Optically tunable intramolecular charge transfer dyes for vacuum deposited bulk heterojunction solar cells

Abstract

We present the tunability of the photophysical and electrochemical properties of a series of intramolecular charge transfer compounds by facile molecular design and synthesis. The photovoltaic performances based on these sublimable materials and C(60) bulk heterojunction cells are compared and reported. The structural modification of the charge transfer dyes altered not only the electronic properties, but also the morphology of the bulk heterojunction thin films, as revealed by AFM and SEM studies. Addition of PEDOT:PSS between the ITO and the photoactive layer improved the hole injection from the photosensitizer into the anode, and the overall power conversion efficiency is also enhanced.

Synthesis, Characterization, and Electropolymerization of Extended Fused-Ring Thieno[3,4-b]pyrazine-Based Terthienyls

“…After collection via filtration, the products can then be purified by simple solvent washes to give high purity products in nearly quantitative yields (90%–99%). Previous reported yields of T3 – T5 have been in the range of 62%–83% [45,50,52], and it is our belief that the difference in the isolated yields reported here is completely a result of the higher quality of the diamine 10 .…”

“…These are the same methods previously reported for a variety of traditional TP-based terthienyls [23,55,56], as well as various extended fused-ring analogues [23,45,50,52], and involve the initial Stille cross-coupling of the common precursor 2,5-dibromo-3,4-dinitrothiophene ( 8 ) [57] with 2-(tributylstannyl)thiophene to generate 3′,4′-dinitro-2,2′:5′,2″-terthiophene ( 9 ) [55]. The critical step in this synthetic route is then reduction of 9 to the corresponding diamine 10 .…”

“…While the majority of TP-based materials utilize various 2,3-difunctionalized TP monomers, a number of extended fused-ring analogues (Figure 2, 3 – 7 ) [36] have also been utilized as potentially improved building blocks in conjugated materials [23,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54]. Such extended fused-ring analogues have included acenaphtho[1,2- b ]thieno[3,4- e ]pyrazines ( 3 ) [37,38,39,40,41,42,43,44,45,46,47], dibenzo[ f,h ]thieno[3,4- b ]quinox-alines ( 4 ) [45,46,47,48,49,50,51], thieno[3′,4′:5,6]pyrazino[2,3- f ][1,10]phenanthroline ( 5 ) [52,53], trithieno[3,4- b :3′,2′- f :2″,3″- h ]quinoxaline ( 6 ) [44,54], and trithieno[3,4- b :2′,3′- f :3″,2″- h ]quinoxaline ( 7 ) [44,54].…”

“…Such extended fused-ring analogues have included acenaphtho[1,2- b ]thieno[3,4- e ]pyrazines ( 3 ) [37,38,39,40,41,42,43,44,45,46,47], dibenzo[ f,h ]thieno[3,4- b ]quinox-alines ( 4 ) [45,46,47,48,49,50,51], thieno[3′,4′:5,6]pyrazino[2,3- f ][1,10]phenanthroline ( 5 ) [52,53], trithieno[3,4- b :3′,2′- f :2″,3″- h ]quinoxaline ( 6 ) [44,54], and trithieno[3,4- b :2′,3′- f :3″,2″- h ]quinoxaline ( 7 ) [44,54]. Extended fused-ring TPs are generally applied as stronger acceptors in D-A materials [47], yet these monomers are in reality ambipolar units in the same manner as traditional TPs [35].…”

Synthesis and photovoltaic properties of thieno[3,4-b ]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d ]imidazole-containing conjugated polymers

“…Later, the nonlinear optical and electrochromic properties were investigated . The recent research trend is directed toward the applications in FETs and SCs . Bao and coworkers reported the high‐performance semiconducting polymers with fluorene or bithiophene comonomer units .…”