Why are you filing single? You are allowed to file a Married Joint return with your deceased spouse for the year of death if the 1099-Div is a 2020 form. If would just be income in a joint return.
If your spouse died prior to 2020 then the payer should have been notified of the death and the 1099-DIV should go to the benificuary of the account.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**