Inverted Planar Perovskite Solar Cells Research Articles

One-step electrodeposition of CuSCN/CuI nanocomposite and its hole transport-ability in inverted planar perovskite solar cells

The synthesis of CuSCN/CuI nanocomposite by single-step electrodeposition is developed. The surface morphology and film thickness are controlled by changing the electrochemical potential and deposition time. The mixed-phase formation of CuSCN/CuI is confirmed through x-ray diffraction and Raman spectral analysis. Nanopetal (NP) like morphology of CuSCN/CuI is observed in FESEM micrographs. Interestingly, the NPs density and thickness are increased with increasing the deposition potential and time. The device fabricated using CuSCN/CuI nanocomposite as a hole transport layer (HTL) which is grown for 2 min delivers the best photovoltaic performance. The maximum power conversion efficiency of 18.82% is observed for CuSCN/CuI NP with a density of 1153 μm−2 and thickness of 142 nm. The charge transfer ability of the CuSCN/CuI NP HTL is analyzed by electrochemical impedance spectroscopy. Based on the observation, moderate charge transport resistance and optimum film thickness are required for achieving maximum photovoltaic performance in perovskite solar cells (PVSCs). Thus, the developed CuSCN/CuI NP HTL is a potential candidate for PVSCs.

Improvement of fill factor by the utilization of Zn-doped PEDOT:PSS hole-transport layers for p-i-n planar type of perovskite solar cells

Poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate (PEDOT:PSS) is a widely-known conductive polymer mixture that is mostly engaged as a hole transport layer (HTL) in organic and perovskite solar cells (PSCs). In this study, it has been demonstrated that the use of Zn as an additive in PEDOT:PSS solution improved the photovoltaic performance of the ambient air solution-based fabrication of methylammonium lead tri-iodide (MAPbI3) based devices. The short circuit current density (JSC) of the device increased from 15.4 to 17.2 mA/cm2, while the fill factor (FF) improved from 0.70 to 0.83 by using Zn-doped PEDOT:PSS as a hole transport layer (HTL), which is a record value for only γ-butyrolactone (GBL) based MAPbI3 PSCs. Additionally, open-circuit (VOC) value is boosted up from 890 to 925 mV by Zn-doping, which might be linked to the increased work function of the investigated HTLs. Moreover, the synergetic effect of improved electrical conductivity and hole mobility of PEDOT:PSS film and decreased the trap density of perovskite led to an increase of 37% in power conversion efficiency (PCE) and the stability of the inverted planar PSCs.

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

Summary Understanding defects is of paramount importance for the development of stable halide perovskite solar cells (PSCs). However, isolating their distinctive effects on device efficiency and stability is currently a challenge. We report that adding the organic molecule 3-phosphonopropionic acid (H3pp) to the halide perovskite results in unchanged overall optoelectronic performance while having a tremendous effect on device stability. We obtained PSCs with ∼21% efficiency that retain ∼100% of the initial efficiency after 1,000 h at the maximum power point under simulated AM1.5G illumination. The strong interaction between the perovskite and the H3pp molecule through two types of hydrogen bonds (H…I and O…H) leads to shallow point defect passivation that has a significant effect on device stability but not on the non-radiative recombination and device efficiency. We expect that our work will have important implications for the current understanding and advancement of operational PSCs.

Passivation of Bulk and Interface Defects in Sputtered-NiOx-Based Planar Perovskite Solar Cells: A Facile Interfacial Engineering Strategy with Alkali Metal Halide Salts

Nickel oxide (NiOx) (deposited by sputtering (sp)) is a promising hole transport layer (HTL) for inverted planar perovskite solar cells. However, poor CH3NH3PbI3 crystallization, elimination of CH3...

