Lead Halide Perovskite Solar Cells Research Articles

TiO2 Nanocolumn Arrays for More Efficient and Stable Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (>25%) and low-cost fabrication. Yet, improvements are still needed for more stable and higher-performing solar cells. In this work, a series of TiO2 nanocolumn photonic structures have been intentionally fabricated on half of the compact TiO2-coated fluorine-doped tin oxide substrate by glancing angle deposition with magnetron sputtering, a method particularly suitable for industrial applications due to its high reliability and reduced cost when coating large areas. These vertically aligned nanocolumn arrays were then applied as the electron transport layer into triple-cation lead halide perovskite solar cells based on Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3. By comparison to solar cells built onto the same substrate without nanocolumns, the use of TiO2 nanocolumns can significantly enhance the power conversion efficiency of the perovskite solar cells by 7% and prolong their shelf life. Here, detailed characterizations on the morphology and the spectroscopic aspects of the nanocolumns, their near-field and far-field optical properties, solar cells characteristics, as well as the charge transport properties provide mechanistic insights on how one-dimensional TiO2 nanocolumns affect the performance of perovskite halide solar cells in terms of charge transport, light harvesting, and stability, knowledge necessary for the future design of higher-performing and more stable perovskite solar cells.

Stability of Lead and Tin Halide Perovskites: The Link between Defects and Degradation.

The field of photovoltaic research has been lately dominated by the rapid evolution of low-cost and high-efficiency hybrid organic lead halide perovskite solar cells. Despite the considerable progress made in the efficiency of such devices, the achievement of long-term material and device stability remains a challenge. In this Perspective, insights into the role structural defects play in the stability of these perovskite absorbers are examined, highlighting the critical importance of vacancy type defects as the initiation sites for moisture-, oxygen-, and light-induced degradation and the approaches that are emerging to help overcome these issues. In the second part of the Perspective we consider the stability of tin-based perovskites. Here, the Sn4+ defects that arise upon material degradation are described along with the strategies being developed to enhance stability and decrease their formation. Finally, the discussion is extended to innately more stable layered tin-based perovskites, identifying them as a route to the development of efficient lead-free perovskite solar cells.

TEMPOL-promoted oxygen doping of a polytriarylamine hole-transport layer for efficient and stable lead halide perovskite solar cells

In this study, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) is presented as an additive to modify a polytriarylamine-based hole transport layer (HTL) for perovskite solar cells assembled in a regular n–i–p configuration.

The low-power law emergent response of random RCC’ networks

In this paper, we analyse the emergent response of random resistor-capacitor (RC) networks, which are widely used in modeling binary composite materials. By simply introducing two kinds of capacitors C and C ′ , we simulate the size effect of micro-capacitors formed by dielectric regions separating conductive regions in real materials. A low-power law emergent response (low PLER) is obtained in the framework of these random networks which we will be naming (RCC’) therein. This simple model also explains the observed low frequency dispersion in porous sample of the perovskite lead zirconate titanate (PZT) as well as lead halide perovskite solar cells. The calculations has been achieved by using the well known Frank and Lobb algorithm. In addition, we investigate the effect of capacitor proportions and value ratios (C ′ /C ) on the PLER. A good agreement with EMA predictions is obtained at intermediate frequencies.

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.

Integration of a Hydrogenase in a Lead Halide Perovskite Photoelectrode for Tandem Solar Water Splitting.

Lead halide perovskite solar cells are notoriously moisture-sensitive, but recent encapsulation strategies have demonstrated their potential application as photoelectrodes in aqueous solution. However, perovskite photoelectrodes rely on precious metal co-catalysts, and their combination with biological materials remains elusive in integrated devices. Here, we interface [NiFeSe] hydrogenase from Desulfovibrio vulgaris Hildenborough, a highly active enzyme for H2 generation, with a triple cation mixed halide perovskite. The perovskite–hydrogenase photoelectrode produces a photocurrent of −5 mA cm–2 at 0 V vs RHE during AM1.5G irradiation, is stable for 12 h and the hydrogenase exhibits a turnover number of 1.9 × 106. The positive onset potential of +0.8 V vs RHE allows its combination with a BiVO4 water oxidation photoanode to give a self-sustaining, bias-free photoelectrochemical tandem system for overall water splitting (solar-to-hydrogen efficiency of 1.1%). This work demonstrates the compatibility of immersed perovskite elements with biological catalysts to produce hybrid photoelectrodes with benchmark performance, which establishes their utility in semiartificial photosynthesis.

