You can use a solar panel to charge some laptops without a battery bank, if the solar panel comes with a buck/boost converter to match the DC input on your laptop.
As an example, if your laptop charges from USB-C conforming to the PD (Power Delivery) standard, you could use something similar to this nominal 100W solar panel.
https://www.amazon.com/Portable-Foldable-Charger-Camping-Stations/dp/B0C69LNKSP
It has four separate charging outputs from the small rectangular buck/boost converter box on the back of the solar panel (see photo below).
【4 Output Ports For Different Usage】The foldable solar panel designed with 4 output ports of different types:
1) DC output ( 12-18V, 5.5A Max),
2) USB C PD ( 5V/3A, 9V/3A, 12V/3A, 15V/3A),
3) Two USB QC3.0 outputs will quickly charge your phone, laptop, tablets, iPad, GPS, USB fan, camera or other devices.
If (and it's a big if) your laptop can auto-negotiate with the solar panel converter at USB-C 15V 3A, you can charge the laptop at 45W.
This is well down on the claimed maximum 100W output of the panel, but the manufacturers probably designed it to power more than one device simultaneously and assumed you'll use other outputs to charge phones, tablets, etc.
45W should be enough to charge the battery (slowly) when the laptop is switched off, but only when the sun shines.
A better solution would be a larger solar panel with a 20v 5A USB-C output (100W) if your laptop supports USB-C PD charging.
https://www.trustedreviews.com/explainer/what-is-usb-pd-4368197
If your laptop doesn't have a compatible USB-C PD charging input, you'll probably have to fall back on the DC-to-AC mains inverter concept and your laptop's mains charger, with all the problems already discussed of matching the charger to the inverter, to avoid overloading.
Double conversion wastes energy converting the solar panel's variable DC voltage into AC mains, then converting AC mains back to a DC voltage to charge the laptop. Not very efficient.
The two USB QC 3.0 (Quick Charge) outputs on this panel probably won't be suitable for your laptop.
https://en.wikipedia.org/wiki/Quick_Charge
A more professional approach which I've used at work is to add another pulley for a second alternator in the engine bay (usually 24V) and a pair of large 100Ahr batteries to run a 1kVA AC inverter. Obviously this is not practical in a small family runabout, but might be possible in a large Jeep, RV or pickup truck. It's not a cheap solution either.