Digital Object Identifier (DOI) is for the publications; thus you are looking for DOAJ; refer to:

https://doaj.org/application/new

You must use a service offered by a DOI Registration Agency (RA). RAs collect metadata, assign DOI names, and offer other services such as reference linking or metadata lookup. See the list of RAs, and contact the ones whose services best meet your needs. If you do not see an appropriate application listed, consider approaching an existing RA or developing a community to build the service you require (see the DOI Handbook, 8 Registration Agencies, for more information).

The cost of registering new DOI names depends on the services you purchase. Contact a DOI Registration Agency to discuss your options. Each RA is different, and each is free to offer its own business model. For an example of the costs of a DOI service for publishers, see the Crossref publisher fees.

http://www.doi.org