Material Properties Flashcards
7 cards from real SE ENGR. practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Material Properties flashcards as text
Why does gallium arsenide (GaAs) reach higher single-junction efficiency than silicon?
Answer: Its direct bandgap of about 1.42 eV is near the single-junction optimum
GaAs's direct 1.42 eV bandgap sits near the Shockley-Queisser optimum and absorbs strongly.
Light-induced degradation (LID) in p-type boron-doped Cz silicon is mainly caused by:
Answer: Boron-oxygen defect complexes forming under illumination
Boron-oxygen complexes form during the first sunlight exposure and reduce minority carrier lifetime.
Why does a typical crystalline silicon cell use a silicon nitride (SiNx) coating?
Answer: For anti-reflection and surface passivation
A SiNx layer about 75 nm thick cuts reflection and its hydrogen passivates surface and bulk defects.
Why does acetic acid form in aged EVA-encapsulated modules?
Answer: Hydrolysis of the vinyl acetate groups when moisture is present
Moisture and heat hydrolyze vinyl acetate into acetic acid, which corrodes the metallization.
Tempered (toughened) glass is used on module fronts because it:
Answer: Has higher strength and breaks into small blunt pieces
Tempering puts the surface in compression, giving 3–5 times the strength of annealed glass and safe breakage.
What does a module's power temperature coefficient of -0.35%/°C mean?
Answer: Power falls 0.35% for each °C of cell temperature above 25 °C
Pmax falls linearly by 0.35% of its STC rating for each degree the cell is above 25 °C.
Using the coefficient of -0.35%/°C, about how much power does a 400 W module lose at a 65 °C cell temperature?
Answer: 56 W
(65−25) × 0.35% = 14%, and 14% of 400 W is 56 W.