In case you are relying on the conduction band (CB) of your materials to create the quantum confinement, you should try efficient n-type doping. Doping must be tweaked so that excess electrons fill the valence band and also your first bound state in the CB. Whith this met, at low temps you should be able to supress all intraband transitions.

Thank you sir,

I do not want to suppress intra band transitions, I need to suppress interband transitions.

Can you provide some literature sources to study on effective and uniform doping of colloidal Quantum Dots.

usually intraband transitions are at lower energies than the interband ones.