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Solar Cells Based on Diblock Copolymers: A PPV Donor Block and a Fullerene Derivatized Acceptor Block
Published in Sun Sam-Shajing, Sariciftci Niyazi Serdar, Organic Photovoltaics, 2017
Rachel A. Segalman, Cyril Brochon, Georges Hadziioannou*
The attractiveness of polymeric materials to make low cost, lightweight, flexible solar cells is now obvious and the potential of low molecular weight organic semiconductors to reach high power conversion efficiencies has been demonstrated by processing materials with high purity in terms of contaminants and structure. The records in power conversion efficiency, however, were achieved by optimizing the structure of donor and acceptor homopolymers blends by trial and error in casting of the films [49]. There is undeniable potential in optimizing and controlling the nanostructure of the active layer in a more systematic manner. Nanometer-scale structuring via the microstructuring of liquid crystalline materials has also led to some of the best reported photovoltaic quantum efficiencies, 34% at 490 nm [50]. In terms of processing efficiency and elegance, however, nanostructuring can easily be done by taking advantage of the self-assembling nature of polymers. The ability of block copolymer to be chemically tuned to microphase separate on the proper scale and into the proper structure so as to possess the desired chemical, physical, and electronic properties to optimize the overall device is in our opinion an untapped potential.
Certification and Characterization of Photovoltaic Packaging
Published in Michelle Poliskie, Solar Module Packaging, 2016
A PV cell is the smallest subassembly capable of producing power. The active layer is composed of a semiconductor film responsible for converting light into electricity. This phenomenon is called the photoelectric effect, and it gives this branch of solar energy its name. For simplicity, p-n–type semiconductors, such as single crystalline silicon, will be used as an example. Incident light with energy equal to or greater than that of the semiconductor’s band gap (Eg) will knock electrons out of their atomic orbitals and into the n-type semiconductor layer, also known as the electron donor. This leaves behind a hole in the p-type semiconductor layer, also termed the electron acceptor (Figure 2.1). The band gap is an inherent characteristic of the semiconductor material, and it makes each chemistry sensitive to specific wavelengths of light. The intermediate zone where these two layers meet is called the p-n junction layer. The separation of charges creates a measurable voltage. Connecting the grid metallization and metallic backsheet through the interconnects allows for the flow of electrons out of the n-type layer and to the p-type layer. The flow of electrons through the circuit results in a measurable current. The voltage multiplied by the current will define the solar cell’s power, and a few milliwatts (mW) is typical.
Electroluminescence: an introduction
Published in D R Vij, Handbook of Electroluminescent Materials, 2004
D Haranath, Virendra Shanker, D R Vij
High-field EL consists of excitation of luminescence centres by majority charge carriers accelerated under the action of strong electric (a.c. or d.c.) fields ~106V/cm. This type of EL mechanism relies on inter- and intraquantum shell transitions at luminescent centres/ions. High-energy electrons raise the luminescent centres to the excited quantum states via impact ionization and/or impact excitation. The excited centres must eventually relax to ground state emitting photons, known as the radiative relaxation process. The electron excitation and radiative relaxation are atomic transitions localized at the luminescent centre. The active layer can consist of a doped semiconductor of II–VI compounds and, in addition, either a powder (embedded in a matrix) or an organic or inorganic thin film.
Evaluation and spatio-temporal analysis of surface energy flux in permafrost regions over the Qinghai-Tibet Plateau and Arctic using CMIP6 models
Published in International Journal of Digital Earth, 2022
Junjie Ma, Ren Li, Zhongwei Huang, Tonghua Wu, Xiaodong Wu, Lin Zhao, Hongchao Liu, Guojie Hu, Yao Xiao, Yizhen Du, Shuhua Yang, Wenhao Liu, Yongliang Jiao, Shenning Wang
The active layer in permafrost regions is the link between the atmosphere and the land surface. It has an important impact on the energy-water exchange between the land surface and the atmosphere (Li et al. 2012; Zhao et al. 2000). The freeze–thaw process of the active layer is highly complex. It encompasses physical and chemical changes that have significant impacts on surface energy fluxes (Hu et al. 2019; Luo et al. 2014; Wani et al. 2021). Previous studies have confirmed that the freeze–thaw process can significantly affect hydrothermal systems in permafrost regions, especially the surface energy flux within the land surface (Eugster et al. 2000). Moreover, the freezing and thawing of soil moisture require the release and absorption of large amounts of latent heat (Zhao et al. 2000). Furthermore, the energy partitioning at the surface also buffers against soil temperature change attenuating its magnitude (Eugster et al. 2000).
Load transfer of pile foundations in frozen and unfrozen soft clay
Published in International Journal of Geotechnical Engineering, 2020
Abdulghader A. Aldaeef, Mohammad T. Rayhani
Frozen ground may fail to maintain its frozen condition in confrontation of global warming. In warm permafrost, a small temperature increase may be sufficient to cause extensive thawing. In cold permafrost, temperature increase by couple of degrees may result in significant increase in active layer depth (annual thaw depth), which can promote significant thaw settlement and increase the potential frost heave upon freezing. The thaw settlement in ice-rich soils could be more disruptive and cause inclusive damage to the structures (Esch and Osterkamp 1990). Temperature record in high-latitude regions of earth has shown 0.6°C increase per decade over the last 30 years, which represent twice the global average (IPCC 2013). This normally would result in thawing the frozen ground and reduce the frozen depth (Brown and Romanovsky 2008). Lawrence and Slater (2005) used weather data to model permafrost area in the Northern Hemisphere under global warming impact predicting present-day permafrost as well as permafrost condition over the 21st century. The model showed that a reduction in near surface permafrost area from 12 to 10.5 million of Km2 has occurred between 1900 and 2000. Dramatic permafrost degradation was predicted by 2100 yielding 1 million km2 of near surface permafrost area.
Estimating methane emissions using vegetation mapping in the taiga–tundra boundary of a north-eastern Siberian lowland
Published in Tellus B: Chemical and Physical Meteorology, 2019
T. Morozumi, R. Shingubara, R. Suzuki, H. Kobayashi, S. Tei, S. Takano, R. Fan, M. Liang, T. C. Maximov, A. Sugimoto
We defined a 50-m monitoring transect, which was composed of a 100 × 50 m survey plot at site K (Fig. 2a) with local survey points distributed throughout a 10 × 10 km area of the Indigirka lowland (Fig. 1). At site K, the relative elevation from the lowest base level was measured using a surveying telescope (AT-B4, TOPCON, Tokyo, Japan) at every 2.5 m point along a 50 m transect on 31 July 2012, and in 5 m grids at 231 points over the 100 × 50 m survey plot on 14 July 2013. In addition, we measured seasonal thaw depth (i.e. active layer depth) using a metal rod, and estimated frost table height by subtracting the thaw depth from the relative elevation over the same survey plot. Volumetric soil moisture was also measured using a portable moisture sensor (Trime-Como, IMKO, Ettlingen, Germany) between the surface and a depth of 8 cm, by performing four observations at every 5 m points along the monitoring transect at site K in mid July 2012, 2014 and 2015, as well as at 70 local survey points distributed throughout the 10 × 10 km area in the Indigirka lowland in mid July 2014.