Stability issue is the core restriction for the application of organic solar cells (OSCs). However, state-of-the-art OSCs based on bulk-heterojunction concept suffer from stability problems caused by the severe morphological changes upon thermal or illumination stress [1]. Single-component concept, enabled by the covalently-bonded structure with donor and acceptor in one molecule, presents attractive advantages such as a simplification of device fabrication and a stabilization of microstructure [2]. Recently, with the rapid improvement of efficiency from 2-3% to 8.4% for single-component organic solar cells (SCOSCs), the reports on their stability however are scanty. In this work, we for the first time systematically investigated the stability under thermal and illumination stress of a series of SCOSCs based on polymeric (SCP3, PBDBPBI-Cl) and molecular (Dyad1, 2, 3, 4) materials. Under thermal pressure, double-cable polymer-based SCOSCs exhibited excellent thermal stability with no degradation at 90 ^oC for 3000 hours, partially attributed to the high temperatures (around 200 ^oC) for post-treating active layer during device fabrication. Such rather high annealing temperatures are plausible to create microstructure arrangements which are in thermodynamic equilibrium after cooling down. Furthermore, without precedent, we studied the thermal stability comparison among a series of SCOSCs based on D-A small molecules (Dyad1, 2 and 3) with the same donor and acceptor units but differently long alkyl space linkers. Since macroscopic diffusion of molecules is excluded in these dyads, the length of the spacer can only provide the necessary flexibility for sub-nm rearrangements caused by thermal stress. Interestingly, dyads showed a distinctly different behavior, Dyad1 with the shortest linker exhibiting the highest thermal stability, while Dyad3 with the longest linker showing the worst thermal stability [3]. This highlights the need for further in-depth studies on the dual importance of spacer length for performance and stability. Moreover, Dyad1-based SCOSCs exhibited extraordinary illumination stability, retaining 98% of the initial PCE under concentrated light equal to 7.5-suns for over 1000 hours, which could be among the highest illumination stability for solution-processed OSCs. Based on the outstanding stability, SCOSCs could be an ideal candidate to study the ultimate stability under extremely rugged accelerating conditions such as high temperature and concentrated light. Since the morphological evolution is excluded, SCOSCs could serve as a model system to selectively study interface degradation. In the near future, SCOSCs will see a prospective renaissance with 10% efficiency and 20 years lifetime for industrial applications.