Inorganic Hole Research Articles

Synthesis and scalable process for fabrication of Perovskite Solar Cells using organic and inorganic hole transport materials

The Organic Inorganic Lead Iodide perovskite material has emerged as a pioneer in being an active material for third-generation solar cells. Apart from the synthesis, the scalable mechanism which is being used for the deposition process, greatly influences the performance of the cell owing to its impact on the morphology, uniform thickness, and interface between two functional layers. This study briefly discusses the various deposition processes involved in assembling the layers of perovskite solar cells (PSC). Hole transport materials (HTM) are a crucial part of the PSC providing efficient transport of the charge carriers. However, the effect of organic and inorganic HTMs is highly pronounced in the PSCs. This study also discusses the effect of organic and inorganic HTM on the stability and efficiency of the sandwich-structured PSC.

Hierarchical Nanostructures CuBi2O4 Integrated with Polyaniline Nanofibrous for Boosting Hole Extraction in Carbon-Based Perovskite Solar Cells.

Toward commercialization of carbon-based perovskite solar cells (C-PSCs), it is crucial to innovatively design inorganic hole transport layer materials that excel in extracting and transporting charge carriers to promote their photoelectric conversion efficiency (PCE). In this work, a novel and high-connectivity CuBi2O4-polyaniline nanofibrous (CuBi2O4-PN) reticular structure is created by integrating CuBi2O4 hierarchical microspheres (CuBi2O4 MS) with polyaniline nanofibrous. The introduction of CuBi2O4-PN as a hole transport layer (HTL) notably enhances the contact quality of the devices and substantially reduces the surface defects of C-PSCs. In a comparative analysis under identical experimental conditions, MAPbI3 devices incorporating CuBi2O4-PN HTL demonstrated a PCE of 14.79%, achieving a 44.3% increase over the reference device (10.25%). CuBi2O4-treated C-PSCs retained 89.9% of their original PCE after 45 days in storage, and they demonstrated improved stability over a longer time frame. This remarkable improvement in device performance can be attributed to the effective suppression of nonradiative recombination and the enhancement of the carrier transfer process in the device. Additionally, the unique interconnected reticular structure of CuBi2O4-PN provides efficient pathways for hole transfer, significantly contributing to the enhanced efficiency of the device.

Improvement of the Stability of Quantum-Dot Light Emitting Diodes Using Inorganic HfOx Hole Transport Layer.

One of the major challenges in QLED research is improving the stability of the devices. In this study, we fabricated all inorganic quantum-dot light emitting diodes (QLEDs) using hafnium oxide (HfOx) as the hole transport layer (HTL), a material commonly used for insulator. Oxygen vacancies in HfOx create defect states below the Fermi level, providing a pathway for hole injection. The concentration of these oxygen vacancies can be controlled by the annealing temperature. We optimized the all-inorganic QLEDs with HfOx as the HTL by changing the annealing temperature. The optimized QLEDs with HfOx as the HTL showed a maximum luminance and current efficiency of 66,258 cd/m2 and 9.7 cd/A, respectively. The fabricated all-inorganic QLEDs exhibited remarkable stability, particularly when compared to devices using organic materials for the HTL. Under extended storage in ambient conditions, the all-inorganic device demonstrated a significantly enhanced operating lifetime (T50) of 5.5 h, which is 11 times longer than that of QLEDs using an organic HTL. These results indicate that the all-inorganic QLEDs structure, with ITO/MoO3/HfOx/QDs/ZnMgO/Al, exhibits superior stability compared to organic-inorganic hybrid QLEDs.