Stability Issue of Perovskite Solar Cells under Real‐World Operating Conditions

Organic–inorganic lead halide perovskites solar cells (PSCs) show great potential in the photovoltaic system, reaching overall power conversion efficiencies (PCE) up to 25.2%. The rapid increase of PCE in PSCs has made them the rising star of the photovoltaics world, with great interest to the academic community. Long‐term stability under working environments remains a significant challenge for the commercialization of PSCs, particularly those using inorganic–organic halide lead perovskite absorbers. In this regard, only the devices that can maintain long‐term stability under conditions of temperature, humidity, and UV irradiation can be called stable solar cells. This Review highlights the sources for the chemical instability problems in conventional CH3NH3PbI3‐based perovskite solar cells from humidity instability, phase instability, thermal instability, and ion migration. In pursuit of highly stable PSCs, this article also discusses the strategies to stabilize PSCs through both external and internal aspects without sacrificing the PCE, specifically including additive engineering with surface passivation and composition engineering.

Improving Photovoltaic Performance Using Perovskite/Surface‐Modified Graphitic Carbon Nitride Heterojunction

Passivation strategies are considered as one of the most efficient methods to suppress nonradiative recombination of organic–inorganic lead halide perovskite solar cells (PSCs), leading to tremendous photovoltaic performance. An innovative 2D polymer, graphitic carbon nitride (g‐C3N4), as well as various organic groups (amino, sulfonic, nitrato, and hydroxy group), are widely used as passivation agents, according to the previous reports. Anchoring g‐C3N4 and the aforementioned organic groups as additives in perovskite can both heal charged defects around the grain boundaries by passivating the charge recombination center. In addition, the crystalline quality can also be enhanced by the incorporation of g‐C3N4, leading to improved conductivity of perovskite light absorber films that is beneficial for benign charge extraction efficiency. Inspired by the underlining mechanisms, a series of novel passivation molecules, functionalized g‐C3N4 (F‐C3N4) with assorted organic groups, is designed herein, yielding a champion power conversion efficiency (PCE) of 20.08% for NO3‐C3N4‐based p‐i‐n structure PSC, in comparison with that of PSC without passivation (17.85%). These findings present an efficient strategy to understand and design multiple facets of applications of novel passivation molecules to further improve the PCE of PSCs.

Additives in metal halide perovskite films and their applications in solar cells

Abstract The booming growth of organic-inorganic hybrid lead halide perovskite solar cells have made this promising photovoltaic technology to leap towards commercialization. One of the most important issues for the evolution from research to practical application of this technology is to achieve high-throughput manufacturing of large-scale perovskite solar modules. In particular, realization of scalable fabrication of large-area perovskite films is one of the essential steps. During the past ten years, a great number of approaches have been developed to deposit high quality perovskite films, to which additives are introduced during the fabrication process of perovskite layers in terms of the perovskite grain growth control, defect reduction, stability enhancement, etc. Herein, we first review the recent progress on additives during the fabrication of large area perovskite films for large scale perovskite solar cells and modules. We then focus on a comprehensive and in-depth understanding of the roles of additives for perovskite grain growth control, defects reduction, and stability enhancement. Further advancement of the scalable fabrication of high-quality perovskite films and solar cells using additives to further develop large area, stable perovskite solar cells are discussed.

Vacuum Fabrication: Efficient Cesium Lead Halide Perovskite Solar Cells through Alternative Thousand‐Layer Rapid Deposition (Adv. Funct. Mater. 44/2019)

Vacuum Fabrication: Efficient Cesium Lead Halide Perovskite Solar Cells through Alternative Thousand‐Layer Rapid Deposition (Adv. Funct. Mater. 44/2019)

Honeycomb-shaped charge collecting electrodes for dipole-assisted back-contact perovskite solar cells

Dipole-field-assisted charge-transporting-material-free lead halide perovskite solar cells (PSCs) using a back-contact configuration feature intrinsic advantages, such as no parasitic light absorption and high architectural defect tolerance. Herein, a newly designed, highly defect tolerant honeycomb-shaped back-contact (HBC) electrode was incorporated into dipole-field-assisted-back-contact PSCs, aiming to optimize the charge transport distance before being collected by the electrodes. HBC-PSCs with three feature sizes were fabricated in order to understand the effect of charge transport distance on device performance. The photovoltaic performance of HBC-PSCs correlates inversely proportional to the feature sizes. The mechanism behind the performance difference is elucidated via a detailed analysis through device current voltage characterization, transient photovoltage decay measurement and photocurrent mapping. A comprehensive comparison between honeycomb-shaped and interdigitated finger back-contact electrodes for PSCs is also conducted.

Nanostructured Perovskite Solar Cells.

