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•Ionic liquids (ILs) aided-device engineering champions is widely reviewed.•The role of ILs in the production of high-quality perovskite film is discussed.•ILs can potentially improve ...the long-term stability of perovskite solar cells.•ILs represents a significant step toward reliable perovskite PV technology.
The efficiency of perovskite solar cells (PSCs) is rapidly increasing, so that their long-term operational stability has become a major focus for commercialization and market adoption. The development of novel strategies and materials to improve the stability of small and large solar modules without compromising power conversion efficiency (PCE) is an ongoing challenge. Ionic liquids (ILs) are emerging as useful additives, solvents, and charge transport materials for the preparation of highly efficient perovskite films. Perovskite crystallizes slowly in ILs to form large and uniform grains, and PSCs fabricated with high-quality perovskite films are efficient and stable. Herein we review recently developed systemic device engineering, and we discuss the impact of ILs in the production of highly efficient and stable PSCs. This review is intended to serve as a guide to develop highly crystalline perovskite films with larger grains and more homogeneous morphologies, all of which contribute to enhancing the stability of PSC performance. Recent progress in the use of ILs as solvents and additives for PSCs is a significant step toward developing reliable perovskite photovoltaic devices. Finally, we discuss challenges and future research directions for the fabrication of efficient and stable PSCs.
Highlights
Industrially viable bottom-up spray pyrolysis deposition technique was used to prepare the highly compact TiO
2
film, which is a vital element for the multi-layer front contact.
The ...optimization of the front contact is presented by fabricating reproducible and efficient perovskite solar cells
Multi-layer front contact is applied to realize efficient perovskite single-junction and perovskite/perovskite tandem solar cells, where optics and electrical effects of solar cells are studied by optically coupled 3D electromagnetic simulations.
The photovoltaic performance of perovskite solar cells (PSCs) can be improved by utilizing efficient front contact. However, it has always been a significant challenge for fabricating high-quality, scalable, controllable, and cost-effective front contact. This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells (TSCs). As a critical part of the front contact, we prepared a highly compact titanium oxide (TiO
2
) film by industrially viable Spray Pyrolysis Deposition (SPD), which acts as a potential electron transport layer (ETL) for the fabrication of PSCs. Optimization and reproducibility of the TiO
2
ETL were discreetly investigated while fabricating a set of planar PSCs. As the front contact has a significant influence on the optoelectronic properties of PSCs, hence, we investigated the optics and electrical effects of PSCs by three-dimensional (3D) finite-difference time-domain (FDTD) and finite element method (FEM) rigorous simulations. The investigation allows us to compare experimental results with the outcome from simulations. Furthermore, an optimized single-junction PSC is designed to enhance the energy conversion efficiency (ECE) by > 30% compared to the planar reference PSC. Finally, the study has been progressed to the realization of all-perovskite TSC that can reach the ECE, exceeding 30%. Detailed guidance for the completion of high-performance PSCs is provided.
In the design of electron-transport layers (ETLs) to enhance the efficiency of planar perovskite solar cells (PSCs), facile electron extraction and transport are important features. Here, we consider ...the effects of different titanium oxide (TiO2) polymorphs, anatase and brookite. We design and fabricate high-phase-purity, single-crystalline, highly conductive, and low-temperature (<180 °C)-processed brookite-based TiO2 heterophase junctions on fluorine-doped tin oxide (FTO) as the substrate. We test and compare single-phase anatase (A) and brookite (B) and heterophase anatase–brookite (AB) and brookite–anatase (BA) as ETLs in PSCs. The power-conversion efficiencies (PCEs) of PSCs with low-temperature-processed single-layer FTO-B as the ETL were as high as 14.92%, which is the highest reported efficiency of FTO-B-based single-layer PSC. This implies that FTO-B serves as an active phase and can be a potential candidate as an n-type ETL scaffold in planar PSCs. Moreover, the surface of highly crystalline brookite TiO2 exhibits a tendency toward interparticle necking, leading to the formation of compact scaffolds. Furthermore, PSCs with heterophase junction FTO-AB ETLs exhibited PCEs as high as 16.82%, which is superior to those of PSCs with single-phase anatase (FTO-A) and brookite (FTO-B) as the ETLs (13.86% and 14.92%, respectively). In addition, the PSCs with FTO-AB exhibited improved efficiency and decreased hysteresis compared with those with FTO-BA (13.45%) due to the suitable band alignment with the perovskite layer, which resulted in superior photogenerated charge-carrier extraction and reduced charge accumulation at the interface between the heterophase junction and perovskite. Thus, the present work presents an effective strategy by which to develop heterophase junction ETLs and manipulate the interfacial energy band to further improve the performance of planar PSCs and enable the clean and eco-friendly fabrication of low-cost mass production.
