Unfortunately, jdk8+ is not tested and certified with Informatica 9.1.0. Informatica will ship the java along with the installers and recommend to use the same version.
In addition please note Informatica 9.1 has reached EOL on January 2017. Please check this document on the portal for more details:
You can upgrade to higher version which will support latest java version.
Pleae note that the Java version support is a complex matter. In older versions of PowerCenter (until 10.2.something, if memory serves me right) it was mandatory to stick to the exact version installed with PowerCenter (resp. installed on AIX as requested by Informatica for each version). There was absolutely no way to upgrade the JDK in any way, except for installing a later PowerCenter version which brings / uses a new JDK version.
There is a Support Statement available which details all these things. In short, the JDK / JRE versions are still fixed per PowerCenter version, in some cases it is allowed by Informatica to perform a minor-version upgrade (e.g. from 1.8.217 to 1.8.234), but you really should check the Support Statement: