Trying to prepare for the upcoming summer – has anyone found good curtains/blinds for blocking out heat?

We currently have lighter-colored curtains that let in a good amount of light. On the hottest days of the summer last year, our brand-new AC system couldn't get our small 2-bedroom house below 78 degrees. We have since gotten new insulation, but I'm wondering if getting darker curtains could help as well. Anyone have any recommendations?