Page 95 - Read Online

Kim et al. Soft Sci 2024;4:33 https://dx.doi.org/10.20517/ss.2024.28 Page 19 of 31

Figure 10. Schematic illustration of carrier dynamics in CuI under high and low carrier density conditions. Copyright 2022 Li et al. [120] .
CuI: Copper iodide.

Choudhury et al. investigated nanocrystalline CuI HIL/HTL, which were made using a solution process
dissolved in an ammonia-water solution, followed by low-temperature annealing at 110 °C. The annealed
nanocrystalline CuI layer exhibited higher optical properties, better hole injection capability, and improved
crystallinity compared to the CuI without annealing. A green OLED with the annealed nanocrystalline CuI
-1
showed a maximum EQE (EQE ) of 17%, a maximum power efficiency (PE ) of 64 lu·W , and a CE of
max
max
max
62 cd·A . These values are enhanced by 54%, 33%, and 15%, respectively, compared to a CuI layer without
-1
annealing. They also surpass the general HIL [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate
(PEDOT:PSS)] by 35%, 41%, and 38%, respectively [Figure 11B] . Table 4 indicates the summarized
[128]
properties of CuI HIL OLEDs.
Solar cell
CuI-based HTLs have attracted attention due to their large bandgap, high conductivity, low cost, non-
toxicity, solution processability, and high stability. Typically, PEDOT:PSS, poly[bis(4-phenyl)(2,4,6-
trimethylphenyl)amine] (PTAA), 2,2’,7,7’-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene
(spiro-MeO-TAD), and poly(3-hexylthiophene-2,5-diyl) (P3HT) are used as HTLs for solar cells . Here,
[131]
we discuss various studies on CuI HTLs in organic solar cells, perovskite solar cells, and inverted perovskite
solar cells, and compared their performance with typical HTLs.