Lumtec from Taiwan is a well-known source for all types of OLED materials: http://www.lumtec.com.tw/

You will also find some guidance on good OLED stacks from publications

Alternatively, at Sigma-Aldrich Website you can find a tool to design OLED stacks from their materials with perfromance expectations

http://www.sigmaaldrich.com/materials-science/learning-center/oled-efabricator.html

@Tobias Canzler. Thanks for the suggestions.

Carbazole-based materials are ideal host for blue emitters. Do you have a deep blue emitter? If yes, then you have to carefully choose the host!

@ Justin Thomas K R. Thanks for the suggestions.

Blue emitters having emission in the rangae 455-470 nm in thin film form

@Hidayath Ulla

Depending on the energy levels you may choose one of the following as host:

CBP, TCTA, SimCP2 or Spri-2CBP

@ Justin Thomas K R. T. Thanks for your suggestions

I am trying with CBP

mCB is also good for this purpose.

@ Justin Thomas. Thanks for the suggestion.