I tried reading the paper. Seems relevant. if changes to manufacturing processes can eliminate the problem then you get a 10% improvement in power output.

isn't panel efficiency important for end-user-installed panels, rather than large power producers' installations? E.g. home use, or factories.

Euros per installed Watt is the important metric. It has been dominated by installation cost (not panel cost) for a while now.

It's one metric, not the only one. Im my residential installation, I was constrained by roof surface. Given certain subsidies, it would have made economic sense for me to pay more per watt if that had meant I could have produced more overall (up to a point, of course).

Using an example of current generation silicon cells, it certainly makes sense not to buy a lot of old technology polycrystalline 72 cell panels with a 300W rating, if you can buy mono si 72 cell 365-370W rated panels instead. There is only so much space on a house roof for a dozen or two dozen, 2.0 x 1.0 meter size panels.

But beyond "top grade 156mm mono cells", such as you can get in a new 360W stc rated panel, there is significantly diminished returns in dollars per watt. Yes you can get sunpower 23% efficient panels but they will literally cost twice as much.

Yes if your goal was to be as independent from the grid as possible. My guess is most people putting them on their roof mostly care about minimizing their long term energy expenditure net of costs.

I'm not entirely sure but the paper seems to indicate that the defect has an impact on the maximum life of a panel - fixing that would directly impact installation cost (by spreading it over a longer life time).

Seems to me that the degeredation they discuss here operates on a very short time scale, completed within a few hours. This result is unlikely to matter significantly for lifetime.

My reading was that you lose 2% for the whole life of the panel, until now no one knew why. So, you could do 2% less installation or get 2% more for the investment, if there is a fix for the issue.

You lose 10% of the power output of the solar panel. i.e. solar panels utilize 20% of the solar energy they receive but within hours that drops to 18% for the life of the panel. So yes, it's a 2% absolute drop relative to the solar energy the panel receives, but it's 10% of what the panel was ever able to produce.

Good quality silicon cell pv panels are typically warranted to produce 83% of their original output after 25 years. Degradation is calculated into long term financial figures for really big photovoltaic systems.

You'll see the warranty examples if you look at the PDF datasheets from the top ten manufacturers of 60 and 72 cell panels. Similar for CdTE and other more exotic thin films.

So if we could stop that degradation, or change the profile of it, then the calculations would yield better investment returns?

yes, however, ROI is more greatly affected by lowering the total bill of materials cost for a large PV install, and in particular the $ per W cost (at STC, standard test conditions) rating for each panel. Going from $0.72/watt to $0.46/watt in single pallet quantities of 20 panels was a huge difference.

they also mention the degradation is reversible, by annealing in darkness, at least for experimental purpouses (your solar panel as a integral device may suffer from annealing at the right temperature, and the duration of annealing in darkness is possibly more than 20% of the degradation time, rendering it useless for "fixing" solar panels).

the most important result is that this initial degradation is finally understood, the first step in preventing, now we need to come up with modified designs or manufacturing steps to eliminate the defect.

> Panel efficiency is mostly of interest for space flight

Surely fundamental research is beneficial to all applications. That said, and as you say, price performance is and should be the primary (research) driver.

One of the big recent improvements was to use lasers to anneal foundry quality silicon to bring them up to par to use for PV.

Although to counter that point more of the cost is in the infrastructure to process the electricity.