Nowadays, the state-of-the-art photovoltaic performance of OSCs based on fused-ring polymers can indeed rival those of polycrystalline silicon solar cells. [5][6][7][8][9][10] However, fused-ring polymers always present large synthetic complexity (SC > 30%) due to their tedious synthetic procedures and complicated post-purification, which inevitably results in high cost (>1000 $ g −1 ) and leads to that they can seldom be prepared in a high quantity (>10 g). The high cost, as well as poor scalability, greatly hamper the applications of fused-ring polymers in OSCs commercialization. [11][12][13][14] Therefore, developing poly mers with low SC but still featuring good photovoltaic performance is urgent and significant for the further development of OSCs.Compared to fused-ring polymers, poly(3-hexylthiophene) (P3HT) should be the admittedly simplest polymer applying in OSCs, which is not only ascribed to its simple molecular structure but also attributed to its facile synthesis. [15][16][17] Yet, most P3HT-based OSCs show inferior efficiency with value of less than 10%, which is partially ascribed to the shallow highest occupied molecular orbital energy (E HOMO ) level of P3HT. [18][19][20] During the past decades, introducing electron-withdrawing groups or conjugated Fused-ring electron donors boost the efficiency of organic solar cells (OSCs), but they suffer from high cost and low yield for their large synthetic complexity (SC > 30%). Herein, the authors develop a series of simple non-fused-ring electron donors, PF1 and PF2, which alternately consist of furan-3-carboxylate and 2,2′-bithiophene. Note that PF1 and PF2 present very small SC of 9.7% for their inexpensive raw materials, facile synthesis, and high synthetic yield. Compared to their all-thiophene-backbone counterpart PT-E, two new polymers feature larger conjugated plane, resulting in higher hole mobility for them, especially a value up to ≈10 −4 cm 2 V −1 •s for PF2 with longer alkyl side chain. Meanwhile, PF1 and PF2 exhibit larger dielectric constant and deeper electronic energy level versus PT-E. Benefiting from the better physicochemical properties, the efficiencies of PF1-and PF2-based devices are improved by ≈16.7% and ≈71.3% relative to that PT-E-based devices, respectively. Furthermore, the optimized PF2-based devices with introducing PC 71 BM as the third component deliver a higher efficiency of 12.40%. The work not only indicates that furan-3-carboxylate is a simple yet efficient building block for constructing non-fused-ring polymers but also provides a promising electron donor PF2 for the low-cost production of OSCs.