Abstract
In this study, a new, simple, and novel oblique electrostatic inkjet (OEI) technique is developed to deposit a titanium oxide (TiO
2
) compact layer (CL) on fluorine-doped tin oxide (FTO) ...substrate without the need for a vacuum environment for the first time. The TiO
2
is used as electron transport layers (ETL) in planar perovskite solar cells (PSCs). This bottom-up OEI technique enables the control of the surface morphology and thickness of the TiO
2
CL by simply manipulating the coating time. The OEI-fabricated TiO
2
is characterized tested and the results are compared with that of TiO
2
CLs produced by spin-coating and spray pyrolysis. The OEI-deposited TiO
2
CL exhibits satisfactory surface coverage and smooth morphology, conducive for the ETLs in PSCs. The power-conversion efficiencies of PSCs with OEI-deposited TiO
2
CL as the ETL were as high as 13.19%. Therefore, the present study provides an important advance in the effort to develop simple, low-cost, and easily scaled-up techniques. OEI may be a new candidate for depositing TiO
2
CL ETLs for highly efficient planar PSCs, thus potentially contributing to future mass production.
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•Low temperature processed high-quality TiO2 nanoparticles film were prepared.•TiO2 layer was optimized while fabricating efficient perovskite solar cells.•3D opto-electrical ...simulations investigate optical and electrical properties of the device.•Efficient nanophotonic front contact is designed for efficient perovskite solar cells.•Optimized device enhances ECE by 25 ~ 30%, up to 23%, compared to the flat contact device.
We report on the preparation and optimization of low temperature (<200 °C) processed TiO2 film as an electron transport layer (ETL) for high-performance perovskite solar cells (PSCs) compatible with flexible substrates. A high-quality ETL is spin-coated from hydrothermal synthesized single-phase crystalline anatase TiO2 nanoparticles (NPs) with an average diameter of 6 ~ 10 nm. The surface of the high crystallite TiO2 NPs reveals a tendency toward interparticle necking, facilitating compact scaffolds, resulting in PSCs with high power conversion efficiencies (PCEs). The influence of low and high temperature treated TiO2 ETL on the device performance is studied. The best planar device fabricated in superstrate configuration (sup-C) exhibits a PCE of 17.1% with a JSC of 20.3 mA/cm2. The PCE can be increased by ~ 25%, up to 23%, by moving from planar architecture in sup-C to the textured solar cell in substrate configuration (sub-C). The PSC covered with a nanophotonic-structured front contact allows gaining 8% and 15% on VOC and JSC, respectively, where 2/3 of JSC gain is attributed to improved light incoupling, while the remaining 1/3 is due to increased diffraction at long wavelengths. The optical and electrical characteristics of the devices are investigated by 3D finite-domain time-domain (FDTD) and finite element method (FEM) rigorous simulations. Detailed guidelines on the nanophotonic design are provided.
We report a simple method to achieve efficient nanostructured organic photovoltaics via patterning copper iodide (CuI) nanocrystals on indium tin oxide by glancing angle deposition. The strong ...interfacial interaction between zinc phthalocyanine (ZnPc) and CuI leads to the formation of nanopillar arrays with lying-down molecular order, which greatly improve light absorption and surface roughness for exciton dissociation. Optimized ZnPc/C60 bilayer cell has a power conversion efficiency of 4.0 ± 0.1%, which is about 3-fold larger than that of conventional planar cell.
Living systems achieve sophisticated functions using supramolecular protein assemblies, in which the protein building blocks possess a specific secondary structure and are noncovalently arranged in a ...preprogrammed manner. Herein, we demonstrate the one-step synthesis of one-dimensional macromolecular assemblies by simply mixing a glycine-based isocyanide with a nickel catalyst, in which helical constituent polymers are linked end-to-end through multiple hydrogen bonds. The applicable scope of this approach is not confined to a particular monomer bearing a specially designed pendant, but covers a wide range of glycine-based isocyanides with or without aromatic and other functional groups. Surprisingly, copolymerization with an analogous chiral isocyanide (1 mol %) afforded an almost perfect one-handed helical supramolecular fiber owing to intramolecular/intermolecular dual chiral amplifications. The simplicity and broad applicability of this approach, which can also afford exquisite chiral amplification, enable the creation of a wide variety of functional supramolecular assemblies and provide access to new supramolecular materials.