Benzo[ghi]perylenetriimide derivatives as effective interfacial passivation and electron transporting layers for inverted perovskite solar cells

In this study, we synthesized three benzo[ghi]perylenetriimide (BPTI) derivatives—C4, C3A, and C3AI—having butyl, dimethylaminopropyl, and propylammonium iodide side chains, respectively, and applied them as electron-transport layers (ETLs) and interfacial layers for inverted planar perovskite solar cells (PSCs) and examined their ability to function as defect passivation agents. Our PSC structure was glass/indium tin oxide/NiOx/CH3NH3(MA) PbI3/BPTI/PCBM/BCP/Ag. We used X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, UV–Vis spectroscopy, X-ray diffraction spectroscopy, field-effect scanning electron microscopy, and atomic force microscopy to determine the optoelectronic properties of PSCs prepared with and without the BPTIs. We found that the BPTI derivatives interacted with the perovskite and altered its energy levels to enhance electron extraction in their respective devices. In particular, C3AI effectively passivated the surface defects of perovskite and decreased the interfacial resistance, thereby suppressing the hysteresis effect and improving the device performance. We obtained an optimized power conversion efficiency (PCE) of 20.3% for the C3AI-containing MAPbI3 device, with a remarkable fill factor of 80.0%—among the highest ever reported for an MAPbI3-based p-i-n PSC. Therefore, this paper provides a new strategy of using nonfullerene materials for dual functions (as ETLs and defect passivation) in 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.

Coordination Strategy Driving the Formation of Compact CuSCN Hole‐Transporting Layers for Efficient Perovskite Solar Cells

The preparation of a high‐quality CuSCN thin film is very important to guarantee its efficient performance in an electronic device. Herein, a coordination strategy is reported for the formation of a highly compact CuSCN hole‐transporting layer by retarding fast crystallization via constructing intermediate adducts, and investigated its application for perovskite solar cells (PSCs). Specifically, the strong coordination bond between CuSCN and pyridine derivate ligands results in the formation of a stable intermediate phase, which is further converted to compact CuSCN layers under thermal annealing. The configuration of the intermediate phase is demonstrated to be crucial for the subsequent assembly of high‐quality CuSCN layers and results in an improved performance of the devices. CuSCN thin films crystallized from an intermediate adduct, CuSCN‐(Cl‐Py), with a rippled sheet configuration show an exceptional surface uniformity and high hole mobility, which facilitates efficient hole extraction and suppresses charge recombination in PSCs, resulting in an enhanced device efficiency of 19.19%. That is the highest value of the inverted planar PSCs using CuSCN as a hole‐transporting layer to the best of the authors’ knowledge. This novel coordination strategy can be expected to be used in the preparation of other inorganic charge transporting materials for electronic devices.

Molecular weight effect of poly-TPD hole-transporting layer on the performance of inverted perovskite solar cells

Inverted planar perovskite solar cells (PSCs) with poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine) (PTPD) layer as hole-transporting layer (HTL) exhibit high power conversion efficiencies (PCEs) over 20%. However, the influence of PTPD’s molecular weight (Mw) on the performance of PSCs has not been reported yet. Herein, we employ PTPD with various molecular weights as HTL to fabricate highly efficient inverted planar PSCs. Our results show that PTPD with 75 kDa possesses superior conductivity, which can quicken the charge carrier extraction from perovskite to HTL. In addition, the MAPbI3 perovskite film atop the 75-kDa PTPD is smoother with higher crystallinity and lower defect density. As a result, inverted planar PSCs with 75-kDa PTPD as HTL deliver a highest PCE of 19.24%. Our work provides a beneficial reference for future preparation of stable and highly efficient inverted PSCs with polymer HTL.

Chemical passivation of the under coordinated Pb2+ defects in inverted planar perovskite solar cells via β-diketone Lewis base additives.

