A Biopolymer Heparin Sodium Interlayer Anchoring TiO2 and MAPbI3 Enhances Trap Passivation and Device Stability in Perovskite Solar Cells

Shuai You; Hui Wang; Shiqing Bi; Jiyu Zhou; Liang Qin; Xiaohui Qiu; Zhiqiang Zhao; Yun Xu; Yuan Zhang; Xinghua Shi; Huiqiong Zhou; Zhiyong Tang

doi:10.1002/adma.201706924

A Biopolymer Heparin Sodium Interlayer Anchoring TiO₂ and MAPbI₃ Enhances Trap Passivation and Device Stability in Perovskite Solar Cells

Adv Mater. 2018 May;30(22):e1706924. doi: 10.1002/adma.201706924. Epub 2018 Apr 18.

Authors

Shuai You^{1

2}, Hui Wang¹, Shiqing Bi¹, Jiyu Zhou³, Liang Qin¹, Xiaohui Qiu¹, Zhiqiang Zhao², Yun Xu⁴, Yuan Zhang³, Xinghua Shi^{1

5}, Huiqiong Zhou¹, Zhiyong Tang^{1

5}

Affiliations

¹ National Center for Nanoscience and Technology, No. 11 ZhongGuanCun BeiYiTiao, Beijing, 100190, P. R. China.
² Collaborative Innovation Center of Henan Province for Energy-Saving Building Materials, Xinyang Normal University, 237 Nanhu Road, Xinyang, 464000, P. R. China.
³ Heeger Research and Development Center, School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, No. 37 Xueyuan Road, Beijing, 100191, P. R. China.
⁴ Center for Medical Device Evaluation, China Food and Drug Administration, Beijing, 100044, China.
⁵ University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China.

PMID: 29667243
DOI: 10.1002/adma.201706924

Abstract

Traps in the photoactive layer or interface can critically influence photovoltaic device characteristics and stabilities. Here, traps passivation and retardation on device degradation for methylammonium lead trihalide (MAPbI₃ ) perovskite solar cells enabled by a biopolymer heparin sodium (HS) interfacial layer is investigated. The incorporated HS boosts the power conversion efficiency from 17.2 to 20.1% with suppressed hysteresis and Shockley-Read-Hall recombination, which originates primarily from the passivation of traps near the interface between the perovskites and the TiO₂ cathode. The incorporation of an HS interfacial layer also leads to a considerable retardation of device degradation, by which 85% of the initial performance is maintained after 70 d storage in ambient environment. Aided by density functional theory calculations, it is found that the passivation of MAPbI₃ and TiO₂ surfaces by HS occurs through the interactions of the functional groups (COO^- , SO₃^- , or Na⁺ ) in HS with undersaturated Pb and I ions in MAPbI₃ and Ti⁴⁺ in TiO₂ . This work demonstrates a highly viable and facile interface strategy using biomaterials to afford high-performance and stable perovskite solar cells.

Keywords: heparin sodium; interface modification; perovskites; stability; trap passivation.