High-Efficiency and Stable Inverted Planar Perovskite Solar Cells with Pulsed Laser Deposited Cu-Doped NiO_x Hole-Transport Layers

Abstract

High-quality hole-transport layers (HTLs) with excellent optical and electrical properties play a significant role in achieving high-efficient and stable inverted planar perovskite solar cells (PSCs). In this work, the optoelectronic properties of Cu-doped NiO x (Cu:NiO x ) films and the photovoltaic performance of PSCs with Cu:NiO x HTLs were systematically studied. The Cu-doped NiO x with different doping concentrations was achieved by a high-temperature solid-state reaction, and Cu:NiO x films were prepared by pulsed laser deposition (PLD). Cu+ ion dopants not only occupy the Ni vacancy sites to improve the crystallization quality and increase the hole mobility, but also substitute lattice Ni2+ sites and act as acceptors to enhance the hole concentration. As compared to the undoped NiO x films, the Cu:NiO x films exhibit a higher electrical conductivity with a faster charge transportation and extraction for PSCs. By employing the prepared Cu:NiO x films as HTLs for the PSCs, a high photocurrent density of 23.17 mA/cm2 and a high power conversion efficiency of 20.41% are obtained, which are superior to those with physical vapor deposited NiO x HTLs. Meanwhile, the PSC devices show a negligible hysteresis behavior and a long-term air-stability, even without any encapsulation. The results demonstrate that pulsed laser deposited Cu-doped NiO x film is a promising HTL for realizing high-performance and air-stable PSCs.

Synthesis of Cu‐Modified Nickel Oxide Nanocrystals and Their Applications as Hole‐Injection layers for Quantum‐Dot Light‐Emitting Diodes

“…The Tauc plots (Figure 2c) indicate that the optical bandgap of oxide nanocrystals slightly narrowed from 3.88 eV to 3.85 eV by Cu‐modification, which is similar to previously reported Cu‐doped NiO x films [37,38] . Kelvin probe measurements shown in Figure 2d reveal that the surface Cu‐modification step does not change the work function of the oxide nanocrystal films (∼5.4 eV).…”

“…As shown below, initial attempts of applying the as‐prepared NiO x nanocrystals to prepare HILs for QLEDs indicated that the electrical conductivity of the oxide‐nanocrystal films required significant improvements, which is in accordance with the reported results of pure NiO x generally exhibits a low intrinsic conductivity [11,20,22,35] . In literature, copper doping has been demonstrated to be effective for improving the conductivity of the precursor‐derived NiO x thin films [11,35–39] . In this regard, we developed a simple surface‐modification strategy to enable the anchoring of the Cu species onto the surfaces of the as‐prepared NiO x nanocrystals, resulting in NiO x ‐Cu nanocrystals.…”

Nickel Oxide for Perovskite Photovoltaic Cells

“…The research works of transition metal doping in NiO x are almost exclusively dominated by the p‐type dopants like Co and Cu. [ 96,97 ] Nevertheless, some other elements such as Fe, Zn, Ag, and Al have also been attempted. [ 98–101 ] Chen et al improved the carrier mobility of NiO x by adding Cu, consequently increasing its conductivity significantly, verified by the conductive AFM (c‐AFM) and I − V analysis ( Figure a‐c).…”

“…Subsequently, Feng et al studied the influence of Cu doping concentration on NiO x for PSCs. [ 97 ] The Cu doping did not change the surface morphology significantly, but it reduced the surface roughness (Figure 12e,f), which could be beneficial for the pinhole‐free and smooth surface formation. Cu‐doped NiO x HTL‐based PSCs achieved the highest PCE of 20.41% with J sc of 23.17 mA cm −2 , as shown in Figure 12g.…”

Synergistic Effect of Codoped Nickel Oxide Hole–Transporting Layers for Highly Efficient Inverted Perovskite Solar Cells

“…[10,11] However, the low conductivity and carrier mobility of NiO x films is a substantial drawback, leading to hole accumulation near the perovskite interface, increasing the possibility of recombination, and hindering charge collection. Therefore, numerous methods have been proposed to improve the conductivity and hole extraction of NiO x films, including stoichiometry adjustments, surface treatments, doping with various atoms such as Li, Cu, Ag, Co, Cs, or K, or codoping with Li:Cu or Li:Mg. [12][13][14][15][16][17][18] In particular, in the case of the study involving Li: Cu:NiO x , the effect of each dopant on the NiO x film and their synergetic effect on the film were insufficiently reported; in addition, a low efficiency was reported, with an insufficient explanation of the relationship between the properties of the doped HTL and the perovskite-based device. [14] Herein, we systematically investigated NiO x codoping with Li and Cu dopants to explore the synergistic effect of codoping on the different NiO x HTLs and perovskite PVs.…”