If radiator temperature is critical you can just run a heat pump to boost it. Modern heat pumps can get pretty close to the Carnot limit for the temperature interval, for example a pump cooling to 300K and dumping out heat at 400K (125°C) will have a theoretical COP limit of 4 and a practical limit of 2.5-3.

That means that for every 3 units of heat your chips emit, you will use a 4th unit to spin the pump. If your panels generate 150kW, you will only have 113kW available for compute and the rest is cooling. Radiators will more than halve vs 340K operation, so it's net beneficial.

It's all a giant techno-economic optimization problem: the extra mass of solar panels you need vs saved radiators vs mass of the pump, the die temperatures you achieve and corresponding performance, durability and chip price point etc.