Unfortunately, Android does not provide us with a means to record directly from another application. We can only record from the hardware mic. But if you run Hi-Q MP3 Voice Recorder in the background, you can still record Skype conversation, but the quality might not be optimal.
If you are unsure with the recordings’ quality through your phone, please try Hi-Q MP3 Voice Recorder free version before purchasing: Hi-Q MP3 Voice Recorder (Free)