There is no evidence that PDE5 inhibitors damage sperm. They may allow you to successfully have intercourse, which can help you and your partner conceive if that was what was causing the problem.
However, if there is another reason for difficulty conceiving, the medication will neither help your chances nor hurt them.
This information is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your healthcare provider.