Over the past decade, lead halide perovskites have emerged as one of the leading photovoltaic materials due to their long carrier lifetimes, high absorption coefficients, high tolerance to defects, and facile processing methods. With a bandgap of ~1.6 eV, lead halide perovskite solar cells have achieved power conversion efficiencies in excess of 25%. Despite this, poor material stability along with lead contamination remains a significant barrier to commercialization. Recently, low-dimensional perovskites, where at least one of the structural dimensions is measured on the nanoscale, have demonstrated significantly higher stabilities, and although their power conversion efficiencies are slightly lower, these materials also open up the possibility of quantum-confinement effects such as carrier multiplication. Furthermore, both bulk perovskites and low-dimensional perovskites have been demonstrated to form hybrids with silicon nanocrystals, where numerous device architectures can be exploited to improve efficiency. In this review, we provide an overview of perovskite solar cells, and report the current progress in nanoscale perovskites, such as low-dimensional perovskites, perovskite quantum dots, and perovskite-nanocrystal hybrid solar cells.

Design of low bandgap tin–lead halide perovskite solar cells to achieve thermal, atmospheric and operational stability

Low bandgap tin–lead iodide perovskites are key components of all-perovskite tandem solar cells, but can be unstable because tin is prone to oxidation. Here, to avoid a reaction with the most popular hole contact, we eliminated polyethylenedioxythiophene:polystyrenesulfonate as a hole transport layer and instead used an upward band offset at an indium tin oxide–perovskite heterojunction to extract holes. To suppress oxidative degradation, we improved the morphology to create a compact and large-grained film. The tin content was kept at or below 50% and the device capped with a sputtered indium zinc oxide electrode. These advances resulted in a substantially improved thermal and environmental stability in a low bandgap perovskite solar cell without compromising the efficiency. The solar cells retained 95% of their initial efficiency after 1,000 h at 85 °C in air in the dark with no encapsulation and in a damp heat test (85 °C with 85% relative humidity) with encapsulation. The full initial efficiency was maintained under operation near the maximum power point and near 1 sun illumination for over 1,000 h. Low bandgap tin–lead perovskites are crucial to making efficient all-perovskite tandem solar cells but have so far shown poor stability. By removing the hole transport layer and improving film morphology, Prasanna et al. demonstrate a low-gap perovskite solar cell that is stable for 1,000 h under heat, light and atmospheric conditions.

Sputtered Transparent Electrodes (IO:H and IZO) with Low Parasitic Near-Infrared Absorption for Perovskite–Cu(In,Ga)Se2 Tandem Solar Cells

Hybrid lead halide perovskite solar cells (PSCs) in tandem application with copper indium gallium diselenide (CIGS) solar cells represent one of the most promising all-thin-film technologies for ne...

Extremely Robust Gas-Quenching Deposition of Halide Perovskites on Top of Hydrophobic Hole Transport Materials for Inverted (p-i-n) Solar Cells by Targeting the Precursor Wetting Issue.

Lead halide perovskite solar cells afford high power conversion efficiencies, even though the photoactive layer is formed in a solution process. At the same time, solution processing may impose some severe dewetting issues, especially if organic, hydrophobic charge transport layers are considered. Ultimately, very narrow processing windows with a relatively large spread in device performance and a considerable lab-to-lab variation result. Here, we unambiguously identify dimethylsulfoxide (DMSO), which is commonly used as a co-solvent and complexing agent, to be the main reason for dewetting of the precursor solution on hydrophobic hole transport layers, such as polytriarylamine, in a gas-quenching-assisted deposition process. In striking contrast, we will show that N-methyl-2-pyrrolidon (NMP), which has a lower hydrophilic-lipophilic-balance, can be favorably used instead of DMSO to strongly mitigate these dewetting issues. The resulting high-quality perovskite layers are extremely tolerant with respect to the mixing ratio (NMP/dimethylformamide) and other process parameters. Thus, our findings afford an outstandingly robust, easy to use, and fail-safe deposition technique, yielding single (MAPbI3) and double (FA0.94Cs0.06PbI3) cation perovskite solar cells with high efficiencies (∼18.5%). Most notably, the statistical variation of the devices is significantly reduced, even if the deposition process is performed by different persons. We foresee that our results will further the reliable preparation of perovskite thin films and mitigate process-to-process variations that still hinder the prospects of upscaling perovskite solar technology.

Managing Energy Loss in Inorganic Lead Halide Perovskites Solar Cells

AbstractThough the cesium‐based inorganic perovskite solar cells (IPSCs) have developed rapidly in recent two years, the power conversion efficiency (PCE) is still far away from the Shockley–Queisser limit due to the large open‐circuit voltage (Voc) deficit, which results from the large energy loss (Eloss). Large Eloss has been a major obstacle for further efficiency improvement of IPSCs. In this review, the authors, for the first time, focus on investigating the Eloss of IPSCs and start from discussing the essence and origin of the Eloss. Then, the reported efficient methods for reducing the band tails and energy disorder are systematically summarized and reviewed, including crystallization optimization, defect passivation, and interface engineering. Finally, the authors offer an overall perspective on managing Eloss in IPSCs and point out the possible ways to reduce the Eloss and promote the efficiency. This review provides a basic understanding of Eloss and may inspire new designs or more impactful methods for further minimizing the Eloss of IPSCs.

