Nickel Oxide Hole Transport Layer Research Articles

In Situ Growth of Nickel Oxide Hole-Transport Layer through the Nickel Oleate Route for High-Performance Perovskite Solar Cells

In Situ Growth of Nickel Oxide Hole-Transport Layer through the Nickel Oleate Route for High-Performance Perovskite Solar Cells

Improving the Optoelectrical Properties of a Nickel Oxide Hole Transport Layer by Hydrogen Peroxide Treatment for Efficient Organic Solar Cells

Improving the Optoelectrical Properties of a Nickel Oxide Hole Transport Layer by Hydrogen Peroxide Treatment for Efficient Organic Solar Cells

Critical role of dopant in NiOx hole transport layer for mitigating redox reactivity at NiOx/absorber interface in mixed cation perovskite solar cells.

Redox chemistry transpiring at the interface of NiOx hole transport layer (HTL) and perovskite absorber is a critical phenomenon leading to relatively low values of open circuit voltage (VOC) and fill factor (FF), in turn hampering the overall device performance and stability. In this work, for the first time, the hard acid electronic nature of vanadium (V) dopant in nickel oxide HTL is opportunely exploited to mitigate the undesirable Lewis acid-base reactions occurring at the HTL/mixed-cation perovskite interface. The findings of the study show that vanadium doping results in improved interfacial energetics along with decreased VOC loss, confirming that despite the increase in Ni3+/Ni2+ ratio with the vanadium dopant, the redox reaction catalyzed by Ni3+ ions is kept under check. Vanadium doping also aided in the realization of superior perovskite films with lower Urbach energy, which translated into one order increase in maximum photoinduced carrier generation rate per unit volume. Carrier dynamics investigations show fewer defect states (lower VTFL) and trap-assisted recombination (lower diode ideality factor), which optimize the devices' photovoltaic performance. These benefits collectively contribute to low-loss charge transfer across the NiOx/mixed-cation perovskite interface, which increases the relative efficiency by ∼30% for 5 wt% V-doped NiOx devices compared to pristine NiOx devices, augmented by an increase in device J-V parameters like open circuit voltage (VOC), short circuit current density (JSC), and fill factor (FF).

Buried-Interface Engineering Enables Efficient and 1960-HourISOS-L-2I Stable Inverted Perovskite Solar Cells.

High-performance perovskite solar cells (PSCs) typically require interfacial passivation, yet this is challenging for the buried interface, owing to the dissolution of passivation agents during the deposition of perovskites. Here, this limitation is overcome with in situ buried-interface passivation-achieved via directly adding a cyanoacrylic-acid-based molecular additive, namely BT-T, into the perovskite precursor solution. Classical and ab initio molecular dynamics simulations reveal that BT-T spontaneously may self-assemble at the buried interface during the formation of the perovskite layer on a nickel oxide hole-transporting layer. The preferential buried-interface passivation results in facilitated hole transfer and suppressed charge recombination. In addition, residual BT-T molecules in the perovskite layer enhance its stability and homogeneity. A power-conversion efficiency (PCE) of 23.48% for 1.0cm2 inverted-structure PSCs is reported. The encapsulated PSC retains 95.4% of its initial PCE following 1960h maximum-power-point tracking under continuous light illumination at 65°C (i.e., ISOS-L-2I protocol). The demonstration of operating-stable PSCs under accelerated ageing conditions represents a step closer to the commercialization of this emerging technology.

Design of an eco-friendly perovskite Au/NiO/FASnI3/ZnO0.25S0.75/FTO, device structure for solar cell applications using SCAPS-1D

Formamidinium Tin Iodide (FASnI3) based perovskite solar cells (PSC) have captured the interest of scientific community because of wide bandgap and good thermal stability, but limited power conversion efficiency (PCE) restricts their extensive adaptation. Here, we present the design of a FASnI3 active layer-based PSC with Nickel oxide (NiO) as Hole Transport Layer (HTL) & Zinc Oxy-Sulphide (ZnO0.25S0.75) as the Electron Transport Layer (ETL). The proposed Au/NiO/FASnI3/ZnO0.25S0.75/FTO, device structure is investigated using SCAPS-1D solar cell capacitance simulator. The performance parameters of proposed solar cells device structure are investigated with variations in active layer (FASnI3) thickness, defect density & doping concentration; and variations of NiO HTL & ZnO0.25S0.75 ETL thickness, electron affinity & doping concentration to obtain higher performance. Moreover, the influence of series & shunt resistance, and temperature on the performance parameters of proposed solar cell device structure is inspected. The proposed Au/NiO/FASnI3/ZnO0.25S0.75/FTO, device structure revealed excellent solar cell performance parameters such as low short-circuit current density (Jsc) of ∼28.35 mA/cm2, high Fill Factor (FF) of ∼89.64%, reasonable open-circuit voltage (Voc) of ∼1.2419 V, & admirable PCE of ∼31.57%, suitable for lead-free and eco-friendly solar cell device applications.

