Solar cells thermal systems

A high optical transparency is a basic requirement for optical applications. However, conventional polyimides such as PMDA/ODA have a low optical transparency owing to their dark yellow coloration (they are semitransparent, not opaque). Colorless polyimides have been developed for use in space components, such as solar cells and thermal control systems for the first time. ... 

Fig. 5.37. (a) I/V characteristics of typical MDMO-PPV/PCBM solar cells with a LiF/A1 electrode of various LiF thicknesses ( 3 A, 6 A, 12 A) compared to the performance of a MDMO-PPV/PCBM solar cell with a pristine A1 electrode ( ). (b) and (c) are box plots with the statistics of the FF and Voc from 6 separate solar cells. LiF or SiOx were thermally deposited at a rate of 1-2 A/min from a tungsten boat in a vacuum system with a base pressure of 10-4 Pa. We emphasize that, for thickness values of the order of 1 nm, LiF/SiOx does not form a continuous, fully covering layer, but instead consists of island clusters on the surface of the photoactive layer. Slow evaporation conditions are essential for more homogenous distribution of the LiF on the organic surface. The nominal thickness values given here represent an average value across the surface of the substrate. The metal electrode (either aluminum or gold) was thermally deposited with a thickness of 80 nm... 

In evaporation-intercalation devices solar energy conversion would, at least in the more efficient case of a thermal system, not be converted by exciting electrons and rapidly separating them from holes, but by transferring atoms or molecules across a phase boundary by evaporation which is usually a very efficient process. It is, consequently, neither necessary to use materials which are well crystallized like those developed for photovoltaic cells nor is it necessary to prepare sophisticated junctions. A compacted polycrystalline sheet of a two-dimensional material which is on one side placed in contact with an electrolyte, sandwiched between the layer-type electrode and a porous counter electrode, as it is used in fuel cells, would constitute the central energy conversion unit. Some care would have to be taken to choose an electrolyte which is suitable for intercalation reactions and which is not easily evaporated through leaks in the electrodes. Thin layers of polymeric or solid electrolytes would seem to be promising. 

Besides PV cells, solar radiation can also be used in concentrating solar thermal systems or for the photo-electrochemical decomposition of water. Concentrating solar systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated light... 

Same-metal oxides of materials are not normally used in MOS devices, due to their heterogeneity and nonstoichiometry (chemical composition depends significantly on the conditions of both production and snbsequent thermal treatment [49-51]). Therefore, at present, preference is given to MOS structures containing silicon oxides. Examples of such systems include Si02 on substrates made of GaAs, InP, and InSb, which were studied by IR absorption [52-54]. Nevertheless, MOS structures with same-metal oxides A B are still considered to be promising for a number of applications in optoelectronics, such as solar cells [1]. 

---