Tetrathienodibenzocarbazole Based Donor–Acceptor Type Wide Band-Gap Copolymers for Polymer Solar Cell Applications

Two new donor–acceptor alternating wide band gap copolymers, <b>PTTDBC-PhQC8</b> and <b>PTTDBC-BTC12</b>, based on an electron-rich tetrathienodibenzocarbazole (<b>TTDBC</b>) donor have been designed and synthesized, wherein two additional thienyl rings are fused into a 2,7-dithienylcarbazole skeleton to reinforce the structural coplanarity and rigidity of polymers. The quinoid thiophene in <b>TTDBC</b> can endow not only a wide optical band gap (∼1.9 eV) but also a deep HOMO (∼5.3 eV) for the resulting polymers. The conventional configuration solar cells based on <b>PTTDBC-BTC12</b> exhibit a large <i>V</i>_oc of 0.91 V and a power conversion efficiency of 4.30% (with a <i>J</i>_sc of 9.27 mA cm^–2 and a FF of 0.51), while a slightly higher PCE of 4.50% can be achieved for the inverted structure devices. We believe that these wide band gap polymers have potential to be used for tandem cell applications