Random D1-A1-D1-A2 terpolymers based on diketopyrrolopyrrole and benzothiadiazolequinoxaline (BTQx) derivatives for high-performance polymer solar cells

• Published in: New journal of chemistry 2019-04, Vol.43 (14), p.5325-5334
• Main Authors: Keshtov, M. L, Kuklin, S. A, Konstantinov, I. O, Ostapov, I. E, Makhaeva, E. E, Nikolaev, A. Yu, Xie, Zh, Zou, Y, Sharma, Ganesh D
• Format: Article
• Language: English
• Subjects: Carrier mobility; Composition; Current carriers; Energy levels; Optical properties; Optimization; Photovoltaic cells; Polymers; Solar cells; Terpolymerization; Terpolymers
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c8nj05905e

We synthesized and characterized a series of new random terpolymers composed of two electron-accepting blocks, diketopyrrolopyrrole (DPP) and benzothiadiazolequinoxaline (BTQx), and one electron-donating benzo[1,2- b :4,5- b ′]dithiophene (BDT) unit with different molar ratios of the BTQx block to DPP block (25%, 50%, and 75% BTQx). The random terpolymers compositional effects on the physicochemical properties and photovoltaic performances were studied. Different compositions of DPP and BTQx blocks in the conjugated backbone of the terpolymers had a crucial effect on the electrochemical and optical properties of the random terpolymers. These terpolymers were employed as a donor along with PC 71 BM as an acceptor for solution-processed polymer solar cells. Among all the terpolymers, P13 (BDT-DPP50-BTQx50) with a monomer composition of BTQx and DPP (50 : 50) blocks showed excellent light-collecting ability, high charge-carrier mobility, and a low-lying HOMO energy level. PSCs based on P13 (BDT-DPP50-BTQx50) exhibited a V oc of 0.86 V, a J sc of 15.74 mA cm −2 , and an FF of 0.68, leading to a high PCE of 9.20%, which is higher than that for D-A copolymers, i.e. , P11 (7.37%) and P15 (8.11%). These results demonstrate that random terpolymerization is a simple and practical approach for optimization of a conjugated polymer donor for efficient polymer solar cells. The overall power conversion efficiency of the polymer solar cell based on P13 (DPP/BTQx ratio is 1/1) showed the highest value of 9.20% with a V oc of 0.86 V, J sc of 15.74 mA cm −2 , and FF of 0.68.