Naphthobistriazole-based wide bandgap donor polymers for efficient non-fullerene organic solar cells: Significant fine-tuning absorption and energy level by backbone fluorination

• Published in: Nano energy Vol. 53; pp. 258 - 269
• Main Authors: Tang, Dongsheng, Wan, Jiahui, Xu, Xiaopeng, Lee, Young Woong, Woo, Han Young, Feng, Kui, Peng, Qiang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2018
• Subjects: Fluorination; Naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole); Non-fullerene polymer solar cells; Ternary blend solar cells; Wide bandgap polymer donors; Wide bandgap polymer donors; Naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole); Fluorination; Non-fullerene polymer solar cells; Ternary blend solar cells
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2018.08.059

In this work, two wide bandgap polymers of PDTT-TZNT and PDTF-TZNT were developed by Stille-coupling of naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) (TZNT) acceptor unit with bithiophene (DTH) and fluorinated bithiophene (DTF), respectively. These polymers exhibited a wide bandgap over 1.84 eV. The fluorinated PDTF-TZNT had lower highest occupied molecular orbital HOMO level (− 5.24 eV), higher molar absorption coefficient (1.28 × 105 M−1 cm−1), and higher molecular packing order. Using a low bandgap 3,9-bis(2-methylene-(5&6-methyl-(3-(1,1-dicyanomethylene)-indanone)))−5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (IT-M) as the electron acceptor, the PDTF-TZNT:IT-M devices generated a higher power conversion efficiency (PCE) of 10.05%. To make up the weak absorption of above binary blend of PDTF-TZNT:IT-M in the short wavelength region and increase the device performance further, a large bandgap small molecular acceptor of 5,5,10,10,15,15-hexabutyl-2,7,12-tri(4-(3-ethylhexyl-4-oxothiazolidine-2-yl)dimalononitrile-benzothiadiazole)-truxene (meta-TrBRCN) was added as the second acceptor material to fabricate ternary blend PSCs. The meta-TrBRCN could not only expand the absorption range but also fine-tune the blend morphology by stepwise changing its content. When 0.2 of meta-TrBRCN was added, the PCE of PDTF-TZNT:IT-M devices was improved to 11.48%. Two novel naphthobistriazole-based wide bandgap polymers, PDTH-TZNT and PDTF-TZNT, has been developed for non-fullerene polymer solar cells. The fluorinated PDTF-TZNT exhibited a higher PCE of 10.05% in binary PDTT-FTAZ:IT-M devices. By adding 0.2 of meta-TrBRCN as the second acceptor, the related ternary blend devices exhibited a significantly improved PCE of 11.48%. [Display omitted] •Two novel naphthobistriazole-based wide bandgap donor polymers were successfully synthesized and characterized.•The introduced fluorine atoms enabled the PDTF-TZNT:IT-M devices to obtain a higher PCE of 10.05%.•The ternary blend strategy boosted the PCE up to 11.48% in the PDTF-TZNTx:IT-My:meta-TrBRCNz devices.