Solution-processed bulk heterojunction (BHJ) solar cells based on ternary blends have previously achieved high power conversion efficiencies (PCEs). In this study, we obtained a combination of good cell performance and high thermal stability for an inverted ternary organic solar cell based on a single polymer donor (PTB7-Th) and two acceptors: one a polymer (N2200) and the other a fullerene component (PC71BM). The ternary blended film based on PTB7-Th:N2200:PC71BM at a composition of 2:0.5:2.5 (w/w/w) featured suitable cascade energy levels, a broad comprehensive absorption region, and smooth interfaces; its corresponding device exhibited a best PCE of 6.2%, an open-circuit voltage of 0.82 V, and a short-circuit current density of 14.4 mA cm(-2). After introducing 1% of 1,8-diiodoctane (DIO), the highest PCE reached 7.7%. Furthermore, this ternary cell exhibited good long-term thermal stability after annealing at 100 degrees C for 1000 h.