Hybrid organic-inorganic perovskite solar cells (PSCs) are promising new generations of solar cells, which is low in cost with high power conversion efficiency (PCE). However, PSCs suffer from structural defects generated from the under coordinated ions at the surface, which limits their photovoltaic performances. Herein we report, two β-diketone Lewis base additives 2,4-pentanedione and 3-methyl-2,4-nonanedione within the chlorobenzene anti-solvent to passivate the surface defects generated from the under coordinated Pb2+ ions in CH3NH3PbI3 perovskite films. The incorporation of the two β-diketone passivators could successfully enhance the open-circuit voltage of the PSCs by 52mV and 17mV for 3-methyl-2,4-nonanedione and 2,4-pentanedione, respectively, with improved PCE by 45% for 3-methyl-2,4-nonanedione compared to the pristine PSC. This enhancement in the photovoltaic performance of the PSCs can be attributed to passivation of the defects through the interaction between two carbonyl groups of the β-diketone Lewis base additives and the under coordinated Pb2+ defects in the perovskite film, which improved the PSCs PCE and stability.

Suppressing interfacial defect formation derived from in-situ-generated polyethylenimine-based 2D perovskites to boost the efficiency and stability NiOx-based inverted planar perovskite solar cells

Recently, NiOx-based inverted planar perovskite solar cells (PSCs) have achieved great progress. However, the lattice mismatch between NiOx hole-transport layers (HTLs) and perovskite active layers will result in interfacial defect formation, which severely influences device efficiency and stability. In this work, this is alleviated by coating of polyethylenimine cations (PEI•HI) on the surface of NiOx HTLs. The introduction of PEI•HI can not only effectively passivate the surface defects of NiOx films, but also induce the in-situ-generation of polyethylenimine (PEI)-based two-dimensional (2D) perovskite interlayers between NiOx and CH3NH3PbI3 (MAPbI3). Such PEI-based 2D perovskite interlayer can dramatically mitigate the lattice mismatch between NiOx and perovskites to suppress the interfacial defects formations and promote the high-quality crystal nucleation and growth of above perovskite films. Meanwhile, it is demonstrated that the molecular weights of PEI act the pivotal part in controlling the nucleation quality of perovskites. When employing PEI with molecular weight of 10,000 (PEI-1000), the high-crystalline perovskite film with large-sized grains and reduced interfacial defects is obtained and the champion PSC delivers a power conversion efficiency (PCE) of 19.23% with weak hysteresis effect and improved reproducibility and stability. Our work provides a promising approach to improve the lattice match between NiOx and perovskites for high-performance NiOx-based inverted planar PSCs.

Influence of Inorganic NiOx Hole Transport Layer on the Growth of CsBi3I10 Perovskite Films for Photovoltaic Applications

AbstractLead (Pb)‐free bismuth (Bi) halide perovskites are promising alternatives to Pb‐based ones for the fabrication of perovskite solar cells (PSCs). However, the energy‐level mismatch at the interface between Bi perovskite (CsBi3I10;CBI) and the charge carrier transport layer limits the performance of the PSCs. Here, spray pyrolysis processed nickel oxide (sp‐NiOx) is reported as a hole transport layer (HTL) for CBI‐based inverted planar PSCs. Influence of inorganic NiOx HTL is systematically studied on the structural and morphological properties of the CBI perovskite layer growth. The CBI perovskite deposited on top of the sp‐NiOx exhibits improved crystallinity. The fabricated sp‐NiOx layer also exhibits favorable optical and electrical properties. The deep valence band (−5.4 eV) of the sp‐NiOx HTL is able to reduce the energy‐level mismatch up to 0.3 eV at the interface with the CBI layer. The PSCs fabricated with sp‐NiOx as HTL also exhibits a power conversion efficiency (PCE) of 0.72%, with a short‐circuit current density of 2.89 mA cm−2. The sp‐NiOx HTL based device maintains 85% of its initial PCE value even after 100 h of light soaking. This work highlights the importance of having a suitable HTL along with appropriate interface engineering for the Bi halide photovoltaic devices.