Organic Light-Emitting Diodes Comprising an Undoped Thermally Activated Delayed Fluorescence Emissive Layer and a Thick Inorganic Perovskite Hole Transport Layer

Organic Light-Emitting Diodes Comprising an Undoped Thermally Activated Delayed Fluorescence Emissive Layer and a Thick Inorganic Perovskite Hole Transport Layer

Interface passivation treatment enables GaAs/CNT heterojunction solar cells over 19 % efficiency

Without interface passivation, few technologies have realized carbon material-based GaAs heterojunction solar cells (HJSCs) with high power conversion efficiency (PCE) and long-term stability. Here, inorganic hole transport materials, such as CuSCN and CuI, were first created to address the issue of interface photo-generated carrier recombination in GaAs/carbon nanotube (CNT) HJSCs. The application of CuSCN and CuI passivation layer enables the PCE of GaAs/CNT HJSCs to be improved from 8.53 % to 17.22 % and 12.48 %, respectively. Furthermore, by employing the multifunctional WO3 film, which can serve simultaneously as a hole-blocking layer and an anti-reflection coating, to construct a collaborative optimization system, the cell performance can be further enhanced to 19.06 % and 15.53 %, respectively. Additionally, their stability has been significantly enhanced to 98.11 % and 111.5 %, respectively, which are much higher than that of the pristine HJSC (8.53 %). Especially, the high quality of Cu+-based passivation layer affords a fill factor (FF) of 80.21 %, which is a record for GaAs-based HJSCs. This work is a breakthrough as it presents a pioneering cross-generational concept for addressing the poor stability performance of carbon materials-based HJSCs.

Co‐Solvent Assisted Optimization of the CuSCN Hole Transport Layer for Enhancing the Efficiency of Ambient Processable Perovskite Solar Cells with Carbon Counter Electrodes

In recent perovskite solar cell (PSC) research, copper(I) thiocyanate (CuSCN) is an emerging inorganic hole transport layer (HTL) due to its suitable band gap, matched band edge positions with the perovskite and high stability under ambient conditions. However, being a coordination polymer typically requires sulfide‐based solvents that strongly interact with Cu(I) for dissolution. Dipropyl sulfide (DPS) is generally used where it is very sparingly soluble of about 10–12 mg mL−1, which leads to low surface coverage with pin‐holes on the surface responsible for the generation of defects at the perovskite–HTL interface. In this study, addition of the optimized amount 100 μL of co‐solvent Acetonitrile (ACN) increased the CuSCN dissolution from 10 to 35 mg mL−1. ACN can act as a Lewis‐base making it capable of donating electrons to a Lewis‐acid like Cu+ from CuSCN. ACN is a polar aprotic solvent due to its highly polar CN bond and by adding CuSCN the dipole–dipole interactions can stabilize the CuSCN molecules in solution. The device with architecture (FTO/c‐TiO2/mp‐TiO2/MAPbI3/CuSCN/carbon) showed the higher power conversion efficiency (PCE) of ≈11% with Voc of 1.01 V and Isc 24.65 mA cm−2 showing excellent stability stored under ambient atmosphere which retains 80% of its initial efficiency after 10 days.

Enhanced carbon-based back contact electrodes for perovskite solar cells: Effect of carbon paste composition on performance and stability

To address the issue of cost and instability in perovskite solar cells (PSCs), it is promising to substitute the regular hole collecting electrode i.e., spiro-OMeTAD/Au with inorganic hole transport layer (HTL)/carbon electrode. In this study, three carbon pastes were investigated with different binders: polymethyl methacrylate (PMMA), styrene-butadiene-styrene (SBS) and ethyl cellulose (EC). Carbon layers were compared in terms of mechanical stability, conductivity and performance as back contact electrodes in PSCs with an inorganic HTM composed of CuInS2 nanoparticles. To assess mechanical properties of the carbon pastes, adhesion tests by using tape, ultrasonication in the media of deionized water and acidic deionized water, and also flexibility test were performed. The carbon layer based on SBS carbon paste (SBS-CP) was intact after adhesion tests and over 1017 cycles of flexibility test. The one based on PMMA carbon paste (PMMA-CP) didn't tolerate all mechanical tests and disintegrated. The carbon layer based on EC carbon paste (EC-CP) partly damaged after adhesion tests and didn't pass the flexibility test. The best efficiency of 18.6 % was obtained for a device based on SBS-CP and significant shelf-life stability over 172 days stored in relative humidity of 40 % and dark.

