Enhanced Efficiency and Long-Term Stability of Perovskite Solar Cells by Synergistic Effect of Nonhygroscopic Doping in Conjugated Polymer-Based Hole-Transporting Layer

Chang Woo Koh, Jin Hyuck Heo, Mohammad Afsar Uddin, Young Wan Kwon, Dong Hoon Choi, Sang Hyuk Im, Han Young Woo

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

A face-on oriented and p-doped semicrystalline conjugated polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole)] (PPDT2FBT), was studied as a hole-transport layer (HTL) in methylammonium lead triiodide-based perovskite solar cells (PVSCs). PPDT2FBT exhibits a mid-band gap (1.7 eV), high vertical hole mobility (7.3 × 10-3 cm2/V·s), and well-aligned frontier energy levels with a perovskite layer for efficient charge transfer/transport, showing a maximum power conversion efficiency (PCE) of 16.8%. Upon doping the PPDT2FBT HTL with a nonhygroscopic Lewis acid, tris(pentafluorophenyl)borane (BCF, 2-6 wt %), the vertical conductivity was improved by a factor of approximately 2, and the resulting PCE was further improved up to 17.7%, which is higher than that of standard PVSCs with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as an HTL. After BCF doping, the clearly enhanced carrier diffusion coefficient, diffusion length, and lifetime were measured using intensity-modulated photocurrent and photovoltage spectroscopy. Furthermore, compared to the standard PVSCs with spiro-OMeTAD, the temporal device stability was remarkably improved, preserving the -60% of the original PCE for 500 h without encapsulation under light-soaking condition (1 sun AM 1.5G) at 85 °C and 85% humidity, which is mainly due to the highly crystalline conjugated backbone of PPDT2FBT and nonhygroscopic nature of BCF. In addition, formamidinium lead iodide/bromide (FAPbI3-xBrx)-based PVSCs with the BCF-doped PPDT2FBT as an HTL was also prepared to show 18.8% PCE, suggesting a wide applicability of PPDT2FBT HTL for different types of PVSCs.

Original languageEnglish
Pages (from-to)43846-43854
Number of pages9
JournalACS Applied Materials and Interfaces
Volume9
Issue number50
DOIs
Publication statusPublished - 2017 Dec 20

Keywords

  • hole-transport material
  • nonhygroscopic doping
  • p-type dopant
  • perovskite solar cell
  • semicrystalline polymer

ASJC Scopus subject areas

  • Materials Science(all)

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