Which material could improve silicon-based solar cell efficiency?

• A. Copper
• B. Gallium arsenide
• C. Perovskite
• D. Silicon carbide

Answer: (C)

The idea behind improving silicon-based solar cell efficiency is to add another absorber with a different bandgap so the device can harvest more of the sun’s spectrum. Perovskite is a great match because its bandgap can be tuned to be in a range (around 1.7–1.9 eV) that absorbs visible light well while leaving lower-energy photons for silicon. This makes a two-junction tandem where the top perovskite layer and the bottom silicon layer work together, often producing more voltage and, importantly, more current than silicon alone. Perovskites also absorb strongly with very thin layers and can be processed cheaply, which helps keep costs down while boosting overall efficiency.

Other options don’t fit this role as well. Copper is a metal and doesn’t contribute to light absorption in a useful solar-cell sense. Silicon carbide has a much larger bandgap, which isn’t ideal for a complementary top cell in a tandem with silicon. Gallium arsenide is highly efficient but expensive and less practical for broad, cost-focused improvements to silicon-based cells. Perovskite’s combination of tunable bandgap, strong absorption, and low-cost fabrication makes it the most promising material to enhance silicon-based solar cell efficiency.