Synthesis and characterization of naphtho[2,1-b:3,4-b′]dithiophene-based polymers with extended π-conjugation systems for use in bulk heterojunction polymer solar cells

Abstract

Two novel polymeric semiconductor materials based on naphtho[2,1‐b:3,4‐b']dithiophene (NDT), PNDT‐TTT and PNDT‐TET, were designed and synthesized. These synthesized polymers were tested in bulk heterojunction solar cells as blends with the acceptor [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM). PNDT‐TTT contained tri‐thiophene units, and PNDT‐TET contained bi‐thiophene units coupled by ethylenic linkages. Comparison to the properties of PNDT‐T, which contained single thiophene units, these polymers exhibit red‐shifted absorption spectra as a result of the enhanced conjugation lengths. These effects resulted in high short circuit currents (JSC) in the organic solar cells. The PNDT‐TET‐ and PNDT‐TTT‐based devices exhibited considerably better photovoltaic performances, with power conversion efficiencies of 3.5 and 3.3%, respectively, compared to the PNDT‐T‐based device (1.3%). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4742–4751

Naphtho[2,1‐b:3,4‐b′]dithiophene‐based Bulk Heterojunction Solar Cells: How Molecular Structure Influences Nanoscale Morphology and Photovoltaic Properties

“…These results are based on the papers previously reported by our group 16. 17 From Figure 7 a, it can be found that PNDT ‐ T solution exhibits two maximum absorption peaks ( λ max ) at λ= 523 nm and 555 nm whereas the λ max for PNDT ‐ TTT is redshifted slightly to λ= 539 nm and 578 nm, due to the longer π‐conjugation length in the PNDT ‐ TTT polymer 17. Compared with the two polymers, PNDT ‐ TT solution exhibits a further redshifted absorption profile, which can be ascribed to the stronger intermolecular stacking in the PNDT ‐ TT polymer 29.…”

“…The details of the syntheses have been reported previously 16. 17 The three polymers were soluble in commonly used chlorinated solvents such as chloroform, chlorobenzene, and o ‐dichlorobenzene (the solubility of the PNDT ‐ T , PNDT ‐ TT , and PNDT ‐ TTT was 13, 10, and 12 g L −1 , respectively.). Phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM), the fullerene derivative (99.5 %) used as the electron acceptor, was obtained from Nano‐C.…”

Donor-acceptor-structured naphtodithiophene-based copolymers for organic thin-film transistors

“…PNDT‐B showed ambipolar characteristics while PNDT‐TBT showed p‐type character is 100 times better than n‐type character. In addition, both polymers with D‐A structure showed similar or lower mobility compared with PNDT‐T and PNDT‐TT with D‐D structure . Thus, it is carefully suggested that backbone planarity of polymer is more important than D‐A interaction in PNDT‐derivatives.…”

“…The chemical structures and synthetic routes to the new polymers are shown in Scheme . NDT was synthesized by thiophene‐centered oxidative cyclization according to previously reported procedures . PNDT‐B was synthesized by a Suzuki reaction of 2,9‐dibromo‐4,5‐bis(2‐octyldodecyloxy)naphtho[2,1‐b:3,4‐b′]dithiophene and 4,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)benzo[c][1,2,5]thiadiazole.…”

A unique concept of copolymer composed of main chain donor and side chain acceptor for promising bulk heterojunction solar cells

“…Becke's three parameter gradient corrected functional (B3LYP) with a polarized 6-31 G** basis was used for full geometry optimization. Methyl alkyl groups were used in place of the bulky alkyl substituents to limit computation time, since they do not significantly affect the equilibrium geometry and thus the electronic properties [25]. As depicted in Fig.…”