Recent progress, particularly with Y-series non-fullerene acceptors (NFAs), has propelled the power conversion efficiency (PCE) of single-junction organic photovoltaics (OPVs) beyond 19%.[1] This improvement pushes the need to design new donor polymers that effectively pair with NFAs. However, many high-performing donor polymers are expensive due to complex synthesis processes and costly raw materials. Thus, the design of low-cost donor polymers is crucial for large-scale production and commercial adoption. In this study, we explored the charge generation mechanism in new low-cost donor polymer FO6-T blends, which presents high crystallinity challenges and new potentials for efficient OPVs. When blended with the NFA L8BO, FO6-T achieves a notable PCE of 15%.[2] We identified two distinct polaron states in FO6-T: one associated with disordered domains and the other with crystalline domains, as evidenced by cyclic voltammetry (CV) and spectroelectrochemistry (SEC) measurements. These findings align with the reported FO6-T’s semi-crystalline morphology3. To gain deeper insights, transient absorption spectroscopy (TAS) was employed across timescales from femtoseconds (fs) to seconds (s) to investigate charge dynamics within these domains. Upon photoexcitation, FO6-T excitons rapidly converted into polaron states within a few picoseconds (ps). Polaron states in the disordered domains near the donor/acceptor (D/A) interface transferred to crystalline phases via an energy cascade within 20 ps. The crystalline phases played an important role in stabilizing the separated polarons, which exhibited lifetimes extending into the microsecond (μs) range, as shown by μs-TAS measurements. Then we studied the high-performing FO6-T:L8-BO. The two polaron states of FO6-T persist in the FO6-T/L8-BO blend, revealed by fs-TAS. Furthermore, Förster resonance energy transfer (FRET) was observed under donor excitation, supported by the TAS kinetic analysis. The highly overlapping emission spectrum of FO6-T and the absorption spectrum of L8-BO also support the FRET observation. To investigate the impact of findings discussed above on device performances, a series of D/A ratio studies was conducted. The FO6-T/L8-BO blend exhibited exceptional tolerance to D/A ratios ranging from 2:1 to 1:10. These findings underscore the potential of low-cost, simple donor polymers like FO6-T in achieving high-efficiency and semi-transparent OPVs, paving the way for broader commercialization and innovative applications.