Commercially available solar panels now routinely convert 20% of the energy contained in sunlight into electricity, a truly remarkable feat of science and engineering, considering that it is theoretically impossible for silicon-based solar cells to be more than 32% efficient. This upper bound, known as the Shockley-Queisser Limit, was first calculated by the eponymous scientists (who actually gave 30% as their original limit) in the Journal of Applied Physics in 1961  (see also updates by Rühle ).
Now, if we can answer why solar panels are thus limited, we can understand the essentials of photovoltaics (PV), which have their basis in the photoelectric effect, and p-n semiconductor junctions. While many have never heard of it, the photoelectric effect is of monumental importance, and when Albert Einstein received the 1921 Nobel Prize in physics, it was “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect,” while p-n junctions lie at the foundations of modern electronics, including transistors and LEDs. Indeed, a solar cell is essentially an LED in reverse: Instead of an electric current generating light, light generates electric current!
Whether 100 or 100,000, it’s consuming the fossil fuels extracted by these companies that ultimately drives climate change
The famous 71% figure comes from tracing fossil fuels to the companies that extracted the raw fuel, ignoring all the downstream companies, governments, and individuals that actually use these fuels
Viewed from the perspective of fossil fuel consumption, global warming emissions are generated by myriad actors, with households the final common driver of the overwhelming majority of climate altering emissions
Transitioning away from fossil fuels requires a revolution in how economies and households use energy, and it is largely irrelevant that 100 companies extract the majority of fossil fuels
The 100 companies/71% figure is mainly used to discourage meaningful change, and thus acts as a kind of zombie statistic: Relatively small changes in household consumption across the US populace could dramatically reduce warming emissions
A mere 100 hundred companies have generated 71% of warming emissions (based on ), so the refrain goes, and so changing your own habits and thinking this a meaningful response to climate change is either delusion, virtue signaling, the result of corporate propaganda, or some combination thereof. This has become the “zombie statistic” of popular climate discourse, cited almost exclusively by those that do genuinely care about the ongoing climate catastrophe, and yet ironically employed toward the utterly counterproductive ends of paralysis and inaction. While not untrue (and indeed an important element of a full understanding of climate change), the zombie nature of this factoid arises from the nihilistic implications that are typically assumed.