Material Properties Flashcards

Why are perovskite absorbers such as MAPbI₃ hard to use commercially?

Answer: Poor stability under moisture, heat and UV

Halide perovskites break down quickly when exposed to moisture, oxygen, heat and light unless well encapsulated.

Which heat transfer fluid property matters most for freeze protection in a solar thermal loop?

Answer: Low freezing point, for example from propylene glycol mixtures

Glycol-water mixtures lower the freezing point so collectors and piping do not burst in cold weather.

Why is anodized aluminum common for module frames?

Answer: It has a good strength-to-weight ratio and an oxide layer that resists corrosion

Anodizing thickens the protective Al₂O₃ layer, and aluminum keeps frames light yet stiff.

Why is the anodized surface often pierced with grounding washers (WEEBs) on module frames?

Answer: Because the anodized oxide layer is electrically insulating

Anodizing creates a non-conductive oxide, so teeth must cut through it for a reliable equipment ground bond.

Compared with monocrystalline silicon, multicrystalline silicon cells typically have:

Answer: Lower efficiency because grain boundaries cause recombination

Grain boundaries and defects in multicrystalline silicon shorten carrier lifetime and lower efficiency.

For CIGS (copper indium gallium selenide) thin films, raising the Ga/(In+Ga) ratio:

Answer: Raises the bandgap from about 1.0 eV toward 1.7 eV

Replacing indium with gallium widens the CIGS bandgap, which allows bandgap grading.

What material property does the albedo of a ground surface describe for bifacial PV?

Answer: Fraction of incident solar radiation reflected

Albedo is reflectance; for example fresh snow (~0.8) gives far more rear-side gain than grass (~0.2).