We present a strategy for photon management in front contact of perovskite solar cells (PSCs) compatible with tandem and flexible PSCs capable of optimizing device characteristics while providing an ...additional mechanism to overcome excessive focusing that affects the device’s photostability. Rigorous validation of the numerical modeling used was performed by fabricating PSCs in a superstrate configuration optimized to reach high performance, ECE = 17.4%, VOC = 1.02 V, JSC = 22.3 mA/cm2, and FF = 77%. These 3D electromagnetic simulations combining the finite-difference time-domain (FDTD) and finite element method (FEM) techniques provide detailed insights of the photonic and electrical effects in PSCs. Numerical optimization of the dual capabilities of a novel nanostructured front contact enables control of the absorbed power density distribution to maximize efficiency while simultaneously minimizing nanostructure-related sub-wavelength focusing effects. In-depth analysis of the proposed photon management reveals enhanced electrical characteristics to maximize charge extraction leading to JSC enhancements of ~15 that can be as high as 33% for ultra-thin active layers suitable for flexible PSCs compared to planar PSCs performance. Furthermore, we show that the design of the front contact layer’s nanostructure enables control of the power density distribution in the device to engineer PSCs' photostability without compromising performance enhancements afforded by the nanophotonic front contact. Details of the nanophotonic front contact, device, and fabrication process are provided.
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•The front contact integrated with hybrid nanoholes is designed for efficient perovskite solar cells (PSCs).•Demonstrates the ability to modulate the illumination for high efficiency and better photostability of PSCs.•Optoelectronic device modeling and performance, including photonic response, were investigated by 3D Multiphysics approach.•Validation of the Multiphysics approach against high-quality PSC’s detailed experimental data is conducted.•The proposed nanophotonic device allows enhancing JSC and ECE by 15~33% and 30%, respectively, compared to the reference device.
Interface engineering plays a promising strategy to produce highly efficient planar heterojunction (PHJ) perovskite solar cells. The deep trap states on the compact-TiOx surface leading to a large ...leakage current and recombination of charge carriers. To solve the problems, interfacial engineering of electron collecting layer (ECL) compact-TiOx by a thin-layer of one-step solution-processed and low-cost organic material is applied. In contrast, commonly used PCBM is still expensive material. Herein, a new, low-temperature processable higher potential of 60fulleropyrrolidine derivatives named as N-phenyl60fulleropyrrolidines (PNP) was introduced as an interfacial modification of ECL compact-TiOx with the varying thickness of 10, 20, and 30nm to replace the commonly used PCBM in PHJ perovskite solar cells. The modified surface morphology was achieved by introducing PNP interfacial layers that enhanced the surface-energy properties of the cells in terms of enhanced photocurrent. Compared with PCBM, PNP features a higher electronic mobility and stronger hydrophobic nature. The enhancement of power conversion efficiency was obtained from 5.12% to 8.23%, with an increase in short-circuit current density (Jsc) from 11.90 to 21.44mAcm−2 and fill factor (FF) from 0.49 to 0.56 owing to insertion of optimum 10-nm-thickness PNP that led to more efficient electron transport and charge extraction in the solar cell performances. The present work provides an important sign in the aspects to the low-cost mass production of perovskite solar cells.
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•A new design, low-temperature processable higher potential of N-phenyl60fulleropyrrolidines (PNP) was introduced as an interfacial modification of electron collecting layer amorphous compact-TiOx.•Investigate the effect upon the varying thickness of PNP interfacial layer on the resulting device performances.•The optimized morphology obtained by surface-energy modification enhanced the photocurrent of the corresponding solar cell.•Charge transfer was efficiently enhanced using insertion of PNP between the perovskite and amorphous compact-TiOx layer.
Recently, efficiency of organic solar cells (OSCs) with conjugated polymers and fullerene derivatives has been increased, in most cases by improving their short-circuit current density. Regarding the ...other photovoltaic parameters, the open-circuit voltage (
V
OC) remains controversial. In this study, we investigated the relation between the
V
OC and the energy difference (Δ
E) between the highest occupied molecular orbital of the donor material and the lowest unoccupied molecular orbital of the acceptor. The simple linear relation between
V
OC and Δ
E was not observed in the polymer-based OSCs. There must be some factor that decreased the
V
OC of the cells.
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