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The auxiliary acceptors of metal complexes can easily regulate the electron-withdrawing ability of electron acceptor and adjust the balance of push–pull electron of D-A-π-A motif dye sensitizers. Two series of the D-(A-π-A)2 motif dye sensitizer (BDTT-im-Co, BDTT-im-Cu, BDTT-im-Zn, BDTT-im-Cd and FL-im-Co, FL-im-Cu, FL-im-Zn, FL-im-Cd) which use metal complexes of pyridineimine derivative as auxiliary acceptor were designed, synthesized, and characterized. The photovoltaic test of eight complex-based dye sensitized solar cells (DSSCs) showed that the short-circuit photocurrent density (JSC) and the power conversion efficiency (PCE) of two series dye sensitizers are sequentially increased. BDTT-im-Cd have the highest JSC of 15.58 mA cm−2 and the PCE of 9.13% under AM 1.5 irradiation, which may be due to that electron-withdrawing ability of the auxiliary acceptor metal complexes of pyridineimine derivative can be changed by the strength of coordination bond of the complexes. They also show good terminal stability with decomposition temperatures (Td) higher than 300 °C. [ABSTRACT FROM AUTHOR]

Four metal complexes BDTT‐PCd, BDTT‐PZn, BDTT‐PCu, and BDTT‐PCo with the symmetrical structure were designed, synthesized, and characterized, which would be used as D‐(A‐π‐A)2 motif dye sensitizers. These complexes adopt Cd(II), Zn(II), Cu(II), and Co(II) complexes as auxiliary electron acceptors (A), thienylbenzo[1,2‐b:4,5‐b′]dithiophene (BDTT) as electron donor (D), and the 8‐quinolinol derivative as the π bridge and the acceptor (A) of D‐(A‐π‐A)2 motif dye sensitizers. The photophysical, electrochemical, and photovoltaic properties of these complexes have been investigated. The four complexes‐based dye‐sensitized solar cells (DSSCs) device exhibited a short‐circuit photocurrent density (Jsc) of 17.51, 17.02, 15.07, and 14.38 mA cm−2 and an attractive power conversion efficiency (η) of 8.82%, 8.32%, 8.03%, and 7.55%, respectively, under the AM 1.5 irradiation (100 mW cm−2). The photovoltaic conversion efficiency (PCE) and the short‐circuit photocurrent density (Jsc) of BDTT‐PCd, BDTT‐PZn, BDTT‐PCu, and BDTT‐PCo are sequentially reduced; it attributed to the difference of the electron‐withdrawing ability of the auxiliary acceptor resulted by the difference of coordination abilities of metal ions Cd(II), Zn(II), Cu(II), and Co(II) with ligand. These results provide strong evidence that D‐(A‐π‐A)2 motif complexes has great potential as promising photosensitizers in the applications of DSSCs. [ABSTRACT FROM AUTHOR]

The eight polymeric metal complexes in both series (BDTT-PP-Cd, BDTT-PP-Zn, BDTT-PP-Cu, BDTT-PP-Ni and BDTT-PBD-Cd, BDTT-PBD-Zn, BDTT-PBD-Cu, BDTT-PBD-Ni) for being used as D-A-(π-A) 2 motif dye sensitizers were designed, synthesized and characterized. They use metal complex of pyridine derivatives as auxiliary electron acceptor, thienylbenzene-[1,2-b:4,5-b' dithiophene (BDTT) as electron donor, and 8-quinolinol derivatives as π-bridge and electron acceptor. Under AM 1.5 irradiation (100 mW cm−2), the devices of dye-sensitized solar cells (DSSCs) based on eight polymeric complexes exhibited short circuit current density (J sc) of 17.39, 15.10, 14.03, 12.61 mA cm−2 and 18.95, 15.58, 14.53, 13.23 mA cm−2 respectively,and their power conversion efficiency (PCE) are 8.94%, 8.09%, 6.87%, 6.34% and 9.76%, 8.55%, 7.02%, 6.51% respectively. The photovoltaic performance test of DSSCs based on eight polymeric metal complexes showed that the PCE of BDTT-PBD-M (M = Cd, Zn, Cu, Ni) is higher than that of BDTT-PP-M (M = Cd, Zn, Cu, Ni) because of the introduction of the methyl group into BDTT-PBD-M and the increase of the absorption coefficient of the dye. For dye sensitizers with the same ligand and different metals, the PCE of BDTT-PP-Ni, BDTT-PP-Cu, BDTT-PP-Zn and BDTT-PP-Cd increase in order, and so does the other series BDTT-PBD-M. It is because of enhancing electron-withdrawing ability of auxiliary electron acceptor with the strength of coordination bond from Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ) and Cd(Ⅱ) with the ligand. These results provide a new way to develop efficient and stable dye sensitizers in the future. [Display omitted] • Metal complex units of pyridine derivatives are used as auxiliary electron acceptors instead of organic groups. • Two series of eight new D-A-(π-A) 2 motifs polymeric metal complexes are synthesized. • The highest PCE of BDTT-PBD-Cd is 9.76%. • The effect of ligand bond type and strength of complexes on PCE is investigated. • These complexes show good thermal stability and the T d is between 176 and 286 °C. [ABSTRACT FROM AUTHOR]