Efficiency of solar cells

Muffler, H-J. Bar, M. Lauermann, I. Rahne, K. Schroder, M. Lux-Steiner, M. C. Fischer, C.-H. Niesen, T. P. Karg, F. 2006. Colloid attachment by ILGAR-layers Creating fluorescing layers to increase quantum efficiency of solar cells. Sol. Energy Mater. Sol. Cells 90 3143-3150. 

In retrospect, we also explain as being due to the formation of n-n+ junctions the improvement in the conversion efficiency of solar cells made with hot-pressed, polycrystalline n-CdSe upon diffusion of cadmium metal, and n-type dopant, into the boundaries.43... 

Two observations can be made based on this simple calculation. If one examines Figure 9.7, one readily observes that resources such as coal, oil, and gas can last in the decades to century range, whereas nuclear options can last far longer. Second, solar energy seems to provide about 5000 TW of solar radiation that gets radiated back into space. For argument s sake, let us assume that the efficiency of solar cells is about 10%, and only 30% of the earth s surface area is land. This means that only 0.1 x 0.3 x 5000 = 150 TW is potentially useful. However, it is inconceivable that all the earth s land area will be utilized for solar energy, so perhaps only 1% can be used. 

This is considerably different from the recombination reaction with, for example, typical ruthenium dyes. This slow re-reduction of the dyad is explained by the low redox potential of the osmium center, the value of 0.66 V (vs. SCE) observed, points to a small driving force for the redox process. This observation is important for the design of dyes for solar cell applications. Osmium compounds have very attractive absorption features, which cover a large part of the solar spectrum. However, their much less positive metal-based oxidation potentials will result in a less effective re-reduction of the dyes based on that metal and this will seriously affect the efficiency of solar cells. In addition, for many ruthenium-based dyes, the presence of low energy absorptions, desirable for spectral coverage, is often connected with low metal-based redox potentials. This intrinsically hinders the search for dyes which have a more complete coverage of the solar spectrum. Since electronic and electrochemical properties are very much related, a lowering of the LUMO-HOMO distance also leads to a less positive oxidation potential. 

Building and testing efficiency of solar cells Earth observations and satellite imaging... 

Figure 15.7 Time-courses change under a dry heat test of normalized photoconversion efficiency of solar cells stored at 85° C, with a gelled molten salt electrolyte (solid line), a molten salt electrolyte (long dashed line), a gelled organic solvent electrolyte (short dashed line), and a organic solvent electrolyte (dotted line) [25]. (Reprinted by permission of the Publisher, The Royal Society of Chemistry).

Recently, especially since the LLP phenomenon in SrAl204 Eu, Dy was reported in 1996 [1], LLP materials have been extensively investigated due to its potential application in display in the dark, energy storage, enhancement of the conversion efficiency of solar cell and the fabrication of re-writable three-dimensional optical memory devices, etc [2-5],... 

At present the IV-VI series of semiconducting materials comprises a number of the most promising materials for IR applications [1-4]. An interest in these materials is primarily because they are narrow band gap semiconductors and therefore have the potential to be employed in devices as optically active components in the near-infrared (NIR) and infrared (IR) spectral region and are hence beneficial to applications for solar cells, detectors, telecommunications relays, etc. The interest in the IV-VI materials has also grown in recent years because of the observation that they are thought to demonstrate efficient multiple exciton generation (MEG) [3,5-7]. This has implications for the efficiencies of solar cells and other applications based on these materials, especially as it provides a means by which the Shockley/Queisser efficiency limit may be overcome. 

The relatively low efficiency of solar cells exposed to white light can be circumvented by using LSC as beam splitters and couple them to photovoltaic cells with optimum sensitivities in different spectral ranges, and hence using the solar spectrum in a more efficient fashion. 

Fig. 7 Theoretically calculated conversion efficiency of solar cell materials versus band gap for single junction cells (after Adolf Coetzberger, Christopher Hebling, Sol. Energy...

UC of sub-band gap photons for a conventional single-junction bifacial solar cell was presented by Trupke et al. in 2002 [44]. The upconverter, consisting of Er " -doped NaYp4, was located on the rear side of a bifacial cell, thus leading to a response of the cell when it was excited at 1500 nm. From then on, significant improvement, including both theoretical analysis and experimental achievements, has been reported in the field of solar UC. According to the literatures, UC is predicted to enhance the efficiency of solar cells when mounted on the rear of the solar cell [45, 46]. 

Figure 41 (a) A comparison between the structures and efficiencies of solar cells comprising PyF versus reference PCBM (b) EQE... 

---