Is it permissible to read supplications written on a paper outside and during prayer due to poor memorization?

It is permissible to read a supplication from a paper when one has not memorized it, but memorizing it and reciting it with presence of heart and devotion is more complete. As for prayer, it is better for the supplication to be memorized and concise. There is no harm in reading it from a paper during the Tashahhud (definition) or between the two prostrations, but memorization is closer to achieving devotion.