Solar interface research, surface

The cost-effective deployment of large areas of solar collectors will most probably be polycrystalline materials, with all index planes emerging at the surface. Therefore, it is not expected that the structural determination of solar materials surfaces will be applied except for a few special cases. However, determining S/S inter facial structures is important, as shown by Figs. 6-9 in Ref. 2. The challenge in solar interface research will be to understand the changes in surface activity of heterogeneous real surfaces and interfaces. Here, SEM and possibly STEM techniques should be used extensively. 

Table 1 of a paper by Murr (2) lists problems and/or concerns related to specific interface materials and specific components of SECS. In Table 2 of the same work, he related topical study areas and/or research problems to S/S, S/L, S/G, L/L, and L/G interfaces. It is also useful to divide interface science into specific topical areas of study and consider how these will apply to interfaces in solar materials. These study areas are thin films grain, phase, and interfacial boundaries oxidation and corrosion adhesion semiconductors surface processes, chemisorption, and catalysis abrasion and erosion photon-assisted surface reactions and photoelectrochemistry and interface characterization methods. The actual or potential solar applications, research issues and/or concerns, and needs and opportunities are presented in the proceedings of a recent Workshop (4) and summarized in a recent review (3). 

Surface chemistry, in general, is an area in which the ability to selectively modify the chemical and physical properties of an interface is highly desirable. The synthetic chemistry of surfaces is now in a developing stage, particularly with respect to the attachment of electroactive redox sites to metal or semiconductor surfaces (L-3). Single component and bilayer (4) electroactive films have been a field of intense research activity since their applications are apparent in catalysis, solar energy conversion, directed charge transfer, electrochromic devices, and trace analysis. 

Around 1975, investigations of photoelectrochemical reactions at semiconductor electrodes were begun in many research groups, with respect to their application in solar energy conversion systems (for details see Chapter 11). In this context, various scientists have also studied the problem of catalysing redox reactions, for instance, in order to reduce surface recombination and corrosion processes. Mostly noble metals, such as Pt, Pd, Ru and Rh, or metal oxides (RUO2) have been deposited as possible catalysts on the semiconductor surface. This technique has been particularly applied in the case of suspensions or colloidal solutions of semiconductor particles [101]. However, it is rather difficult to prove a real catalytic property, because a deposition of a metal layer leads usually to the formation of a rectifying Schottky junction at the metal-semiconductor interface (compare with Chapter 2), as will be discussed below in more... 

Adhesion is a more difficult problem. There are many chemically different interfaces in a laminant stack glass-EVA, EVA-solar cell surface (oxidized silicon or some anti reflection (AR) coating), cell back surface metallization-EVA, EVA-back sheet, and EVA-bus bars (copper or tinned copper). Each of these interfaces is important, because mechanically good adhesive bonds will often fail by delamination after exposure to humidity in the field. Water vapor will permeate through polymers and, if there is a non-chemically bonded surface, water may collect and cause failure by displacement. Tables I, II, and III provide details of some of the research efforts in adhesion. 

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