Recent empirical research has provided compelling evidence that the proliferation of intellectual property rights (IP) and the fragmentation of patent rights among different patent holders have created barriers to innovation and impediments to the commercialization of scientific discoveries. Legal and economic scholars have suggested that due to the rising number of patent applications, the limited resources in patent offices around the world and the lack of sufficient time to prior art search, examiners have failed to conduct thorough patent examination processes. Moreover, researchers have linked the growing number of overlapping intellectual property rights to the tragedy of the anticommons and to the concept of patent thickets. Multiple studies have been performed in order to develop measures that could verify the existence of patent thickets and to better understand the social and economic impact of fragmentary patent owners. When it comes to the energy sector, the problem of patent thickets is now even more important. As the technological innovation in this sector increases and the energy-related patenting continues to grow, it has been argued that the issue of patent thickets may have a direct impact on investment decisions and the long-run development of this sector. This paper presents an overview of literature on the definition of a patent thicket and summarizes some of the possible factors causing thickets to arise. Additionally, it discusses the recent developments in patent thicket measures and patent thicket identification methods.