SQLCipher's performance for opening a database is deliberately slow. SQLCipher uses key PBKDF2 to perform key derivation (i.e. thousands of SHA1 operations) to defend against brute force and dictionary attacks. Please see http://sqlcipher.net/design for more information.
The best option is to cache the database connection so that it can be used multiple times without having to open and key the database on each screen. If this is possible, opening the database once during startup is the preferred course of action. Subsequent access on the same database handle will not trigger key derivation, so performance will be quite fast.
If this is not possible the other option is to disable or weaken key derivation. This will cause SQLCipher to use fewer rounds of PBKDF2 when deriving the key. While this will make the database open faster, it is significantly weaker from a security perspective. Thus it is not generally recommended. That said, here is the information on how to reduce the KDF iterations: