There are some academical websites where you can find papers about bitcoin:
- Jstor.org. In there, you will find a good number of academical paper, but the problem is you will need to join towards an institution if you don't want to pay.
- Research Gate. This is like an academic-social media in which many academics and researchers upload their current work. You will find in there some good researchers about bitcoin going on, as well as some (and free) articles: https://www.researchgate.net/topic/Bitcoin
- Academia. edu. The same like Research Gate: this is a social-academic-media place with thousands of papers with free-download available. http://www.academia.edu/Documents/in/Bitcoin
- Cabra, another place with some good papers about bitcoin (i think this is fully dedicated to the crypto world, but I haven't look into it seriously yet): https://cdecker.github.io/btcresearch/
I hope it helps.