RESUMO
Perovskite solar cells have shown a rapid increase of performance and overcome the threshold of 20% power conversion efficiency (PCE). The main issues hampering commercialization are the lack of deposition methods for large areas, missing long-term device stability and the toxicity of the commonly used Pb-based compounds. In this work, we present a novel chemical vapor deposition (CVD) process for Pb-free air-stable methylammonium bismuth iodide (MBI) layers, which enables large-area production employing close-coupled showerhead technology. We demonstrate the influence of precursor rates on the layer morphology as well as on the optical and crystallographic properties. The impact of substrate temperature and layer thickness on the morphology of MBI crystallites is discussed. We obtain smooth layers with lateral crystallite sizes up to 500 nm. Moreover, the application of CVD-processed MBI layers in non-inverted perovskite solar cells is presented.
RESUMO
Fabrication of transition metal dichalcogenides (TMDCs) via metalorganic chemical vapor deposition (MOCVD) represents one of the most attractive routes to large-scale 2D material layers. Although good homogeneity and electrical conductance have been reported recently, the relation between growth parameters and photoluminescence (PL) intensity-one of the most important parameters for optoelectronic applications-has not yet been discussed for MOCVD TMDCs. In this work, MoS2 is grown via MOCVD on sapphire (0001) substrates using molybdenum hexacarbonyl (Mo(CO)6, MCO) and di-tert-butyl sulphide as precursor materials. A prebake step under H2 atmosphere combined with a reduced MCO precursor flow increases the crystal grain size by one order of magnitude and strongly enhances PL intensity with a clear correlation to the grain size. A decrease of the linewidth of both Raman resonances and PL spectra down to full width at half maxima of 3.2 cm-1 for the E 2g Raman mode and 60 meV for the overall PL spectrum indicate a reduced defect density at optimized growth conditions.
RESUMO
BACKGROUND: There is a need for controlled trials to guide the perioperative management of patients undergoing endoscopic sinus surgery (ESS). The authors performed a pilot multicenter trial to compare two types of saline delivery devices in this population. METHODS: Patients were randomized to high volume saline irrigation with a squeeze bottle and low volume saline spray after ESS in patients with chronic rhinosinusitis (CRS). Surgeons were blinded to treatment, and one-month postoperative scores for sinonasal outcomes [Sinonasal Outcome Test-22 (SNOT-22)] scale, nasal and sinus symptom score (NSS), and perioperative sinus endoscopy (POSE) scale were compared with preoperative scores. RESULTS: Nine centers provided data for 86 patients. All three outcomes measures improved significantly for both groups. Saline spray: SNOT-22 48.8 versus. 23.7, treatment effect 25.1 (95% confidence interval [CI], 17.9-32.2), POSE 21.1 versus. 8.4, treatment effect 12.7 (95% CI, 9.2-16.1), and NSS 8.2 versus 5.0, treatment effect 3.1 (95% CI, 1.4-4.9) pre- and postoperatively, respectively (all p < 0.0001). Squeeze bottle: SNOT-22 49.5 versus 23.6, treatment effect 25.9 (95% CI, 20.3-31.6), POSE 18.6 versus 9.2, treatment effect 9.3, (95% CI 6.7-12.0), and NSS 9.0 versus 5.7, treatment effect 3.3 (95% CI, 2.3-4.3) pre- and postoperatively, respectively (all p < 0.0001). Analysis of variance did not identify a difference between the two treatment groups. Subgroup analysis based on preoperative disease severity did not change the nonassociation of saline bottle with outcome measures. Post hoc sample size calculation determined that 176 patients is required to detect an 8.9-point difference in SNOT-22 scores. CONCLUSION: In this pilot multicenter trial examining patients with chronic rhinosinusitis undergoing ESS, both squeeze bottle and saline spray showed significant improvement in SNOT-22, POSE, and NSS scores at one-month postoperatively. Because the study was nonpowered, we cannot rule out a potential difference between the two treatment groups.