Modeling and Simulation of Tin Sulfide (SnS)-Based Solar Cell Using ZnO as Transparent Conductive Oxide (TCO) and NiO as Hole Transport Layer (HTL).

This paper describes the simulation by Solar Cell Capacitance Simulator-1D (SCAPS-1D) software of ZnO/CdS/SnS/NiO/Au solar cells, in which zinc oxide (ZnO) is used as transparent conductive oxide (TCO) and nickel oxide (NiO) is used as a hole transport layer (HTL). The effects of absorber layer (SnS) thickness, carrier concentration, SnS defect density, NiO HTL, ZnO TCO, electron affinity and work function on cell performance have been evaluated. The effect of interface defect density of SnS/CdS on the performance of the heterojunction solar cell is also analysed. As the results indicate, a maximum power conversion efficiency of 26.92% was obtained.

Temperature optimization of NiO hole transport layer prepared by atomic layer deposition

Atomic layer deposited (ALD) nickel oxide (NiO) thin film is frequently utilized as a hole transport layer (HTL) for perovskite solar cells (PSCs). Particularly nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)2) precursor and ozone reactant are used for NiO film deposition. The substrate temperature effect on the stoichiometric composition for oxygen vacancies defects and electrical properties such as mobility is crucial, affecting further device performance. In the present study, NiO thin films are grown using the ALD method at a substrate temperature range between 180 to 250 °C on SiO2/Si substrates. Next, the effect of substrate temperature on the film composition, valence levels, nickel oxidation states, oxygen vacancies, and electrical properties was systematically examined, not to mention film growth, thickness, morphology, crystallinity, and optical properties. At 180 °C, the film growth rate was 0.017 nm/cycle, which was increased to 0.025 nm/cycle at 250 °C. All grown NiO films exhibited polycrystalline cubic crystal orientation, and the (200) plane simultaneously Ni3+ phase coexists with the Ni2+ phase. Furthermore, the electrical resistivity and mobility increased from 2.36 – 3.24 × 102 Ω.cm and 9.6–21.9 cm2V−1s−1 with substrate temperatures of 180 °C–230 °C. The prepared NiO films were optically transparent, >70% in the visible region, and the Ultraviolet photoelectron spectroscopy (UPS) study revealed that the variation in the valance band and conduction bands critically depended on the growth temperature. Thus, our findings reveal that the chemical and electrical characteristics of deposited NiO thin film are precisely influenced by substrate temperature; it will also offer considerable promise for developing NiO HTL concerning PSCs device improvement.

Influence of annealing temperature of nickel oxide as hole transport layer applied for inverted perovskite solar cells

Nickel oxide (NiO) has recently attracted great attention for its use as a hole transport layer (HTL) of inverted perovskite solar cells (PSCs). In this paper, NiO films are fabricated on a silicon wafer and fluorine-doped tin oxide by plasma-enhanced atomic layer deposition (PEALD) with nickelocene as the metal precursor and oxygen plasma as the coreactant. The effects of the annealing treatment on the film properties at different annealing temperatures are analyzed. The experimental results show that the PEALD-NiO films have a high thickness uniformity and low surface roughness as evaluated by atomic force microscopy measurements. All the PEALD-NiO films have a wide bandgap and high transmittance of ∼80%–85% in the visible light range. The postannealing treatment induces a reduced electrical resistivity owing to crystal structure repair and surface defect reduction. This treatment also leads to a significantly enhanced wettability of the NiO films, facilitating perovskite layer deposition in subsequent device fabrication. Finally, the inverted PSCs based on the NiO HTL with different annealing temperatures demonstrate an enhanced performance of the device as compared to that with unannealed NiO HTL. The 400 °C-annealed PEALD-NiO HTL yields the best cell conversion efficiency, improving from 15.38% for unannealed NiO to 17.31%, demonstrating the potential of PEALD-NiO compact films for applications in inverted PSCs.

