A Narrow-Bandgap n-Type Polymer Semiconductor Enabling Efficient All-Polymer Solar Cells

Shengbin Shi; Peng Chen; Yao Chen; Kui Feng; Bin Liu; Jianhua Chen; Qiaogan Liao; Bao Tu; Jiasi Luo; Mengyao Su; Han Guo; Myung-Gil Kim; Antonio Facchetti; Xugang Guo

doi:10.1002/adma.201905161

A Narrow-Bandgap n-Type Polymer Semiconductor Enabling Efficient All-Polymer Solar Cells

Adv Mater. 2019 Nov;31(46):e1905161. doi: 10.1002/adma.201905161. Epub 2019 Sep 30.

Authors

Shengbin Shi¹, Peng Chen¹, Yao Chen², Kui Feng¹, Bin Liu¹, Jianhua Chen^{1

2}, Qiaogan Liao¹, Bao Tu¹, Jiasi Luo¹, Mengyao Su¹, Han Guo¹, Myung-Gil Kim³, Antonio Facchetti^{2

4}, Xugang Guo¹

Affiliations

¹ Department of Materials Science and Engineering and The Shenzhen Key Laboratory for Printed Organic Electronics, Southern University of Science and Technology (SUSTech), No. 1088, Xueyuan Road, Shenzhen, Guangdong, 518055, China.
² Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.
³ Department of Chemistry, Chung-Ang University, Seoul, 06974, Republic of Korea.
⁴ Flexterra Corporation, 8025 Lamon Avenue, Skokie, IL, 60077, USA.

PMID: 31566274
DOI: 10.1002/adma.201905161

Abstract

Currently, n-type acceptors in high-performance all-polymer solar cells (all-PSCs) are dominated by imide-functionalized polymers, which typically show medium bandgap. Herein, a novel narrow-bandgap polymer, poly(5,6-dicyano-2,1,3-benzothiadiazole-alt-indacenodithiophene) (DCNBT-IDT), based on dicyanobenzothiadiazole without an imide group is reported. The strong electron-withdrawing cyano functionality enables DCNBT-IDT with n-type character and, more importantly, alleviates the steric hindrance associated with typical imide groups. Compared to the benchmark poly(naphthalene diimide-alt-bithiophene) (N2200), DCNBT-IDT shows a narrower bandgap (1.43 eV) with a much higher absorption coefficient (6.15 × 10⁴ cm^-1 ). Such properties are elusive for polymer acceptors to date, eradicating the drawbacks inherited in N2200 and other high-performance polymer acceptors. When blended with a wide-bandgap polymer donor, the DCNBT-IDT-based all-PSCs achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm. Such efficiency greatly outperforms those of N2200 (6.13%) and the naphthalene diimide (NDI)-based analog NDI-IDT (2.19%). This work breaks the long-standing bottlenecks limiting materials innovation of n-type polymers, which paves a new avenue for developing polymer acceptors with improved optoelectronic properties and heralds a brighter future of all-PSCs.

Keywords: all-polymer solar cells; dicyanobenzothiadiazole; high absorption coefficient; narrow bandgap; polymer acceptors.

Abstract

Grants and funding