Low temperature processed NiOx hole transport layers for efficient polymer solar cells

Abstract

We here demonstrate the use of solution processed NiO x thin films as the hole transport layer (HTL) in a thiophene-quinoxaline copolymer:fullerene solar cell. The NiO x films, which are prepared by UV-ozone treating a nickel formate precursor, outperform the solar cells prepared in this study that use PEDOT:PSS as HTL. The power conversion efficiency improves from 5.3% to 6.1% when replacing PEDOT:PSS with NiO x . Unlike most conventional ways of fabricating solution processed NiO x HTLs, our method does not require high temperature (>300°C). In fact, we were able to produce high performing NiO x HTLs without the use of any thermal annealing. X-ray photoelectron spectroscopy revealed that a mixture of oxides and hydroxides is formed as a result of the UV-ozone treatment, which differs in composition from those formed by high temperature annealing; UV-ozone treatment produces NiOOH, while only the high temperature annealing produces any significant amount of NiO. Contact

18.77 % Efficiency Organic Solar Cells Promoted by Aqueous Solution Processed Cobalt(II) Acetate Hole Transporting Layer

“…However, the high‐temperature TA process suffers from high energy cost and is not compatible with flexible devices because general flexible substrates like polyethylene terephthalate (PET) are not able to withstand high‐temperature TA process above 150 °C [18] . Only few metal oxides could be prepared from their precursor solution at low temperature by a post decomposition in the presence of H 2 O 2 or UV‐ozone (UVO) treatment [10d, 11b, 13, 14] . Alterative to the metal oxides, some metal salts has also been applied as HTLs, such as cuprous iodide (CuI) [19] and cuprous thiocyanate (CuSCN) [20] .…”

Nickel oxide thin films grown by chemical deposition techniques: Potential and challenges in next‐generation rigid and flexible device applications

“…There have been extensive studies on solution‐processed NiO x for organic solar cells, with differing polymer blends for the photoactive layer, different solvents for the NiO x precursor, annealing temperature, and post‐deposition treatments. Work function tuning results in values > 5.0 eV and power conversion efficiencies (PCEs) between 3.6% and 7.8% 102,107,172,178,179 . The band alignment for common organic materials with charge transport layers are shown in Figure 11.…”

“…Work function tuning results in values >5.0 eV and power conversion efficiencies (PCEs) between 3.6% and 7.8%. 102,107,172,178,179 The band alignment for common organic materials with charge transport layers are shown in Figure 11. In addition to solution processing, Shim et al reported the first use of ALD deposited NiO x for polymer solar cells using Ni-AMD (Nickel Alkyl Amidinate) and H 2 O precursor, with a deposition temperature of 150 C. Then, 25 nm films, with a band gap of 3.7 eV, were oxygen plasma treated for 3 minutes following deposition, which increased the work function from 4.7 eV to 5.4 eV with the formation of nickel oxyhydroxide species or nickel vacancies on the surface.…”

18.77 % Efficiency Organic Solar Cells Promoted by Aqueous Solution Processed Cobalt(II) Acetate Hole Transporting Layer

“…However, the high‐temperature TA process suffers from high energy cost and is not compatible with flexible devices because general flexible substrates like polyethylene terephthalate (PET) are not able to withstand high‐temperature TA process above 150 °C [18] . Only few metal oxides could be prepared from their precursor solution at low temperature by a post decomposition in the presence of H 2 O 2 or UV‐ozone (UVO) treatment [10d, 11b, 13, 14] . Alterative to the metal oxides, some metal salts has also been applied as HTLs, such as cuprous iodide (CuI) [19] and cuprous thiocyanate (CuSCN) [20] .…”