A new narrow-bandgap copolymer PBFTT, based on 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDT-2F) as donor unit and octyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT) as acceptor unit, was synthesized as donor material for non-fullerene (NF) polymer solar cells (PSCs) application. Compared to the analogue polymer PTB7-Th, PBFTT with two fluorine atoms in the conjugated side chains of BDT possesses a deeper HOMO energy level of −5.47 eV and a slightly enhanced hole mobility of 3.13 × 10⁻³ cm² V^-1 s^-1 versus (vs.) a HOMO energy level of −5.30 eV and a hole mobility of 1.11 × 10⁻³ cm² V^-1 s^-1 for PTB7-Th. Hence, the corresponding PSCs based on PBFTT:ITIC exhibited an optimal PCE of 9.1% with a V_oc of 0.94 V, a J_sc of 16.0 mA cm⁻², and a FF of 60.5% compared to a PCE of 6.8% with a V_oc of 0.81 V, a J_sc of 14.2 mA cm⁻² and a FF of 59.1% for PTB7-Th:ITIC-based PSCs. Notably, this PCE is among the highest values for the NF-PSCs based on narrow-bandgap polymer without extra treatments. These results indicate that PBFTT is a promising narrow-bandgap polymer donor material for NF-PSCs application.

基于4,8-双（5-（2-（乙基乙基己基）-4-氟噻吩-2-基）苯并[1,2-b：4,5-b']二噻吩（BDT）的新型窄带隙共聚物PBFTT合成了作为供体单元的-2F）和作为受体单元的3-氟噻吩并[3,4- b ]噻吩-2-羧酸辛基酯（TT）作为非富勒烯（NF）聚合物太阳能电池（PSC）应用的供体材料。相比于模拟聚合物PTB7-Th时，PBFTT在BDT的共轭侧链具有两个氟原子具有-5.47电子伏特的更深的HOMO能级和3.13×10稍微增强的空穴迁移率^-3 厘米²  V ^-1 小号^{- 1}与（vs.）HOMO能级为-5.30 eV和空穴迁移率为1.11×10 ^-3PTB7-Th的 cm ²  V ^-1  s ^-1 因此，与PBFTT：ITIC对应的PSC的最佳PCE为9.1％，V _oc为0.94 V，J _sc为16.0 mA cm ^-2，FF为60.5％，而PCE的最佳PCE为6.8％。对于基于PTB7-Th：ITIC的PSC ，V _oc为0.81 V，J _sc为14.2 mA cm ^-2，且FF为59.1％。值得注意的是，该PCE是基于窄带隙聚合物的NF-PSC的最高值，而无需额外的处理。这些结果表明PBFTT 是用于NF-PSC的有前途的窄带隙聚合物供体材料。