Inorganic hole transport layer for lead free bismuth halide perovskite for photovoltaic device

The finest Hole Transport Layer (HTL) with extraordinary optical and electrical properties are significantly influenced the Power Conversion Efficiency (PCE) of the photovoltaic device. Inorganic hole transport materials exhibit better performance than organic hole transport materials. Herein, we demonstrated that optoelectronic properties of inorganic materials of NiO doped with Cu as Hole Transport Layer (HTL) for Lead free Bismuth halide perovskite solar cell. Solution process method of sol – gel was used to synthesize p-type NiO doped with Cu and yield nano particles of high quality. Cu + doped into Ni2+ sites has improved the crystallization of nanoparticles, carrier mobility and carrier electric properties. Results of the study revealed that the Enhancement of electrical conductivity of about 2 % is obtained for NiO doped with Cu which is ∼1.287 × 10−02 compared to the pristine NiO which is ∼2.655 × 10−03.

A facile method to obtain colloidal dispersions of nickel hydroxide: Improving the processing of nickel oxide and facilitating its upscaling for perovskite-type solar devices

Nickel hydroxide has been successfully employed as a precursor to the widely used, inorganic hole transport material (HTM) nickel oxide (NiOx). However, manufacturing NiOx HTM layers from nickel hydroxide is more complicated than those involving organometallic precursors due to its poor solubility/dispersibility. We report here a substantial increase in nickel hydroxide dispersibility in organic solvents by complexing it with monoethanolamine. These improvements have enabled us to develop a simpler method for processing nickel hydroxide that resemble the known sol-gel method. The new metal complex remains dispersed for months and converts to nickel oxide at a temperature similar to that of nickel hydroxide (270–300 ºC). An extensive characterisation of NiOx films obtained from the deposited precursor has been carried out. Perovskites solar cells have also been built with these films as a proof of concept, showing promising results for the layers sintered at low (270 ºC) and high (500 ºC) temperatures. The pixel with highest efficiency for both sintering temperatures were 14.7 % and 16.7 %, respectively, which are close to or surpass the ones of the control samples (15.4 % and 15.7 %, respectively). The applied unpaired t-test statistical method showed that the mean efficiency values for our thick samples prepared at 270 °C are not statistically different from those of the control cells. Furthermore, the samples prepared at 500 °C presented a significant statistical difference with the control cells, showing higher average efficiencies (12.8 % and 13.3 % versus 11.4 % and 11.7 %, reverse and forward measurements, respectively). The simplicity of the manufacturing method developed, together with the use of non-toxic organic compounds for its preparation and the promising results observed in solar devices, makes it suitable for being upscaled.

Interface Defects Dependent on Perovskite Annealing Temperature for NiOX-Based Inverted CsPbI2Br Perovskite Solar Cells.

Nickel oxide (NiOX) is an ideal inorganic hole transport material for the fabrication of inverted perovskite solar cells owing to its excellent optical and semiconductor properties. Currently, the main research on developing the performance of NiOX-based perovskite solar cells focuses on improving the conductivity of NiOX thin films and preventing the redox reactions between metal cations (Ni3+ on the surface of NiOX) and organic cations (FA+ or MA+ in the perovskite precursors) at the NiOX/perovskite interface. In this study, a new type of interface defects in NiOX-based CsPbI2Br solar cells is reported. That is the Pb2+ from CsPbI2Br perovskites can diffuse into the lattice of NiOX surface as the annealing temperature of perovskites changes. The diffusion of Pb2+ increases the ratio of Ni3+/Ni2+ on the surface of NiOX, leading to an increase in the density of trap state at the interface between NiOX and perovskites, which eventually results in a serious decline in the photovoltaic performance of solar cells.

Improvement of Thermal Stability and Photoelectric Performance of Cs2PbI2Cl2/CsPbI2.5Br0.5 Perovskite Solar Cells by Triple-Layer Inorganic Hole Transport Materials.

