therefore, if the manufacturers switch to OVPD technology they will need to pay only for materials?
No. Their contract is based on a certain fee ......
https://www.oled-info.com/...terials-and-technology-supply-agreements
UDC did not disclose the financial terms of these new agreements, but we do know that Samsung will pay a license fee throughout the agreement period.
....and it does not matter whether OPVD or VTE is used to apply the material
Regards
baggo-mh