A Hybrid Hole Transport Layer for Perovskite-Based Solar Cells

This paper presents the effect of a composite poly(3,4-ethylenedioxythiophene) polystyrene sulfonate PEDOT:PSS and copper-doped nickel oxide (Cu:NiOx) hole transport layer (HTL) on the performance of perovskite solar cells (PSCs). Thin films of Cu:NiOx were spin-coated onto fluorine-doped tin oxide (FTO) glass substrates using a blend of nickel acetate tetrahydrate, 2-methoxyethanol and monoethanolamine (MEA) and copper acetate monohydrate. The prepared solution was stirred at 65 °C for 4 h and spin-coated onto the FTO substrates at 3000 rpm for 30 s in a nitrogen glovebox. The Cu:NiOx/FTO/glass structure was then annealed in air at 400 °C for 30 min. A mixture of PEDOT:PSS and isopropyl alcohol (IPA) (in 1:0.05 wt%) was spun onto the Cu:NiOx/FTO/glass substrate at 4000 rpm for 60 s. The multilayer structure was annealed at 130 °C for 15 min. Subsequently, the perovskite precursor (0.95 M) of methylammonium iodide (MAI) to lead acetate trihydrate (Pb(OAc)2·3H2O) was spin-coated at 4000 rpm for 200 s and thermally annealed at 80 °C for 12 min. The inverted planar perovskite solar cells were then fabricated by the deposition of a photoactive layer (CH3NH3PbI3), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and a Ag electrode. The mechanical behavior of the device during the fabrication of the Cu:NiOx HTL was modeled with finite element simulations using Abaqus/Complete Abaqus Environment CAE. The results show that incorporating Cu:NiOx into the PSC device improves its density–voltage (J–V) behavior, giving an enhanced photoconversion efficiency (PCE) of ~12.8% from ~9.8% and ~11.5% when PEDOT:PSS-only and Cu:NiOx-only are fabricated, respectively. The short circuit current density Jsc for the 0.1 M Cu:NiOx and 0.2 M Cu:NiOx-based devices increased by 18% and 9%, respectively, due to the increase in the electrical conductivity of the Cu:NiOx which provides room for more charges to be extracted out of the absorber layer. The increases in the PCEs were due to the copper-doped nickel oxide blend with the PEDOT:PSS which enhanced the exciton density and charge transport efficiency leading to higher electrical conductivity. The results indicate that the devices with the copper-doped nickel oxide hole transport layer (HTL) are slower to degrade compared with the PEDOT:PSS-only-based HTL. The finite element analyses show that the Cu:NiOx layer would not extensively deform the device, leading to improved stability and enhanced performance. The implications of the results are discussed for the design of low-temperature solution-processed PSCs with copper-doped nickel oxide composite HTLs.

A numerical simulation of high efficiency CdS/CdTe based solar cell using NiO HTL and ZnO TCO

Simulation of cadmium sulfide (CdS) and cadmium telluride (CdTe) based solar cell (ZnO/CdS/CdTe/NiO/Au) using Solar Cell Capacitance Simulator-1D (SCAPS-1D) has been presented in this article. Nickel oxide (NiO) and zinc oxide (ZnO) layers have been introduced as hole transport layer (HTL) and transparent conductive oxide (TCO), respectively. ZnO, CdS, and CdTe were synthesized using the facile chemical route, and their absorption coefficient was determined systematically. Later these experimentally found absorption coefficient data were used to study the effect of NiO HTL and ZnO TCO on the performance of CdS/CdTe based solar cell using SCAPS-1D. The impact of thickness, carrier concentration, defect density of the CdTe, and CdS/CdTe interface defect density on the solar cell performance was also investigated. The optimized solar cell demonstrated a maximum power conversion efficiency (PCE) of 28.04 % with open circuit voltage (VOC) of 1.09 V, short circuit current density (JSC) of 29.09 mA/cm2 and FF of 87.84 % that shows huge promise in low-cost solar energy harvesting.

