Spiny Norman said:
Perovskites are a class of materials that have a cube-like and diamond-like crystal structure. Though the first perovskites were discovered more than 180 years ago, they were only applied to solar cells within the last two decades. They work the same way other semiconductor based cells do; light from the sun excites electrons in the material, and those electrons flow to conducting electrodes and generate a current.
In 2006, perovskite cells were about 3% efficient. Fast forward to 2020, and some researchers were boasting 25% efficiency. For comparison, the first silicon solar cells were created in a lab as far back as 1940. In the 80 years since then, they’ve matured steadily to the point where they are now typically 15-20% efficient.
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My knee-jerk reaction is “which perovskite?”
https://en.wikipedia.org/wiki/Perovskite_(structure)
“Perovskite structures are adopted by many oxides that have the chemical formula ABO3”
Ah, I see. “ perovskite solar cells, which contain methylammonium lead halide” were first discovered in 2009.
“Methylammonium lead halides (MALHs) are solid compounds with perovskite structure and a chemical formula of CH3NH3PbX3, where X = I, Br or Cl. They have potential applications in solar cells”.
These minerals photo-dissociate, they break down under the influence of light and heat, which doesn’t seem the best strategy for a solar cell.
https://en.wikipedia.org/wiki/Perovskite_solar_cell
“The most commonly studied perovskite absorber is methylammonium lead trihalide (CH3NH3PbX3, where X is a halogen ion such as iodide, bromide or chloride), with an optical bandgap between ~1.55 and 2.3 eV depending on halide content. Formamidinium lead trihalide (H2NCHNH2PbX3) has also shown promise, with bandgaps between 1.48 and 2.2 eV.”
Solar cell efficiency is limited by the Shockley-Queisser limit, where there is a balance between energy uptake and the energy loss by radiative recombination, based on the standard solar spectrum. The maximum power conversion efficiency is correlated to a respective bandgap, forming a parabolic relationship. “The most efficient bandgap is found to be at 1.34 eV, with a theoretical maximum power conversion efficiency (PCE) of 33.7%”.
Silicon has a band gap of 1.1 eV, too small for theoretical maximum efficiency.
Germanium has a band gap on 0.67 eV.
Other attempts are being made to get close to the optimal band gap. The band gaps of Cu2ZnSnS4 and Cu2ZnSnSe4 are 1.5 and 1.0 eV..