Troubleshooting TempDB for Performance Bottlenecks
Tempdb is used to hold:

Temporary user objects that are explicitly created, such as: global or local temporary tables and indexes, temporary stored procedures, table variables, Tables returned in table-valued functions, or cursors.To capture sessions which are causing tempdb allocation ,try to use sp_blitz or refer this article more insight into tempdb. https://www.mssqltips.com/sqlservertip/4356/track-sql-server-tempdb-space-usage/