High-efficiency perovskite solar cell using cobalt doped nickel oxide hole transport layer fabricated by NIR process

Lead halide perovskite solar cells (PVSCs) have potential toward commercialization because of their high efficiency and low cost. The hole transport layer (HTL) of p-i-n perovskite solar cell is usually made of NiOX. However, the NiOX needs to be processed at 300 °C for 15 min for good hole transport property. This long heating time prohibits the development of continuous commercial process. Thus, a rapid heating process for the NiOX film deposition is critical to realize the commercialization of PVSCs in the future. In this study, we develop a facile method to obtain high quality NiOX films annealed by NIR in a short time of 50 s. A short-wave NIR lamp at 2500 K was used to systematically investigate the effect of NIR intensity on the film quality of sol-gel NiOX. The PVSCs fabricated from NIR-annealed NiOX (NIR-NiOX) film show a comparable power conversion efficiency (PCE) to those fabricated from traditional hot-plate annealed-NiOX (HP-NiOX). In addition, the NIR annealed cobalt-doped NiOX (NIR-Co:NiOX) was synthesized to replace pristine NIR-NiOX. The PCE of PVSCs fabricated from this new NiOX film can be increased from 15.99% to 17.77%, which is due to the efficient hole extraction, less charge accumulation, and reducing Voc loss resulting from the improved hole mobility, reduced interface resistance and well-matched work function. Our study paves a way to fulfill the requirements of low cost and low energy consumption of large scale production of high efficiency PVSCs.

Fine modification of reactively sputtered NiOX hole transport layer for application in all-inorganic CsPbI2Br perovskite solar cells

In this study, nickel oxide (NiOX) thin films were prepared by direct current (DC) reactive magnetron sputtering. The various properties of NiOX thin films including deposition rate, morphology, electrical and optical properties as well as grain structure and chemical composition were systematically investigated. The material properties of NiOX were finely modified under the monitoring of target voltage during sputtering. NiOX thin films were applied as hole transport layers (HTLs) in all-inorganic CsPbI2Br perovskite solar cells (PSCs). The highest efficiency of 12.6% had been achieved for the optimized all-inorganic CsPbI2Br PSCs with the inverted structure of Glass/FTO/NiOX(HTL)/CsPbI2Br/ZnO@C60 (electron transport layer, ETL)/Ag. The PSC still yielded over 90% of its initial power output after 10 h operation without encapsulation.

Thermal oxidation of sputtered nickel nano-film as hole transport layer for high performance perovskite solar cells

The effect of rapid oxidation temperature on the sputtered nickel (Ni) films to act as a hole transport layer (HTL) for perovskite solar cell (PSCs) was investigated. A nano-sputtered Ni film with a thickness about 100 nm was oxidized at a range of different oxidation temperatures between 350 and 650 °C to work as HTL in an inverted p–i–n configuration. DC Hall measurement in van der Pauw configuration and photoluminescence spectroscopy were used to measure the charge’s mobility and extraction of nickel oxide (NiO) films. The behaviour of the carrier concentration measurements of NiO layers at different oxidation temperatures showed that the Ni layer oxidized at 450 °C had the highest carrier concentration among the other samples. The performance measurements of the fabricated PSCs showed that the nickel oxide hole-transporting layer which has been oxidized at the optimum oxidation temperature of 450 °C has the highest power conversion efficiency (PCE) of 12.05%. Moreover, the characteristic parameters of the optimum cell such as the open-circuit voltage (VOC), short-circuit current density (JSC) and fill factor (FF) were 0.92 V, 19.80 mA/cm2 and 0.331, respectively.

Large-Area Organic-Free Perovskite Solar Cells with High Thermal Stability.

Organic-free perovskite solar cells (PSCs) have been considered as the most promising candidate for achieving long-term stability. Here, we demonstrate an organic-free PSC consisting of inorganic CsPbI2Br perovskite, nickel oxide hole transport layer, and niobium oxide electron transport layer. A maximum power conversion efficiency (PCE) of 11.20% is achieved with an active area of 5 cm2, and it increases to 14.11% with smaller area. More importantly, the organic-free PSCs show excellent thermal stability with PCE remaining above 98% of its initial value when heated at 100 °C for 150 min. Postannealing at a proper temperature further increases its maximum PCE to 14.45%, which is the highest among any reported all-inorganic PSCs with a p-i-n structure. The enhanced performance of the postannealed device is ascribed to the decreased trap-state density and improved interface charge-transfer properties. These results demonstrated that this novel organic-free device architecture can be employed to fabricate efficient and stable PSCs for large-scale manufacturing.

Investigation of sol-gel and nanoparticle-based NiOx hole transporting layer for high-performance planar perovskite solar cells

We conduct a comprehensive study on and comparison of sol-gel and nanoparticles (NPs)-based nickel oxide hole-transporting layer (HTL) for high-performance planar perovskite solar cells (PSCs). The characteristics and film properties of sol-gel and NPs were systemically investigated using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and photoluminescence (PL), and its effect on device-performance was also examined using J-V characteristics, quantum-efficiency, and the VOC dependence of the light intensity. Through this comparison of two types of HTL and their device-performances, these studies can provide sufficient and robust information for nickel oxide-based PSCs, and furthermore, the overall results and discussions can be useful for high-performance PSCs.

