Air-Exposure Induced Dopant Redistribution and Energy Level Shifts in Spin-Coated Spiro-MeOTAD Films

• DOI: 10.1021/cm504022q
• Publication Date: 2014-12-29T12:26:49Z
• Authors: Zafer Hawash; Luis K. Ono; Sonia R. Raga; Michael V. Lee; Yabing Qi
• Keywords: Materialteknik; Materials Engineering; 02 engineering and technology; 0210 nano-technology; 7. Clean energy

Doping properties of 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) hole transport layer are investigated by X-ray photoelectron spectroscopy, ultraviolet and atomic force microscopy under air exposure. XPS results reveal that 3 h exposure Li-bis(trifluoromethanesulfonyl)-imide (LiTFSI) doped spiro-MeOTAD to in the migration LiTFSI from bottom top across film. AFM images presence pinholes with an average diameter ∼135 nm a density ∼3.72 holes/μm2. In addition, cross-sectional scanning electron microscope these form channels Optical Fourier transform infrared confirm large diameters range 1–20 μm ∼289 holes/mm2 as well. The may play major role processes within film well on degradation solar cells. This is further confirmed rapid decreasing efficiency perovskite cells solution prepared layers when exposed air.