I am interested in references that explain 'introspective research' as a research methodology, but also references of 'design research' in which this method was used.
I would also suggest getting to know the phenomenological approach for a concept of introspection as a scientific research method. You can find introduction how to use phenomenology in design research for example in "The UX Book" by Hartson & Pyla, 2012.
More philosophical explanations on introspection can be found eg. in "Phenomenological research methods" by Moustakas, 1994. Also Chalmers has written about phenomenology as a method to study conscious experiences. In addition Daniel Dennett (2003, Who’s On First - Heterophenomenology Explained) has proposed a extension to the first-person perspective by including third-person perspective (= collaboration with a researcher), which he calls heterophenomenology.