High-performance inverted planar perovskite solar cells based on solution-processed rubidium-doped nickel oxide hole-transporting layer

Abstract Organic–inorganic hybrid perovskite solar cells (PVSCs) have attracted great attention due to the high power conversion efficiency (PCE). For the p-i-n inverted structure PVSCs, the hole transporting layer (HTL) plays an important role in achieving high efficient and stable PVSCs by improving charge extraction, reducing interfacial recombination, and modifying band alignment etc. In this work, rubidium (Rb) doped NiOx (Rb:NiOx) was employed as HTL to study the impacts on the optoelectronic properties and the photovoltaic performance. Both NiOx and Rb:NiOx films were smooth and highly transparent with a simple solution-based method. The Rb:NiOx films exhibited better conductivity and effectively elevated the valence band maximum (VBM). At the same time, the Rb doping induced a better morphology of perovskite film with larger crystals size on top. Therefore, Rb doping resulted in significantly improved hole extraction and reduced recombination losses. As a result, the photovoltaic performance of the PVSCs was remarkably increased from 14.48% to 17.21%.

Large-Area Organic-Free Perovskite Solar Cells with High Thermal Stability

Organic-free perovskite solar cells (PSCs) with all inorganic functional layers have been considered as the most promising candidate for achieving long-term stability. Here, we demonstrate the first organic-free PSC consisted of inorganic CsPbI2Br perovskite, nickel oxide hole transport layer, and niobium oxide electron transport layer. The as-fabricated organic-free PSC exhibits a maximum PCE of 11.20% with a large active area of 5 cm2. The PCE is increased to 14.11% with smaller area and retains above 98% of its initial value after being stored in nitrogen atmosphere for 30 days. More importantly, the organic-free PSCs show excellent thermal stability with PCE remained above 98% of its initial value after being heated at 100 °C for 150 min. The high thermal stability of the device makes it possible to conduct post-annealing to further increase its maximum PCE to 14.45%, which is the highest among any reported all-inorganic PSCs with p-i-n structure. The enhanced performance of the post-annealed device is ascribed to the decreased trap-state density and improved interface charge transfer properties of the device. These results demonstrated that this novel organic-free device architecture can be employed to fabricate efficient and stable PSCs for large-scale manufacturing.

A solution-processed cobalt-doped nickel oxide for high efficiency inverted type perovskite solar cells

Optimal interfaces play an important role in determining the efficiency of perovskite solar cells. Despite nickel oxide is a promising hole transport material in perovskite solar cells, electrical conductivity and surface properties of pristine nickel oxide are not satisfactory for achieving high efficiency perovskite solar cells. Here, we demonstrate that cobalt doping significantly improves not only the electrical conductivity but also the interfaces of nickel oxide hole transport layer. As a result, the hole extraction, transport and collection properties are significantly improved in the device using cobalt-doped nickel oxide as a hole transport layer. Also, it reveals that cobalt-doped nickel oxide reduces the trap-sites of interfaces of perovskite/hole transport layer, leading to suppressed charge recombination in the devices. As a result, the devices using cobalt-doped nickel oxide achieve as high as 17.52% without severe hysteresis, which is attributed to better band alignment, superior hole extraction and decreased resistance, as compared to pristine nickel oxide-based devices.

Lithium and Silver Co-Doped Nickel Oxide Hole-Transporting Layer Boosting the Efficiency and Stability of Inverted Planar Perovskite Solar Cells.

In this work, a lithium and silver co-doping strategy has been successfully implied to prepare NiO x films for high performance inverted planar perovskite solar cells (PSCs). Compared to the pristine and single-doped NiO x, the Li and Ag co-doping approach exhibits the synergistic effect and can endow NiO x films with higher electrical conductivity, higher hole mobility and better interface energy band alignment with perovskite active layers. Moreover, the perovskite film with enhanced crystallinity can be obtained induced by the Li,Ag:NiO x film. The PSC with Li,Ag:NiO x HTL shows a high power conversion efficiency (PCE) up to 19.24% and less hysteresis effect, which outperforms the devices with the pristine NiO x or single-doped NiO x HTLs. Meanwhile, the Li,Ag:NiO x device can retain 95% of its initial PCE after storage at the relative humidity of 30 ± 2% in 30 days without encapsulation. Our work demonstrates that lithium and silver co-doping is a promising route for realizing efficient p-type NiO x HTL, which provides a simple way to boost the efficient and stable of inverted planar PSCs.

