We present a novel approach to fabricate flexible organic solar cells without indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). We use junctionfree metal nanonetworks (NNs) as transparent electrodes. The metal NNs are monolithically etched using nanoscale shadow masks, and they exhibit excellent optoelectronic performance. Furthermore, the optoelectrical properties of the NNs can be controlled by both the initial metal layer thickness and NN density. Hence, with an extremely thin silver layer, the appropriate density control of the networks can lead to high transmittance and low sheet resistance. Such NNs can be utilized for thin film devices without planarization by conductive materials such as PEDOT:PSS. As a result, we successfully fabricate a highly efficient flexible organic solar cell with a power conversion efficiency (PCE) of 10.6% and high device yield (93.8%) on PEDOT-free and ITO-free transparent electrodes. Furthermore, the flexible solar cell retains 94.3% of the initial PCE even after 3000 bending stress tests (strain: 3.13%).

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Congenital heart defect (CHD) is common in infants with Down syndrome (DS), which is the principle cause of mortality. However, there is no data available for the frequency and types of CHD in infants with DS in Korea. We investigated the frequency of CHD in infants with DS in Korea. After the survey on birth defects was conducted throughout the country, the prevalence of CHD in DS in 2005-2006 was calculated. This study was conducted based on the medical insurance claims database of the National Health Insurance Corporation. The number of total births in Korea was 888,263 in 2005-2006; of them, 25,975 cases of birth defects were identified. The prevalence of DS was 4.4 per 10,000 total births, accounting for 1.5% of all birth defects. Of the 394 infants with DS, 224 (56.9%) had a CHD. Atrial septal defect was the most common defect accounting for 30.5% of DS followed by ventricular septal defect (19.3%), patent duct arteriosus (17.5%), and atrioventricular septal defect (9.4%). Our study will be helpful to demonstrate the current status of DS and to identify the distribution of CHD in infants with DS in Korea.

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