2-Alkyl-5-thienyl-Substituted Benzo[1,2-b:4,5-b′]dithiophene-Based Donor Molecules for Solution-Processed Organic Solar Cells

TLDR: Two novel, symmetrical, and linear A-D-A-type π-conjugated donor molecules each containing a planar electron-rich 2-octylthiene-5-yl-substituted benzodithiophene (TBDT) unit as the core are synthesized and end-capped with electron-deficient cyanoacetate (CNR) or dicyanovinyl (CN) units.

Abstract: In this study, we have strategically designed and convergently synthesized two novel, symmetrical, and linear A–D–A-type π-conjugated donor molecules (TBDTCNR, TBDTCN), each containing a planar electron-rich 2-octylthiene-5-yl-substituted benzodithiophene (TBDT) unit as the core, flanked by octylthiophene units and end-capped with electron-deficient cyanoacetate (CNR) or dicyanovinyl (CN) units. We thoroughly characterized both of these materials and investigated the effects of the end groups (CNR, CN) on their optical, electrochemical, morphological, and photovoltaic properties. We then fabricated solution-processed bulk heterojunction organic solar cells incorporating TBDTCNR and TBDTCN. Among our tested devices, the one containing TBDTCNR and [6,6]-phenyl-C61-butyric acid methyl ester in a 1:0.40 ratio (w/w) exhibited the highest power conversion efficiency (5.42%) with a short-circuit current density (Jsc) of 9.08 mA cm–2, an open circuit voltage (Voc) of 0.90 V, and an impressive fill factor (FF) of ...

Figures

Figure 6. EQE curves of BHJ solar cell devices incorporating TBDTCNR:PC61BM (1:0.4, w/w) and TBDTCN:PC61BM (1:0.6, w/ w) blends (optimized weight ratios).

Figure 7. Tapping-mode AFM phase images of blend films cast from CHCl3 solutions for (a, b) TBDTCNR:PC61BM at weight ratios of (a) 1:0 and (b) 1:0.4 and (c, d) TBDTCN:PC61BM at weight ratios of (c) 1:0 and (d) 1:0.6.

Figure 1. Chemical structures of TBDTCNR and TBDTCN.

Figure 2. Normalized UV−vis absorption spectra of TBDTCNR and TBDTCN as dilute solutions in CHCl3 and as thin films on glass surfaces at room temperature.

Figure 4. XRD patterns of TBDTCNR and TBDTCN films spincoated from CHCl3. Inset: Expanded view of the pattern for TBDTCNR and TBDTCN in the range 6−14 Å.

Figure 3. Cyclic voltammograms of TBDTCNR and TBDTCN as thin films (scan rate = 100 mV s−1).

Frequently asked questions

Q1. What are the contributions mentioned in the paper "2‐alkyl-5-thienyl-substituted benzo[1,2‐b:4,5‐b′]dithiophene-based donor molecules for solution-processed organic solar cells" ?

In this study, the authors have strategically designed and convergently synthesized two novel, symmetrical, and linear A− D−A-type π-conjugated donor molecules ( TBDTCNR, TBDTCN ), each containing a planar electron-rich 2-octylthiene-5-ylsubstituted benzodithiophene ( TBDT ) unit as the core, flanked by octylthiophene units and end-capped with electron-deficient cyanoacetate ( CNR ) or dicyanovinyl ( CN ) units. The authors thoroughly characterized both of these materials and investigated the effects of the end groups ( CNR, CN ) on their optical, electrochemical, morphological, and photovoltaic properties. The FFs of these solutionprocessed small-molecule organic solar cells ( SMOSCs ) are outstanding when compared with those recently reported for benzodithiophene ( BDT ) -based SMOSCs, because of the high crystallinity and excellent stacking properties of the TBDT-based compounds.