Managing the Double-Edged Sword of Ni³⁺ in Sputter-Deposited NiO_x by Interfacial Redox Reactions for Efficient Perovskite Solar Cells

Abstract

Nickel oxide (NiO x ) is widely used as a promising hole transport material for perovskite solar cells (PSCs). A high concentration of Ni 3+ in the NiO x film is generally beneficial for charge transport of the PSCs; however, chemical redox reactions between surface Ni 3+ and perovskite materials result in decomposition of perovskite materials, which causes carrier recombination and impedes charge transport at the perovskite−NiO x interface. Herein, we employ magnetron sputtering to fabricate NiO x thin films with adjustable Ni 3+ concentrations to optimize the hole-transporting properties. A thin layer of phenylethylamine iodide (PEAI) is further introduced to reduce the detrimental Ni 3+ at the surface of NiO x , which eliminates the formation of undesirable defects and chemical species when in contact with the perovskite layer, leading to a dramatic increase in the power conversion efficiency (PCE) from 16.37 to 20.01%, which is one of the best performance using sputtered charge transport layers. The unencapsulated devices retain 88% of their initial PCE after storage in a nitrogen atmosphere for 1000 h under light. We further perform solar cell capacitance simulator (SCAPS) simulation to understand the effects of bulk and interfacial charge transport on the performance of PSCs, which agree with our experimental results. This work not only highlights the double-edged sword effect of the Ni 3+ content on the performance and stability of PSCs but also demonstrates a simple yet effective strategy to avoid the undesirable reaction between Ni 3+ and perovskite materials in the fabrication of PSCs with sputter-deposited NiO x .

Perovskite Solar Cells with All Functional Layers Deposited by Magnetron Sputtering

“…Then, sp-SnO 2 and Ag electrodes were deposited sequentially on top of the sputtering buffer layer using magnetron sputtering (Figure 1a). Based on a previous work, 29 the device energy band structure is shown in Figure 1b. This all-inorganic-CTL device has a matched energy band structure, which is conducive for building a built-in electric field and charge extraction.…”

“…are ionized and accelerated in an electric field, and then the high-energy Ar + exchanges momentum with the target surface atoms so that the target atoms have enough kinetic energy to break away from the target and deposit on the substrate. , Compared to other vapor deposition techniques, magnetron sputtering has the advantages of a fast deposition speed, dense and adhesive film formation, and relatively low requirements for equipment vacuum degree, making it a relatively robust deposition technique. , At the same time, due to its working principle of momentum exchange, the material selection of magnetron sputtering is wide and it can be applied to the deposition of most metals and oxide ceramics. It is worth noting that all functional layers in PSCs can be deposited by magnetron sputtering. − Replacing the organic CTL with a sputtered inorganic CTL can also reduce cost and improve stability. However, the principle of magnetron sputtering determines that both the magnetron sputtering deposition of perovskite layers and the subsequent deposition of other films on perovskite layers will damage the soft lattice perovskite materials.…”

Understanding and Mitigating the Degradation of Perovskite Solar Cells Based on a Nickel Oxide Hole Transport Material during Damp Heat Testing

“…47,48,12,49 Peng et al demonstrated that a passivation of the NiO x surface is required to decrease Ni 3+ concentration at the NiO x /perovskite interface and avoid redox reaction between I − from the perovskite and Ni 3+ from the NiO x . 50 The main advantage of employing NiO x as HTM lies in the film uniformity and high yield of working devices (i.e., not shunted) when scaling the fabrication to larger cells (>1 cm 2 ) and modules compared to organic HTMs, which are typically only a few nanometers thick and thus more prone to pinholes. Prior to device fabrication, the RF-sputtered NiO x layer was annealed in air at 300 °C for 15 min.…”

“…Boyd et al showed that a redox reaction occurs at the interface between NiO x and perovskites, with the formation of an A-site deficient lead bromide/iodide phase at the surface, which accelerates interfacial recombination, thus reducing the V OC of the cells. Several studies attribute the limited V OC that is achievable with NiO x to nonradiative recombination at the perovskite interface with the HTM. ,,, Peng et al demonstrated that a passivation of the NiO x surface is required to decrease Ni 3+ concentration at the NiO x /perovskite interface and avoid redox reaction between I – from the perovskite and Ni 3+ from the NiO x …”

Isolating the Oxygen Adsorption Defects on Sputtered Tin Oxide for Efficient Perovskite Solar Cells

“…Different from the solution method, which is mainstream in the laboratory, magnetron sputtering is one of the most mature film deposition techniques in industry , with many advantages such as a fast deposition speed, uniform and dense film formation, solvent-free deposition process, and low vacuum degree requirements for the equipment. All functional layers of PSCs can be deposited by magnetron sputtering. ,− All these advantages make magnetron sputtering an attractive option for future industrial production.…”