This was my senior team project in engineering school, in 1974. Here were our findings:
The power needed to run a small absorption refrigerator can be supplied by a solar collector of about 32 square feet, but the temperature required to boil the ammonia out of the water requires a concentrating collector (not a flat plate)- and hence requires an aiming mechanism for the optics.
Next, since the sun don't shine in the night time, you need some means of storing the cold overnight until the sun comes up again. Water frozen into ice is the cheapest solution, so the reefer makes ice while the sun shines and stays cold overnight on that ice.
But now you have to manage the melt water- catch it as it melts and return it to the ice maker in preparation for the next day's ice making.
By the way, since the energy required to run the reefer costs nothing, you can afford to compromise on the coefficients of performance and still have a viable operating model for the device. This is why ammonia absorption air conditioning is commonly used as a topping cycle on the outlet stream of a big boiler operation where there's lots of waste heat on hand.