(Invited) Engineering of Nickel Oxide Hole Transport Layer for Inverted Perovskite Solar Cells

Introduction The NiOx layer is actively used as hole extraction layer for inverted structure perovskite solar cells. However, clear guidelines on NiOx chemical composition, manufacturing methods, energy levels, and the hole-transport process remain unclear. In this conference, high-density NiOx layers with various manufacturing temperatures are produced with Nickel acetylacetonate using the SPD method in order to improve the performances of inverted perovskite solar cells. The chemical composition of the NiOx is investigated using XPS, and GIXRD. Furthermore, the influence of Na+ ions in the valence band of the NiOx layer is investigated by vacuum ultraviolet photoelectron spectroscopy using synchrotron radiation. The results showed that the conversion efficiency of the perovskite solar cell is high as the crystallite size of NiOx is large. The highest perovskite solar cell conversion efficiency was obtained at a NiOx layer production temperature of 550 °C. Inverted perovskite solar cells were fabricated with over 16.1% conversion efficiency. Conversion efficiency of solar cell The conversion efficiencies of the perovskite solar cells using NiOx films with various deposition temperatures are summarized in Table 1. The perovskite solar cells conversion efficiency increased along with the NiOx layer production temperature to 550 and 600 °C; however, it decreased slightly when the temperature increased further to 600 °C. As a result, the perovskite solar cell conversion efficiency reached its peak when the NiOx layer production temperature was 500 °C. To highlight the performance change, we herein investigated the composition, structure and the band state of the NiOx layers. Influence of valence band and valence of Ni ion of the NiOx layers To investigate the states of the regions near the edges of the valence bands of the NiOx layers, PES measurements were carried out with a BL-07B at the NewSUBARU synchrotron radiation facility, and the results are shown in Figure 1. The regions near the edges of the valence bands of the NiOx correspond to Ni 3d (label A), O 2p (label B), and the charge transfer transition from an O 2p level to Ni 3d photoionization (label C). From the PES measurement results, the region (around 4-5 eV) corresponding to O 2p was stronger at 300 and 600 °C than at 500 °C. This is because the influence of the O 2p orbital increased because the proportion of oxygen in NiOx increased owing to the loss of Ni ions. Although the ratio of Ni2+ to Ni3+ ions affects the energy levels in the vicinity of the HOMO, a change in these energy levels does not contribute to hole extraction in perovskite solar cells. From these results, it was found that the valence of the Ni ions has little influence on the performance of the solar cells. Crystal analysis of the NiOx layers Both the structures and crystallite sizes of the thin NiOx films formed by SPD were investigated via GIXRD, as shown in Figure 2. The five peaks that appeared at 2θ values of approximately 37.6° 43.6°, 63.3°, 75.6°, and 79.6° were assigned to the 111, 200, 220, 311, and 222 planes, respectively, and then attributed to the randomly oriented NiOx crystal. At 250 °C, no diffraction peaks were observed because the NiOx film did not crystallise. This implies that crystallised NiOx films formed with annealing temperatures above 300 °C. The NiOx crystallite sizes were calculated from the intensities of the 200 peaks using the Scherrer equation, and the results are shown in Figure 1, which indicates that their sizes increased with increasing SPD temperatures. The size of a NiOx crystallite and the tendency of conversion efficiency were consistent, except at 550 and 600 °C, where the FTO layer broke beyond the glass transition point. In other words, as a guideline for manufacturing high-performance inverted perovskite solar cells, it is important to enlarge the crystallites in the NiOx film. Conclusions We demonstrated that it is related to the NiOx crystallite size and the conversion efficiency of the perovskite solar cells, which can be used as a guideline to achieve high performance. The highest perovskite solar cell conversion efficiency was obtained at a NiOx layer production temperature of 500 °C. In the inverse perovskite solar cell, the conversion efficiency exceeded 16.1%, and hysteresis was not observed. Moreover, the measurements of the valence band using synchrotron radiation indicated that the ratio of Ni2+ to Ni+3 had little effect on the solar cell performance. This is an important guideline for improving the performance of perovskite solar cells. Acknowledgement This work was supported by New energy and industrial Technology Development Organization (NEDO), Japan.