Single-photon solid-state sensors, such as Single Photon Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs), are gradually replacing the traditional Photomultiplier in several applications, ranging from big scientific experiments at CERN, to space missions, to Positron Emission Tomography to automotive LiDAR. On the other hand, an important factor limiting the use of SIPMs and SPADs in space, as well as in HEP, is the qualification and improvement of their radiation tolerance. To this end, Fondazione Bruno Kessler (FBK) is dedicating significant research effort to the study of the radiation damage in SiPMs, through experimental characterization of their characteristics after irradiation, and to the development of innovative structures featuring enhanced radiation tolerance, which will enable a whole set of new applications in space. In this context, the PhD candidate will carry out her/his research in FBK, which is one of the worldwide recognized leaders in the development of SiPMs and SPADs. The activity will focus on the experimental characterization of the electro optical properties of the devices after irradiation with both ionizing and non-ionizing particles, employing and possibly improving the advanced setups and analysis software already available at FBK and exploiting different irradiation facilities that FBK has access to, providing sources of protons, neutrons or x-rays. The PhD candidate will also study innovative detector structures with enhanced radiation tolerance, contributing to their development and becoming proficient in the understanding, characterization and use of silicon detectors for science and industrial applications. Furthermore, she/he will investigate solutions to increase the lifetime and preserve the performances of detectors in space through optimized packaging. The activity will benefit from the strong scientific network built by FBK in the space sector, including GSSI, several partners from INFN, and ESA. The research will be carried out in the context of different, space-focused projects, in which FBK is partner or coordinator, with the role of developing single-photon sensors optimized for space applications: ASTRA, funded by Italian PNRR and coordinated by GSSI, SpaceItUp, funded by ASI / PNRR, and ORBITS, funded by ESA and coordinated by FBK.