ABSTRACT
The two-step sequential deposition is a commonly used method by researchers for fabricating perovskite solar cells (PSCs) due to its reproducibility and tolerant preparation conditions. However, the less-than-favorable diffusive processes in the preparation process often result in subpar crystalline quality in the perovskite films. In this study, we employed a simple strategy to regulate the crystallization process by lowering the temperature of the organic-cation precursor solutions. By doing so, we minimized interdiffusion processes between the organic cations and pre-deposited lead iodide (PbI2) film under poor crystallization conditions. This allowed for a homogenous perovskite film with improved crystalline orientation when transferred to appropriate environmental conditions for annealing. As a result, a boosted power conversion efficiency (PCE) was achieved in PSCs tested for 0.1 cm2 and 1 cm2, with the former exhibiting a PCE of 24.10% and the latter of 21.56%, compared to control PSCs, which showed a PCE of 22.65% and 20.69%, respectively. Additionally, the strategy increased device stability, with the cells holding 95.8% and 89.4% of the initial efficiency even after 7000 h of aging under nitrogen or 20-30% relative humidity and 25 °C. This study highlights a promising low-temperature-treated (LT-treated) strategy compatible with other PSCs fabrication techniques, adding a new possibility for temperature regulation during crystallization.
ABSTRACT
BACKGROUND & OBJECTIVES: Angiogenesis plays an essential role in tumor growth, invasion, and metastasis. Vascular endothelial growth factor(VEGF) is regarded the most important angiogenetic growth factor and it has been found in many kinds of tumors that its high expression can promote tumor progression and effect prognosis. However, there was few reports about the relationship between the VEGF expression and the progression and prognosis of the patients with esophageal carcinoma. The current study was designed to investigate the relationship between VEGF expression and the prognosis of patients with esophageal squamous cell carcinoma. METHODS: The expression of VEGF protein in 72 resected specimens from the patients with esophageal squamous cell carcinoma were examined immunohistochemically, and its effects on postoperative recurrence and survival of the patients were analyzed retrospectively. RESULTS: Fourty-five out of 72 (62.5%) samples were positive for VEGF expression. The VEGF-positive patients tend to occur postoperative recurrence than VEGF-negative patients (P < 0.001). The median survival time and 1, 3, 5-year survival rate of VEGF-positive patients was lower than those of VEGF-negative patients. And the Kaplan-Meier survival curve was worse in VEGF-positive groups than in VEGF-negtive groups(Log rank test, P = 0.021). Multivariate analysis revealed that VEGF was not an independent factor that impact on the prognosis (P > 0.05). CONCLUSIONS: The high expression of VEGF in esophageal squamous cell carcinoma may promote the tumor progression and lead to dismal prognosis. However, the value of VEGF expression for judging prognosis need further study.
