Improved Stability of Interfacial Energy-Level Alignment in Inverted Planar Perovskite Solar Cells

Soeun Im, Wanjung Kim, Wonseok Cho, Dongguen Shin, Do Hyung Chun, Ryan Rhee, Jung Kyu Kim, Yeonjin Yi, Jong Hyeok Park, Jung Hyun Kim

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Even though poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been commonly used as a hole extraction layer (HEL) for p-i-n perovskite solar cells (PSCs), the cells' photovoltaic performance deteriorates because of the low and unstable work functions (WFs) of PEDOT:PSS versus those of a perovskite layer. To overcome this drawback, we synthesized a copolymer (P(SS-co-TFPMA)) ionomer consisting of PSS and tetrafluoropropylmethacrylate (TFPMA) as an alternative to conventional PEDOT:PSS. The PEDOT:P(SS-co-TFPMA) copolymer solution and its film exhibited excellent homogeneity and high phase stability compared with a physical mixture of TFPMA with PEDOT:PSS solution. During spin coating, a self-organized conducting PEDOT:P(SS-co-TFPMA) HEL evolved and the topmost PEDOT:P(SS-co-TFPMA) film showed a hydrophobic surface with a higher WF compared to that of the pristine PEDOT:PSS film because of its chemically bonded electron-withdrawing fluorinated functional groups. Interestingly, the WF of the conventional PEDOT:PSS film dramatically deteriorated after being coated with a perovskite layer, whereas the PEDOT:P(SS-co-TFPMA) film represented a relatively small influence. Because of the superior energy-level alignment between the HEL and a perovskite layer even after the contact, the open-circuit voltage, short-circuit current, and fill factor of the inverted planar p-i-n PSCs (IP-PSCs) with PEDOT:P(SS-co-TFPMA) were improved from 0.92 to 0.98 V, 18.96 to 19.66 mA/cm2, and 78.96 to 82.43%, respectively, resulting in a 15% improvement in the power conversion efficiency vs that of IP-PSCs with conventional PEDOT:PSS. Moreover, the IP-PSCs with PEDOT:P(SS-co-TFPMA) layer showed not only improved photovoltaic performance but also enhanced device stability due to hydrophobic surface of PEDOT:P(SS-co-TFPMA) film.

Original languageEnglish
Pages (from-to)18964-18973
Number of pages10
JournalACS Applied Materials and Interfaces
Volume10
Issue number22
DOIs
Publication statusPublished - 2018 Jun 6

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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