However, there is another side to the solar energy story that is becoming increasingly important. As millions of solar panels grow older, scientists are asking a simple but critical question: What should happen when these panels stop working? Experts estimate that by 2050, the world could generate more than 80 million metric tons of discarded solar panels. Thin-film solar panels also contain valuable metals that often require harsh chemical treatments to recover. This approach could help make solar energy cleaner, more sustainable and truly circular for generations to come.