ORGANICSOLAR
Understanding organic potential
Any PV technology hoping to increase market share in a competitive environment knows they must seek to obtain the best outcome from their devices to ensure success. Despite the promise of organic and plastic PV opportunities there has been concern regarding the output of such devices. Xuan-Dung Dang and Thuc-Quyen Nguyen of the Departments of Chemistry & Biochemistry and the Centre for Polymers and Organic Solids at the University of California in Santa Barbara discuss photoconductive atomic force microscopy for understanding nanostructures and device physics of organic solar cells.
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lastic solar cells are emerging as alternative energy sources for the future because of their potential for cheap roll-to-roll printing, ease of processing, light-weight and flexibility. However, their current performance is still low for practical applications which partially originate from the poor understanding of device physics and nanoscale morphology of the photoactive layer. Photoconductive atomic force microscopy is a powerful characterization tool to better understand the complex optoelectronic and morphological phenomena of organic solar cells at the nanoscale.
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Inorganic and Organic Photovoltaics Conversion of the Sun’s usable solar energy reaching the surface of the Earth in a single hour into electricity could meet all global energy needs for an entire year. With their potential for low cost, light-weight, flexibility, and ease of processing and installation, plastic solar cells are expected to be the next energy generation technology for the future.
The first solar cells based on organic semiconductors demonstrated by Tang in 1986 had an efficiency of 1.0%. Although research in organic solar cells has only really been active within the past few years, the efficiency has now
reached 7.7%. Scientists have made great efforts on designing new materials to harvest more solar photons and new device architectures to optimize the output power, targeting to achieve an efficiency above 10% in the next few years.
Although, there has been much development and progress in this field, the technology is still far from practical applications. One of the main obstacles to achieve the higher efficiency is that device physics and how the photoactive morphology impacts the device performance are not fully understood.
In conventional inorganic photovoltaics, which consist of two layers of p-doped and n-doped semiconductors, the light absorbing materials
Fig 1: (a) A typical solar cell structure consisting of a PEDOT:PSS deposited onto a glass/ITO substrate. (b) Topographic image obtained using atomic force microscopy showing phase separation where yellow and purple areas are donor and acceptor phases, respectively.
www.solar-pv-management.com Issue VI 2010
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