Potassium Thiocyanate‐Assisted Enhancement of Slot‐Die‐Coated Perovskite Films for High‐Performance Solar Cells

Slot‐die coating is highly promising for scaled deposition of metal halide perovskite thin films. However, the power conversion efficiencies (PCEs) of slot‐die‐prepared perovskite solar cells (PSCs) still lag behind their spin‐casted counterparts. To resolve this issue, the crystal size and quality of slot‐die‐coated methylammonium lead triiodide (MAPbI3) perovskite films are dramatically improved via additive engineering using potassium thiocyanate (KSCN). The modified micrometer‐thick films have an average grain size of ≈11 μm and charge‐carrier parameters that are comparable with single‐crystal perovskites, such as a 1.89 μs lifetime, 136.65 ± 31.52 cm2 V−1 s−1 mobility, and 25.15 ± 3.55 μm diffusion length. Exploiting these enhanced properties, planar inverted PSCs with negligible hysteresis are fabricated and an average and a maximum PCE of 20.14% and 21.38%, respectively, are achieved which are among the highest reported values for slot‐die‐coated PSCs. Notably, our devices have a narrow PCE distribution along the slot‐die coating axis, highlighting slot‐die coating's promise to fabricate large‐scale, high‐performance PSCs.

A p-p+ Homojunction-Enhanced Hole Transfer in Inverted Planar Perovskite Solar Cells.

Perovskite solar cells (PSCs) have triggered a research trend in solar energy devices in view of their high power conversion efficiency and ease of fabrication. However, more delicate strategies are still required to suppress carrier recombination at charge transfer interfaces, which is the necessary path to high-efficiency solar cells. Here, a p-p+ homojunction was constructed on basis of NiO film to enhance hole transfer in an inverted planar perovskite solar cell. The homojunction was generated by fabricating a NiO/Cu:NiO bilayer film. The density functional theory calculation demonstrated the charge density difference in the two layers, which could generate a space charge region and a band bending at the junction, and the result was further proved by energy level structure analysis of NiO and Cu:NiO films. The designed homojunction could accelerate the hole transfer and inhibit carrier recombination at the interface between hole transfer layer and perovskite layer. Finally, the inverted planar perovskite solar cell with p-p+ homojunction showed an efficiency of 18.30 % and a high fill factor of 0.81, which were much higher than the counterpart of the PSCs individually using NiO or Cu:NiO as hole transfer layer. This work developed a new structure of hole transport layer to enhance the performance of PSCs, and also provided new ideas for design of charge transfer films.

Multiple functional groups synergistically improve the performance of inverted planar perovskite solar cells

Abstract Numerous defects may occur during the preparation of perovskite films, and these defects obstruct the charge transfer and accelerate the decomposition of films. Herein, the 1-propionate-4-amino-1,2,4-triazolium tetrafluoroborate (PATMBF4) is employed as a multifunctional additive for caesium (Cs), methylammonium (MA) and formamidinium (FA) triple-cation-based perovskites (CsFAMA) to prepare inverted planar solar cells. The amino group (-NH2) in PATM+ can donate free electron pair to form a Pb-N coordination bond with perovskite, which can not only regulate crystal growth, but also decrease the generation of charge recombination centers to make charge transfer more effective. The hydrogen bond formed between the carbonyl group (C O) contained in PATM+ and FA+ (O···H-N) restrains the migration of FA+ to the film surface, thus retarding the decomposition of film. Hence, the photoelectric conversion efficiency (PCE) of the champion device is as high as 21.35%. In addition, the PCE can sustain over 85% after exposure to air for 4000 h with a relative humidity of 40 ± 5%, and only drops by 10% in the case of 85 °C more than 1000 h (N2). It can retain 90% of PCE under the full-spectrum sunlight for 800 h (N2).

Solution-processable nickel–chromium ternary oxide as an efficient hole transport layer for inverted planar perovskite solar cells

Solution-processed ternary metal oxide NiCrO3 films were developed as competitive hole transport layers in inverted perovskite solar cells with an efficiency of 19.93%.

