Conventional solar cells also suffer from decreased efficiency (-0.45%/°C) as temperature increases, a the inclusion of TEGs could help dissipate this waste heat while simultaneously increasing solar panel efficiency.
Minor correction/note: most modern modules/cells have a temperature coefficient in the range of approx. -0.27 to -0.35%/°C. A little better than -0.45%.
See fig 14 in [1] for data through 2021/22, and then the more recent transition to n-type cells is helping more [2]. This database [3] doesn't list module release date, but filtering for modules with STC rating over 500 W (decent proxy for "modern") gives an average of -0.34%°C, with a lot at or better than -0.30.
I've done some research on exactly this, and the efficiencies of TEGs makes this a tough prospect. It started to work out in our favor when using concentrated solar to reduce the amount of paneling needed, but that's no longer an economic driver, and you get a much better return on investment by skipping the TEGs and just plopping a few extra panels down in a lake. You can also flip the configuration and use TEGs to generate power from the solar heating, but the terrible efficiency bites us again and you're better off buying more panels instead.
TEGs will concentrate heat. A TEG adds significant thermal resistance to your system. For a TEG to produce meaningful energy, you'd almost certainly need a heat sink of some sort. From a total system efficiency and cost perspective, you'd probably be better off just directly mounting a heat sink to the back of a panel.
In the domestic/commerical, the simplest solution to this is to add more solar to compensate for the drop in efficiency. The next cheapest approach would be to cool the panels by heating water for domestic/industrial use, although the economics aren't as straightforward (depends on the cost of hearting fuel being displaced).
> although the economics aren't as straightforward
And you're multiplying the points of failure and complexity of the system. That's the beauty of solar panel imho, not much an go wrong, adding water, potentially boiling water that is, pipes, pumps, &c. sounds like an headache