Conventional hole transport layer (HTL) Spiro-OMeTAD requires the addition of hygroscopic dopants due to its low conductivity and hole mobility, resulting in a high preparation cost and poor device stability. Cuprous thiocyanate (CuSCN) is a cost-effective alternative with a suitable energy structure and high hole mobility. However, CuSCN-based perovskite solar cells (PSCs) are affected by environmental factors, and the solvents of an HTL can potentially corrode the perovskite layer. In this study, a Co3O4/CuSCN/Co3O4 sandwich structure was proposed as an HTL for inorganic Cs2PbI2Cl2/CsPbI2.5Br0.5 PSCs to address these issues. The Co3O4 layers can serve as buffer and encapsulation layers, protecting the perovskite layer from solvent-induced corrosion and enhancing hole mobility at the interface. Based on this sandwich structure, the photovoltaic performances of the Cs2PbI2Cl2/CsPbI2.5Br0.5 PSCs are significantly improved, with the power conversion efficiency (PCE) increasing from 9.87% (without Co3O4) to 11.06%. Furthermore, the thermal stability of the devices is also significantly enhanced, retaining 80% of its initial PCE after 40 h of continuous aging at 60 °C. These results indicate that the Co3O4/CuSCN/Co3O4 sandwich structure can effectively mitigate the corrosion of the perovskite layer by solvents of an HTL and significantly improves the photovoltaic performance and thermal stability of devices.

Spin-coated high mobility MoO3 thin film for designing highly efficient lead-free perovskite solar cells

Among the thin film-photovoltaics, perovskite solar cells (PSCs) are one of the most developing topics of research in recent times. Research records reveal that around 26 % efficiency in PSCs has already been achieved so far. However, the commercialization of those PSCs is hindered due to the toxicity of lead (Pb), and the instability of organic cations as well as structural volatility. Several inorganic materials including inorganic hole transport layer (HTL) have recently been proposed and developed to reduce the organic part in the device structure. We fabricate MoO3 thin film materials and conduct a detailed study to realize the potential of MoO3 as a unique HTL for application in PSCs. The synthesis of MoO3 thin film includes several characterization techniques e.g. XRD, FESEM, EDX, UV–Vis, and Hall Effect measurement. We design a MoO3 thin film-based, lead-free PSC structure of FTO/MoO3/PTAA/(FA)2BiCuI6/ZnO/Ag and perform numerical analysis using the SCAPS-1D simulation tool. In the device simulation process, we use the experimentally obtained optoelectrical properties of the MoO3 film and achieve a maximum efficiency of around 22.28 % in a contained lead-free PSC.

Physically‐Deposited Hole Transporters in Perovskite PV: NiOx Improved with Li/Mg Doping

AbstractNickel oxide (NiOx) has received a lot of attention as an inorganic hole transport material (HTM) in perovskite solar cells (PSCs) during the last decade, owing to its high hole mobility, chemical stability, good optical transparency, and suitable energy levels that align with the valance band of the perovskite absorber methylammonium lead iodide (MAPbI3). This study explores Li and Mg co‐doped NiOx thin films physically‐deposited from developed sputtering targets obtained through cold isostatic pressing and sintering. After sputtering, the structural, elemental, morphological, optical, and electrical properties of the layers are investigated by XRD, XPS, SEM, AFM, UV–vis spectrophotometer, and Hall‐effect; revealing that crystalline, homogeneous, and smooth films are obtained. In particular, improvements in mobility and conductivity values are observed with Li and Mg doping, which contribute to enhanced PSC performance when used as an HTM layer in the glass‐indium tin oxide (ITO)/NiOx‐based HTM/MAPbI3/phenyl butryic acid methyl ester (PCBM)/bathocuproine (BCP)/Ag architecture. The champion solar cell achieves PCE of 15.52%. In addition, the average values of all samples are boosted, JSC (from 13.21 to 15.60 mA cm−2) and FF (from 59.32% to 67.7%), relative to pristine HTM, resulting in a pronounced PCE increment of up to 30% with the HTM film sputtered by a single target of co‐doped material.

All-Inorganic Hydrothermally Processed Semitransparent Sb2S3 Solar Cells with CuSCN as the Hole Transport Layer.

