All-polymer solar cells have been actively studied due to their advantages such as lightweight, low-cost, and high throughput compared to conventional silicon solar cells . Nevertheless, there are many problems to commercialize the polymer solar cells due to the poor stability and low mechanical reliability . In particular, it is well known that the blend ratio of polymer donor and acceptor is highly correlated to the efficiency of the polymer solar cells . However, most of the previous studies have mainly focused on the photoelectric performances depending on the blend ratio without consideration of the mechanical characteristics of the polymer solar cells. In this study, we examined the fracture energy of polymer solar cells according to the donor/acceptor blend ratio by double cantilever beam (DCB) test. As a result, the high fracture resistance of the polymer solar cell above 3.0 J/m2 could be obtained over the broad donor/acceptor ratio by using high molecular weight polymer acceptor. (Mn = 115 kg mol-1 ) In addition, the surface morphology of the fractured polymer solar cells was analyzed to reveal the change of the fracture behavior according to the donor/acceptor blend ratio. This study demonstrates the importance of the donor/acceptor blend ratio for the mechanically robust polymer solar cells.