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6944795 
Journal Article 
Photovoltaic Properties of DPP-based Two- and Three-component Polymers 
Zhang, ZQ; Liu, Z; Yan, KR; Li, H; Liu, W; Lu, X; Li, H; Chen, HZ; Li, C; , 
2018 
SCIENCE PRESS 
BEIJING 
2 
295-303 
WOS:000429059200017 
Diketopyrrolopyrrole (DPP) is attractive for building conjugated polymers for polymer solar cell (PSC) and organic field effect transistor (OFET). Yet the usual access to DPP conjugated polymers is via donor-acceptor (D-A) two-component polymerization. However, the number of excellent polymers based on the D-A combination is still limited, which promotes researchers to explore new strategy for preparation of novel conjugated polymers and to understand their structure-property relationship. In this work, a DPP-based polymer P1 was first obtained with co-polymerization of DPP (A) and alkoxyl benzene (D). Further, two novel polymers (P2 and P3) were developed via introducing a third electron-deficient monomer X (difluoro-benzothiadiazole or naphthalene diimide) in the polymerization process. P1 - P3 polymers (molecular weight: 3.83 x 10(4), 5.30 x 10(4) and 6.56 x 10(4)) showed good solubility in common organic solvents. Due to the hybridization of the molecular orbitals between their three components (D, A and X), P2 and P3 showed narrower bandgaps (1.26 and 1.27 eV) than P1, and their absorption thus red-shifted up to 1000 nm in comparison to that of D-A polymer P1 (bandgap of 1.50 eV). The introduction of electron-deficient monomers also deepened the highest occupied molecular orbital (HOMO) levels of P2 and P3 to -5.28 and -5.33 eV, which was beneficial to a larger open circuit voltage (V-OC) in PSCs. Moreover, the introduction of the third monomer X altered the film properties of the polymers. It showed that P1 with preference of face-on orientation exhibited a good power conversion efficiency (PCE) in PSCs, while P2 demonstrated an improved hole mobility in OFET due to the preferable edge-on orientation. When blended with [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM), P1 showed a PCE of 2.56%, with a V-OC of 0.68 V, a short circuit current density (J(SC)) of 5.71 mA cm(-2) and a fill factor (FF) of 0.66, while P2 gave a lower PCE of 1.79%, with a V-OC of 0.71 V, a J(SC) of 3.91 mA cm(-2) and a FF of 0.65. This work provides references for the design of novel conjugated polymers for PSCs and OFETs.