In this work, the impact of temperature-dependent aggregation behaviors in benzodithiophene (BDT)-based polymer donors (P(D)s) on the electrical, morphological, and photovoltaic performances of all-polymer solar cells (all-PSCs) is investigated. Two P(D)s, PBDB-T and PBDB-Bz, with thienyl or benzothienyl side chains and identical backbones are prepared. In contrast to PBDB-T, PBDB-Bz with bulkier side chains exhibits strong aggregation behavior in solution independent of temperatures between 20 and 100 degrees C. Notably, PBDB-Bz-based all-PSCs show a power conversion efficiency (PCE) of over 9% without any solvent additives (SAs) or thermal annealing (TA), whereas these treatments are inevitable in optimizing the PCE of PBDB-T-based all-PSCs. Furthermore, high PCEs for the PBDB-Bz-based devices are maintained, irrespective of their processing temperature (T-proc). However, the PCEs of PBDB-T-based devices are strongly dependent on their SA, TA, and T-proc, conditions. This phenomenon is due to the robust nature of the domain crystallinity and blend morphology of PBDB-Bz blends at different T(proc)s, resulting in T-proc-tolerant charge mobilities and PCE values. Thus, the development of P(D)s with temperature-insensitive, strong aggregation behavior is crucial in producing reproducible, T-proc tolerant, and additive-free high-performance all-PSC devices.