Organic/Inorganic Hybrids for Solar Energy Generation
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sor source in the polymer matrix.28,29 To date, even with improved architecture, hybrid solar cell efficiencies remain well below those achieved in the pure organic systems. Hence, interfacial studies of structural, chemical, and electronic properties in the polymer/metal oxide systems are critical in advancing this field. As an introduction to hybrid solar cells, we first consider simple bilayer architectures as shown in Figure 1: (a) a crosssectional schematic and (b) a cross-sectional transmission electron microscopy image of a P3HT/ZnO bilayer solar cell. In hybrid photovoltaic devices, light absorption occurs in the conjugated polymer, resulting in bound electron-hole pairs (excitons). The excitons then dissociate to
Hybrids for Solar Energy Generation Julia W.P. Hsu and Matthew T. Lloyd
Abstract Organic and hybrid (organic/inorganic) solar cells are an attractive alternative to traditional silicon-based photovoltaics due to low-temperature, solution-based processing and the potential for rapid, easily scalable manufacturing. Using oxide semiconductors, instead of fullerenes, as the electron acceptor and transporter in hybrid solar cells has the added advantages of better environmental stability, higher electron mobility, and the ability to engineer interfacial band offsets and hence the photovoltage. Further improvements to this structure can be made by using metal oxide nanostructures to increase heterojunction areas, similar to bulk heterojunction organic photovoltaics. However, compared to all-organic solar cells, these hybrid devices produce far lower photocurrent, making improvement of the photocurrent the highest priority. This points to a less than optimized polymer/metal oxide interface for carrier separation. In this article, we summarize recent work on examining the polymer structure, electron transfer, and recombination at the polythiophene-ZnO interface in hybrid solar cells. Additionally, the impact of chemical modification at the donor-acceptor interface on the device characteristics is reviewed.
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TCO Glass
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Organic photovoltaics (OPVs) are targeted in small electronics, portable power, and integrated building applications because they are light weight, mechanically flexible, available in different colors, and compatible with roll-to-roll printing technologies for inexpensive manufacturing.1,2 Most common OPVs consist of conjugated polymers as absorbing and donor materials (e.g., poly[3-hexylthiophene], P3HT) and fullerene derivatives (e.g., [6,6]-phenyl-C61-butyric acid methyl ester, PCBM) as acceptor materials. Presently, this materials system is capable of producing power conversion efficiencies (for areas ≥ 1 cm2) of 4.4–5.0%.3–5 By employing lower bandgap donor materials and utilizing a C70 derivative as an acceptor, certified power conversion efficiencies above 7.4% for a small area sample (∼0.1 cm2) have been achieved.6 Increased power conversion efficiency and device stability are the two most critical issues for OPVs to fully realize their technologica
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