Flexible and transparent thin-film silicon solar cells were fabricated and optimized for building-integrated photovoltaics and bifacial operation. A laser lift-off method was developed to avoid thermal damage during the transfer of light-scattering structures onto colorless polyimide substrates and thus enhance front-incidence photocurrent, while a dual n-type rear window layer was introduced to reduce optical losses, facilitate electron transport for rear incidence, and thus enhance performance during bifacial operation. The introduction of the window layer increased the rear-to-front power conversion efficiency ratio to ~86%. The optimized bifacial power conversion efficiency for front and rear irradiances of 1 and 0.3 sun, respectively, equaled 6.15%, and the average transmittance within 500–800 nm equaled 36.9%. Additionally, the flexible and transparent solar cells fabricated using laser lift-off exhibited good mechanical reliability (i.e., sustained 500 cycles at a bending radius of 6 mm) and were therefore suitable for building-integrated photovoltaics.

According to the Codex committee, the maximum allowable level for lead in fruits is 0.1 mg/kg. This survey was conducted as a surveillance program following the establishment of safety guideline for fruits in Korea. Concentrations of lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg) were measured in 927 samples using a ICP-MS and a mercury analyzer. The recoveries of microwave digestion method were 86.0-110.4% for Pb, 81.0-104.0% for Cd and 82.0-104.7% for As by standard addition method. The recovery of direct mercury analyzer was 106.5% for Hg. The average levels of Pb in µg/kg were 10.0±12.8 for apple, 8.8±10.9 for pear, 4.1±4.4 for persimmons, 14.9±12.3 for mandarin, 7.1±6.5 for orange, 3.1±3.3 for banana, 8.8±8.9 for kiwi, and 9.3±9.7 for mango. The average levels of Cd in µg/kg were 0.4±0.3 for apple, 2.0±1.6 for pear, 0.3±0.3 for persimmon, 0.1±0.1 for mandarin, 0.1±0.1 for orange, 1.3±1.8 for banana, 0.5±0.5 for kiwi, and 0.7±0.6 for mango. The average levels of As in µg/kg were 2.0±2.1 for apple, 1.2±1.3 for pear, 1.5±1.1 for persimmon, 0.8±0.3 for mandarin, 1.0±0.5 for orange, 1.8±1.2 for banana, 1.6±1.5 for kiwi, and 1.5±1.2 for mango. The average levels of Hg in µg/kg were 0.5±0.4 for apple, 0.3±0.2 for pear, 0.2±0.1 for persimmon, 0.2±0.1 for mandarin, 0.2±0.1 for orange, 0.2±0.0 for banana, 0.2±0.2 for kiwi, and 0.6±0.2 for mango. Based on the Korean public nutrition report 2005, these levels (or amounts) are calculated only at 0.17% for Pb, 0.013% for Cd and 0.006% for Hg of those presented in provisional tolerable weekly Intake (PTWI) which has been established by FAO/WHO. Therefore, the levels presented here are presumed to be adequately safe.

Transparent hydrogenated amorphous silicon solar cells were fabricated using a p-type window layer of molybdenum oxide (MoOx) for building-integrated photovoltaic (BIPV) windows. The MoOx layer was prepared with oxygen flow ratios from 0.03 to 0.21 by reactive sputtering, and the PV performance was improved using MoOx with an oxygen flow ratio of 0.09 because of the lower carrier recombination and parasitic absorption in the p layer. Additionally, we optimized the cell by introducing a MoOx bilayer, and the power conversion efficiency of the cell using an optimized MoOx bilayer was enhanced by boosted open circuit voltage through facilitating hole transfer. To realize the application of the BIPV window, we manufactured a monolithic connected solar module using the laser scribing process, and the cell-to-module loss was approximately 22.9%. Because MoOx remained after the P2 scribing process, residual MoOx played a role in the deterioration of the series resistance.

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