Hydrog enated amorphous∕crystalline silicon “heterojunction with intrinsic thin layer (HIT)” solar cells have gained popularity after it was demonstrated by Sanyo that they can achieve stable conversion efficiencies, as high as crystalline silicon (c-Si) cells, but where the cost may be reduced with the help of amorphous silicon (a-Si:H) low temperature deposition technology. In this article, we study N-a-Si:H∕P-c-Si front HIT structures, where light enters through the N-a-Si:H layer. The aim is to examine ways of improving the open-circuit voltage, using computer modeling in conjunction with experiments. We also assess under which conditions such improvements in Voc actually occur. Modeling indicates that for a density of states Nss⩾1013cm−2 on the surface of the P-c-Si wafer facing the emitter layer, Voc is entirely limited by this parameter and is lower than 0.5V. We also learn that it is possible to increase the Voc to ∼0.73V by reducing this defect density to ∼1010cm−2, by reducing the surface recombination speed of the electrons at the back P-c-Si∕aluminum contact (SnL), and by improving the lifetime of the carriers (τ) in the P-c-Si wafer to ∼5ms. Modeling further indicates that when τ⩽0.1ms, the sensitivity of Voc to SnL vanishes, as very few back-diffusing electrons can reach the back contact. Improvements in Voc by decreasing both the defect density on the surface of the P-c-Si wafer facing the emitter layer and SnL have been achieved in practice by (a) improved passivation thanks to a thin intrinsic polymorphous silicon layer deposited on the c-Si wafer (instead of a-Si:H) and (b) using localized aluminum and back surface field layers to attain a lower SnL. Experimentally, a Voc of 0.675V has already been attained. Simulations indicate that the lifetime of carriers inside the P-c-Si wafer of these cells is ∼366μs and needs to be improved to achieve a higher Voc.

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In this paper, we show how we developed a visualisation tool to challenge perceived notions about biosecurity on poultry farms. Veterinarians and veterinary public health professionals tend to present biosecurity measures as a universal and cost-effective solution for preventing and controlling diseases on farms. However, we illustrate how biosecurity is an ill-defined term, making it difficult to talk about or apply in practice. As a result, we demonstrate how we moved away from using the term biosecurity in our research by designing a visualisation tool. The tool was to allow us to open up dialogue around disease prevention and control, and make tangible the tacit situated practices of stakeholders working along the poultry supply chain. Our findings show that for those working along the poultry supply chain, the term biosecurity was either consistently open to interpretation, or too rigid to reflect or allow for local variations. We conclude by highlighting how our visualisation tool offers insights into why researchers must move beyond using biosecurity as a term, and instead envisage, design, and develop local solutions to prevent and control diseases on poultry farms.