Efficient Inverted Perovskite Solar Cells by Employing N-Type (D-A1 -D-A2 ) Polymers as Electron Transporting Layer

Ahmed Ali Said; Jian Xie; Yang Wang; Zongrui Wang; Yu Zhou; Kexiang Zhao; Wei-Bo Gao; Tsuyoshi Michinobu; Qichun Zhang

doi:10.1002/smll.201803339

Efficient Inverted Perovskite Solar Cells by Employing N-Type (D-A₁ -D-A₂ ) Polymers as Electron Transporting Layer

Small. 2019 Jul;15(29):e1803339. doi: 10.1002/smll.201803339. Epub 2018 Oct 29.

Authors

Ahmed Ali Said¹, Jian Xie¹, Yang Wang², Zongrui Wang¹, Yu Zhou³, Kexiang Zhao¹, Wei-Bo Gao³, Tsuyoshi Michinobu², Qichun Zhang¹

Affiliations

¹ School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore, Singapore.
² Department of Materials Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan.
³ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.

PMID: 30370590
DOI: 10.1002/smll.201803339

Abstract

It is highly desirable to employ n-type polymers as electron transporting layers (ETLs) in inverted perovskite solar cells (PSCs) due to their good electron mobility, high hydrophobicity, and simplicity of film forming. In this research, the capability of three n-type donor-acceptor₁ -donor-acceptor₂ (D-A₁ -D-A₂ ) conjugated polymers (pBTT, pBTTz, and pSNT) is first explored as ETLs because these polymers possess electron mobilities as high as 0.92, 0.46, and 4.87 cm² (Vs)^-1 in n-channel organic transistors, respectively. The main structural difference among pBTT, pBTTz, and pSNT is the position of sp² -nitrogen atoms (sp² -N) in the polymer main chains. Therefore, the effect of different substitution positions on the PSC performances is comprehensively studied. The as-fabricated p-i-n PSCs with pBTT, pBTTz, and pSNT as ETLs show the maximum photoconversion efficiencies of 12.8%, 14.4%, and 12.0%, respectively. To be highlighted, pBTTz-based device can maintain 80% of its stability after ten days due to its good hydrophobicity, which is further confirmed by a contact angle technique. More importantly, the pBTTz-based device shows a neglected hysteresis. This study reveals that the n-type polymers can be promising candidates as ETLs to approach solution-processed highly-efficient inverted PSCs.

Keywords: inverted perovskite solar cells; n-type polymers; organic transporting layers; stability of devices.

Abstract

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