An inorganic wide-bandgap hole transport layer (HTL), copper(I) thiocyanate (CuSCN), is employed in inorganic planar hydrothermally deposited Sb2S3 solar cells. With excellent hole transport properties and uniform compact morphology, the solution-processed CuSCN layer suppresses the leakage current and improves charge selectivity in an n-i-p-type solar cell structure. The device without the HTL (FTO/CdS/Sb2S3/Au) delivers a modest power conversion efficiency (PCE) of 1.54%, which increases to 2.46% with the introduction of CuSCN (FTO/CdS/Sb2S3/CuSCN/Au). This PCE is a significant improvement compared with the previous reports of planar Sb2S3 solar cells employing CuSCN. CuSCN is therefore a promising alternative to expensive and inherently unstable organic HTLs. In addition, CuSCN makes an excellent optically transparent (with average transmittance >90% in the visible region) and shunt-blocking HTL layer in pinhole-prone ultrathin (<100 nm) semitransparent absorber layers grown by green and facile hydrothermal deposition. A semitransparent device is fabricated using an ultrathin Au layer (∼10 nm) with a PCE of 2.13% and an average visible transmittance of 13.7%.

Halogen doping of p-type inorganic hole transport layer: electronic nature-based dopant engineering for modulating hole selectivity in inverted planar perovskite solar cells

The role of metal cation and halide anion dopants in regulating the properties of NiOx hole transport layer (HTL) was explored. This study confirms that halide dopants also increase the Ni3+ defect density and work function of p-type inorganic HTL.

Influence of cobalt doping on structural and optical properties of copper oxide expected as an inorganic hole transport layer for perovskite solar cell

Influence of cobalt doping on structural and optical properties of copper oxide expected as an inorganic hole transport layer for perovskite solar cell

Charge-carrier engineering of staggered-gap p-CuAlO2/β-Ga2O3 bipolar heterojunction for self-powered photodetector with exceptional linear dynamic range and stability

Beta-gallium oxide (β-Ga2O3)-based heterojunction photodetectors (HJPDs) based on p-n heterojunction have drawn a lot of attention since p-type doping of β-Ga2O3 is challenging to perform. Thus, choosing affordable and effective inorganic hole transport layers (HTLs) is a crucial first step in commercializing PDs. Copper aluminum oxide (p-CuAlO2) is a very likely candidate material for heterojunction with β-Ga2O3, because of its large hole mobility for use in solar-blind photodetectors and high-power electronics. In this study, we propose employing a p-CuAlO2 interlayer for built a β-Ga2O3-based SBUV HJPDs by regulating the oxygen flow rate (OFR) from 0 % to 30 % using the RF magnetron sputtering (RFMS) technique. Prior to building the p-CuAlO2/β-Ga2O3 HJPDs, the heterojunction band alignment was established and displayed staggered-gap band alignment with a valence band (ΔEV) offset of 1.1 eV and conduction band offset (ΔEC) of 0.65 eV with OFR of 30 %. In response to the UV-C (255 nm) wavelength, the good optoelectronic device properties such as low dark current of ∼10−12 A, large photo-to-dark current (Ilight/Idark) ratio (∼104), responsivity (R) (26.36 mA/W), detectivity (D*) (2.87 × 1010 cmHz1/2W−1), external quantum efficiency (EQE) (1.28 × 104 %), noise-equivalent power (NEP) (0.03 pWHz−1/2), linear dynamic range (LDR) (99.13 dB), and comparable rise (τr) and decay times (τd) of 0.25 s and 0.15 s respectively, were demonstrated for p-CuAlO2/β-Ga2O3 HJPDs with OFR of 30 % and also compared with pristine Pt/β-Ga2O3 Schottky barrier diode photodetector (SBDPD). The band offset at the p-CuAlO2/β-Ga2O3 interface is employed to explain the improvement of p-CuAlO2/β-Ga2O3 HJPDs. The incorporation of p-CuAlO2 into Pt/β-Ga2O3 SBDPD lead to an improved extraction efficiency of the generated free hole carriers under illumination. The Silvaco TCAD simulator was employed to get insight into the function of the p-CuAlO2 layer. The investigation focused on analyzing the variation profile of the recombination rate and electric field in Pt/β-Ga2O3 SBDPD and p-CuAlO2/β-Ga2O3 HJPD with OFR of 30 %. The outcomes demonstrate the stability and electron transfer impact of staggered gap p-CuAlO2/β-Ga2O3 HJPDs. Our findings show that the p-CuAlO2/β-Ga2O3 HJPDs have a great deal of potential as a candidate structure for the Ga2O3-based modern optoelectronic technologies.

