to SE1457 and the complementation strain SE1457saec. Compared to SE1457 and SE1457saec, SE1457ΔsaeRS showed increased Triton X-100-induced autolysis (approximately 3-fold) and decreased cell viability in planktonic/biofilm states; further, SE1457ΔsaeRS also released more extracellular DNA (eDNA) in the biofilms. Correlated with the increased autolysis phenotype, the transcription of autolysis-related genes, such as atlE and aae, was increased in SE1457ΔsaeRS. Whereas the expression of accumulation-associated protein was up-regulated by 1.8-fold in 1457ΔsaeRS, the expression of an N-acetylglucosaminyl transferase enzyme (encoded by icaA) critical for polysaccharide intercellular adhesin (PIA) synthesis was not affected by the deletion of saeRS.ConclusionsDeletion of saeRS in S. epidermidis resulted in an increase in biofilm-forming ability, which was associated with increased eDNA release and up-regulated Aap expression. The increased eDNA release from SE1457ΔsaeRS was associated with increased bacterial autolysis and decreased bacterial cell viability in the planktonic/biofilm states.