Research progress of inverted planar perovskite solar cells based on nickel oxide as hole transport layer

In recent years, organic-inorganic hybrid perovskite solar cells (PSCs) have attracted wide attention due to their high photoelectric conversion efficiency and simple preparation process. Hole transport layer (HTL) is one of the most critical components in PSCs. As a kind of inorganic HTL material, nickel oxide (NiO<sub><i>x</i></sub>) has been widely used in perovskite solar cells because of its excellent advantages, such as outstanding chemical stability, high carrier mobility, simple methods for its preparation, etc. In this paper, the applications of NiO<sub><i>x</i></sub> HTL in planar PSCs are systematically summarized from the aspects of the improvment of its structure and photoelectric properties by doping and interface modification. The reasons for affecting the device performances, <i>i.e</i>. fill factor, open-circuit voltage, short-circuit current, photoelectric conversion efficiency, and stability are emphatically analyzed from several aspects, such as energy level matching, hole mobility and crystallinity. In addition, the future development directions of the planar PSCs are prospected.

Synergistic Interface Layer Optimization and Surface Passivation with Fluorocarbon Molecules toward Efficient and Stable Inverted Planar Perovskite Solar Cells.

Large-size organic halide passivation has been considered an efficient approach to enhance the perovskite solar cell (PSC) efficiency and stability. Herein, a facile posttreatment strategy was demonstrated, wherein trifluoromethyl-phenethylamine hydrobromide (CF3-PEABr) is firstly used to passivate the perovskite film surface. The CF3-PEABr surface posttreatment could coordinate with halide dangling bonds that exist at the perovskite crystal surface. Moreover, the surface treatment with CF3-PEABr could efficiently passivate the defects in the perovskite film and suppress the nonradiative carrier recombination. As a result, a high efficiency of 21.3% is obtained, and an increment of 80 mV in Voc (a large Voc of 1.15 V, with a 0.42 V voltage deficit) occurs, compared to the control device. To relieve the hydrophobic nature properties of the -CF3 functional group and the dewetting problem of PCBM layer deposition, a surfactant Triton X-100 is used to modify the PCBM layer. Furthermore, the devices with CF3-PEABr posttreatment exhibit better operational, thermal (85°C), and long storage stabilities without any encapsulation.

Boosting the performance of planar inverted perovskite solar cells employing graphene oxide as HTL

The numerical simulation tool SCAPS-1D was used to analyze perovskite solar cell having the architecture ITO/ PEDOT:PSS or GO /CH3NH3PbI3-xClx/ PCBM /Au contains inverted planar hetero-junction device. In this work, we investigated the effect of inserting the Graphene Oxide (GO) as Hole Transport layer (HTL) on the performance of perovskite solar cells. Simulation results show that the use of GO as a hole transport layer is efficient. The efficiency of PSCs based on GO HTL was increased by about 1.6 % compared to the conventional PEDOT:PSS HTL device. The obtained results of optimizing the thickness of GO HTL exhibited an optimum value around 10 nm with an efficiency of 12.35 %, Voc of 1.19 V and FF of 54.8 %. We have also shown that the performance of device for high GO carrier density is a better than with low ones. In addition, increasing the temperature beyond the optimum value obtained around 320 K for both HTL materials (GO and PEDOT:PSS) has detrimental effect on the performance of the perovskite solar cells however the device is more sensitive to the temperature with PEDOT:PSS than the GO ones. The effect of band gap of GO on the performance of device is also studied. The obtained results underline the determining role playedby this parameter with an optimum value around 3.25 eV.

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

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 NiOx (Cu:NiOx) films and the photovoltaic performance of PSCs with Cu:NiOx HTLs were systematically studied. The Cu-doped NiOx with different doping concentrations was achieved by a high-temperature solid-state reaction, and Cu:NiOx 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 NiOx films, the Cu:NiOx films exhibit a higher electrical conductivity with a faster charge transportation and extraction for PSCs. By employing the prepared Cu:NiOx 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 NiOx 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 NiOx film is a promising HTL for realizing high-performance and air-stable PSCs.

Optoelectronic Modulation of Undoped NiOx Films for Inverted Perovskite Solar Cells via Intrinsic Defect Regulation

Ni vacancy (VNi) as an intrinsic defect plays an important role in the optical and electronic properties of NiOx films for inverted planar perovskite solar cell (PSC) applications. This work presen...