Toward Efficient and Fully Scalable Sputtered NiOx‐Based Inverted Perovskite Solar Modules via Co‐Ordinated Modification Strategies

Sputtered nickel oxide (NiOx) has become one of the most promising inorganic hole transport layers for p–i–n perovskite solar cells (PSCs) due to its appealing features such as its robust nature, low material cost, and easy integration to tandem structures and large‐area applications. However, the main drawback with NiOx‐based PSCs is typically low open‐circuit voltage (VOC) due to the inferior energy‐level alignment, low charge mobility, and high recombination at the interface. Herein, two types of phosphonic acid self‐assembled monolayers (SAMs) deposited by blade coating as an interfacial layer to modulate the sputtered NiOx/perovskite interface properties are used. While sputtered NiOx serves as a conformally coated hole selective layer, the ultrathin SAM interlayer facilitates the hole extraction and minimizes the energy loss at the interface. Co‐ordinately introduced stabilizing additive, namely octadecyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (I‐76), further improves the device performance of NiOx/SAM‐based PSCs, resulting in VOC of 1.14 V and a power conversion efficiency of 21.8%. By applying these strategies for perovskite module upscaling, aperture area module efficiencies of 19.7%, 17.5%, and 15.5% for perovskite minimodules of 4, 16, and 100 cm2 are demonstrated, corresponding to active area module efficiencies of 20.4%, 18.0%, and 16.4%, respectively.

Enhancement in Efficiency of Methyl Ammonium Tin Iodide-Based Perovskite Solar Cell Using SCAPS-1D

Perovskite solar cells came to limelight owing to their simple fabrication processes, cost-effectiveness, better optoelectronic characteristics and outstanding power conversion efficiencies (PCEs). These solar cells have simply outpaced their rival cells since the alteration from aqueous hole transport layers (HTLs) to solid HTLs. Various layers of a perovskite cell viz. light absorber layer, electron transport layer (ETL) and HTL play a decisive role in ascertaining its performance. Today, various types of organic and inorganic HTLs are available but inorganic HTLs have gained an upper hand over their organic counterparts in terms of stability, cost, fabrication and material properties which represent them as a prospective candidate for optimum perovskite device. Copper antimony sulfide (CuSbS[Formula: see text] is a common HTL available in abundance with the benefit of an adequate bandwidth of 1.54[Formula: see text]eV. In addition, CuSbS2 possesses substantial band aligning and electron inhibiting features. This research paper elaborates a relative study of two perovskite solar devices possessing discrete inorganic hole transport layers, i.e., cuprous iodide (CuI) and copper antimony sulfide (CuSbS[Formula: see text], and discrete perovskite layers, i.e., MAPbI[Formula: see text]Cl[Formula: see text] and MASnI3, using the same negative charge transport layer, i.e., Cd[Formula: see text]Zn[Formula: see text]S, through numerical simulation employing SCAPS-1D. The effects of thickness, defect density and doping concentration with respect to absorbing layer on the efficiency and other parameters of perovskite layers are also discussed. By employing CuSbS2 with MASnI3 in the proposed device, the solar cell parameters are efficacious enough demonstrating the [Formula: see text] of 1.10[Formula: see text]V, PCE of 31.11%, fill factor (FF) of 83.05% and [Formula: see text] of 33.75[Formula: see text]mA[Formula: see text]⋅[Formula: see text]cm[Formula: see text].

An Experimental and Simulation Study of Cu6BiAgI10 Photovoltaics with Various Organic and Inorganic Hole Transport Layers for the Improved Photovoltaic Performance of Solar Cells

An Experimental and Simulation Study of Cu₆BiAgI₁₀ Photovoltaics with Various Organic and Inorganic Hole Transport Layers for the Improved Photovoltaic Performance of Solar Cells