I have not used Postgre with Phalcon, but It should be same as other drivers. Look for the comment below :)
$di->setShared('db', function() use ($databaseCredentials) {
return new \Phalcon\Db\Adapter\Pdo\Mysql([
'host' => $databaseCredentials->host,
'username' => $databaseCredentials->username,
'password' => $databaseCredentials->password,
'dbname' => $databaseCredentials->name,
'charset' => 'utf8',
'options' => [
\PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8, CHARACTER SET utf8;',
\PDO::ATTR_PERSISTENT => true,
\PDO::ATTR_STRINGIFY_FETCHES => false // <-- SEE HERE!!!
]
]);
});