Storm doors are typically single pane glass so low-e glazing is out of the question. You might look into an applied glass tint, a newly constructed porch or a large tree etc.???

Storm doors are designed to be removed in the summer months.

Although they do make 1/1 insulated glass panels for storms doors, your door is still going to cook.
Did you ever put your arm down on your car in the sun? Hot!
I believe your only solution is to replace the inside 1 3/4" steel door with a fir wood door. It won't get hot.

The Porch Guy

Here is a link that might be useful: My Album

What color is your inner door painted, if it is a dark color that will be a good part of the problem. Try a light color and see if this helps. Most door manufacturers will tell you not to paint a steel door a dark color if it is exposed to a lot of sunlite especially if you use a storm door