No. Level 20 is the highest level.
As you said: 20 is the highest level described in the PHB, and XP gains beyond 355,000 are described in DMG Chapter 7 as gaining one other advancements, not levels. There is no WotC "Tier of Play" beyond level 20.
However, you're not alone in looking for higher-level play options. There's nothing stopping you and your table from designing the progression you'd envision from higher levels and you'd be joining a long history of those who have done so1 Just understand that you're intentionally moving away from the design principles2 of 5e when doing so.
1 - See Skip Williams' High-Level Campaigns for 2e, for example; in my experience 2e's been a pretty good go-to for supplementing 5e. Examples here: , , .
2- "The basic premise behind the bounded accuracy system is simple: we make no assumptions on the DM’s side of the game that the player’s attack and spell accuracy, or their defenses, increase as a result of gaining levels. Instead, we represent the difference in characters of various levels primarily through their hit points, the amount of damage they deal, and the various new abilities they have gained. Characters can fight tougher monsters not because they can finally hit them, but because their damage is sufficient to take a significant chunk out of the monster’s hit points; likewise, the character can now stand up to a few hits from that monster without being killed easily, thanks to the character’s increased hit points. Furthermore, gaining levels grants the characters new capabilities, which go much farther toward making your character feel different than simple numerical increases." Rodney Thompson, Legends and Lore, quoted in "Under the Hood--Bounded Accuracy" at roleplayeschronicle.com. Wizards.com has apparently lost many recent L&L articles, and any references to them seem to be broken links.