Enhanced Electrons Extraction of Lithium-Doped SnO$_{2}$ Nanoparticles for Efficient Planar Perovskite Solar Cells

Hybrid lead halide perovskite solar cells (PSCs) are amongst those efficient solar cell technologies which are developing rapidly. The rapid advancement in PSCs technology is because of favorable properties of perovskite materials and addition of charge selective layers. Here, we report lithium-doped SnO $_{2}$ electron transport layer (ETL) to improve electrons extraction from the perovskite absorbing layer. The lithium-doped SnO $_{2}$ not only shows relatively higher conductivity, reduced oxygen-deficient regions, improved oxidation state, but also induces a larger grain size of perovskite films. This leads to an improvement in all related photovoltaic parameters of the methylammonium lead iodide (MAPbI3) planar heterojunction PSCs. The champion device yields a power conversion efficiency of 19.09%. The simple solution and lower annealing processed ETLs are compatible with almost all substrates used in PSCs and other perovskite-based devices.

Green fabrication of stable lead-free bismuth based perovskite solar cells using a non-toxic solvent

The very fast evolution in certified efficiency of lead-halide organic-inorganic perovskite solar cells to 24.2%, on par and even surpassing the record for polycrystalline silicon solar cells (22.3%), bears the promise of a new era in photovoltaics and revitalisation of thin film solar cell technologies. However, the presence of toxic lead and particularly toxic solvents during the fabrication process makes large-scale manufacturing of perovskite solar cells challenging due to legislation and environment issues. For lead-free alternatives, non-toxic tin, antimony and bismuth based solar cells still rely on up-scalable fabrication processes that employ toxic solvents. Here we employ non-toxic methyl-acetate solution processed (CH3NH3)3Bi2I9 films to fabricate lead-free, bismuth based (CH3NH3)3Bi2I9 perovskites on mesoporous TiO2 architecture using a sustainable route. Optoelectronic characterization, X-ray diffraction and electron microscopy show that the route can provide homogeneous and good quality (CH3NH3)3Bi2I9 films. Fine-tuning the perovskite/hole transport layer interface by the use of conventional 2,2′,7,7′-tetrakis (N,N′-di-p-methoxyphenylamino)−9,9′-spirbiuorene, known as Spiro-OMeTAD, and poly(3-hexylthiophene-2,5-diyl - P3HT as hole transporting materials, yields power conversion efficiencies of 1.12% and 1.62% under 1 sun illumination. Devices prepared using poly(3-hexylthiophene-2,5-diyl hole transport layer shown 300 h of stability under continuous 1 sun illumination, without the use of an ultra violet-filter.

A High Mobility Conjugated Polymer Enables Air and Thermally Stable CsPbI2Br Perovskite Solar Cells with an Efficiency Exceeding 15%

AbstractInorganic cesium lead halide perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with a power conversion efficiency of over 16%. However, CsPbI2Br is known to be very sensitive to moisture, and the intrinsic long‐term stability of CsPbI2Br film remains a critical challenge. Interface engineering has been proven to be an effective way for solving the instability‐to‐moisture issue and enhancing the performance of inorganic–organic hybrid PSCs, while there are a few reports on interface engineering for inorganic PSCs. Here, a conjugated polymer, poly(N‐alkyldiketopyrrolo‐pyrrole dithienylthieno[3,2‐b]thio‐phene) (DPP‐DTT), with high mobility is introduced as a novel interface passivation for CsPbI2Br PSCs, which can significantly reduce nonradiative recombination in perovskite, leading to significant enhancement in both efficiency and stability of CsPbI2Br PSCs. Through DPP‐DTT passivation, a champion efficiency of 15.14% is obtained in CsPbI2Br PSCs. Moreover, the Lewis base DPP‐DTT can serve as an ultrahydrophobic agent to hold the photovoltaic performance of CsPbI2Br PSCs under ambient environment with humidity or thermal stress. These results provide a simple while highly effective route of fabricating the highly efficient and stable inorganic PSCs.

Growth of Amorphous Passivation Layer Using Phenethylammonium Iodide for High‐Performance Inverted Perovskite Solar Cells

Organic–inorganic lead halide perovskite solar cells have realized a rapid increase of power conversion efficiency (PCE) in the past few years. However, their performance still suffers trap‐assisted decline due to defects at the surface and grain boundaries of the perovskite film. Herein, a phenethylammonium iodide‐lead iodide (PEAI‐PbI2) passivation layer is formed on the CH3NH3PbI3 perovskite film. The characterization results indicate that the PEAI covering layer leads to the reduction of surface defects and suppression of nonradiative recombination. By manipulating this surface passivation method, a remarkably improved VOC of 1.16 V and an enhanced PCE of 20.8% are achieved.