Solid-state Perovskite Solar Cells Research Articles

Additive engineering for highly efficient and stable perovskite solar cells

Since the groundbreaking report on solid-state perovskite solar cells (PSCs) in 2012, PSC receives great attention due to its high power conversion efficiency (PCE) obtainable at low-cost fabrication. A PCE of 9.7% in 2012 was swiftly improved to 25.7% in 2022 via perovskite composition engineering and grain size control. The excellent photovoltaic performance originates from the defect-tolerant property of organic lead halide perovskite associated with the antibonding nature of the valence band. Nevertheless, the reduction of defect-induced trap density of the state is still required to improve further photovoltaic performance and stability. Among the methods reported to reduce defects, additive engineering is one of the promising strategies for controlling crystallographic defects because it can regulate crystallization kinetics and grain boundaries. In this review, we describe materials and methods for additive engineering applied to lead-based perovskite. In addition, the effects of additive engineering on photovoltaic performance and stability are discussed.

A Review on Recent Advances in Materials of Hybrid Organic–Inorganic Perovskite Solar Cells

This study is an emphasis on the metal halide perovskite solar cells that are susceptible to factors that influence their power conversion efficiency (PCE). Perovskite solar cells, also known as PSCs, have been shown to have a high power conversion efficiency (PCE) due to a number of various factors. As they reached a power conversion efficiency of 25%, solar cells based on metal halide perovskite were a game-changer in the quest for photovoltaic performance. A flurry of activity in the fields of structure design, materials chemistry, process engineering, and device physics has helped the solid-state perovskite solar cell to become a leading contender for the next generation of solar energy harvesters in the world today. This follows up on the ground-breaking development of the solid-state perovskite solar cell in 2012. This cell has a higher efficiency compared to commercial silicon or other organic and inorganic solar cells, as well as a lower cost of materials and processes. However, it has the disadvantage that these high efficiencies can only be obtained with lead-based perovskites, which increases the cost of the cell. As a result of this fact, a new study area on lead-free metal halide perovskites was established, and it is now exhibiting a remarkable degree of vibrancy. This provided us with the impetus to review this burgeoning area of research and discuss possible alternative elements according to current theoretical and practical investigations that might be utilized to replace lead in metal halide perovskites as well as the features of the perovskite materials that correspond to these elements.

Paradoxical Approach with a Hydrophilic Passivation Layer for Moisture-Stable, 23% Efficient Perovskite Solar Cells

Since the first report on the ∼10% efficient solid-state perovskite solar cell (PSC) in 2012, perovskite photovoltaics surged swiftly. Although there has been a quantum leap in the power conversion...

High-Efficiency Perovskite Solar Cells.

With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.

Graphene doped with silver nanoparticle as p-type dopants in efficient perovskite solar cells

Perovskite materials have been shown to be involved in energy conversion and environmental applications. Graphene doped with silver nanoparticle (Ag@G) is designed and synthesized for the first time as p-type dopants in solid-state perovskite solar cells (PSCs) applications. The fabricated nanocomposite was emphasized by X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM). By characterizing the optical and electrochemical properties, graphene doped with silver nanoparticles is eligible for oxidation of N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis(4-methoxyphenyl)-9,9′-spirobi[9H-fluorene]-2,2′,7,7′-tetramine (Spiro-OMeTAD), the commonly used hole-transport material (HTM). The results revealed that the Ag@G nanocomposite was successfully synthesize. Furthermore, the efficiency of PSCs as high as 10 percent was achieved when the prepared material was applied as a p-type. This could be attributed to the boosting of the charge carrier transfer between the absorbing layer and the fabricated material. Therefore, the fabricated Ag@G nanocomposite is a promising candidate for a solar cell technology as a p-type dopant.

Maximizing Short Circuit Current Density and Open Circuit Voltage in Oxygen Vacancy-Controlled Bi1-xCaxFe1-yTiyO3-δ Thin-Film Solar Cells.

Designing solid-state perovskite oxide solar cells with large short circuit current (JSC) and open circuit voltage (VOC) has been a challenging problem. Epitaxial BiFeO3 (BFO) films are known to exhibit large VOC (>50 V). However, they exhibit low JSC (≪μA/cm2) under 1 Sun illumination. In this work, taking polycrystalline BiFeO3 thin films, we demonstrate that oxygen vacancies (VO) present within the lattice and at grain boundary (GB) can explicitly be controlled to achieve high JSC and VOC simultaneously. While aliovalent substitution (Ca2+ at Bi3+ site) is used to control the lattice VO, Ca and Ti cosubstitution is used to bring out only GB-VO. Fluorine-doped tin oxide (FTO)/Bi1-xCaxFe1-yTiyO3-δ/Au devices are tested for photovoltaic characteristics. Introducing VO increases the photocurrent by four orders (JSC ∼ 3 mA/cm2). On the contrary, VOC is found to be <0.5 V, as against 0.5-3 V observed for the pristine BiFeO3. Ca and Ti cosubstitution facilitate the formation of smaller crystallites, which in turn increase the GB area and thereby the GB-VO. This creates defect bands occupying the bulk band gap, as inferred from the diffused reflection spectra and band structure calculations, leading to a three-order increase in JSC. The cosubstitution, following a charge compensation mechanism, decreases the lattice VO concentration significantly to retain the ferroelectric nature with enhanced polarization. It helps to achieve VOC (3-8 V) much larger than that of BiFeO3 (0.5-3 V). It is noteworthy that as Ca substitution maintains moderate crystallite size, the lattice VO concentration dominates GB-VO concentration. Notwithstanding, both lattice and GB-VO contribute to the increase in JSC; the former weakens ferroelectricity, and as a consequence, undesirably, VOC is lowered well below 0.5 V. Using optimum JSC and VOC, we demonstrate that the efficiency ∼0.22% can be achieved in solid-state BFO solar cells under AM 1.5 one Sun illumination.

Scalable fabrication and coating methods for perovskite solar cells and solar modules

Since the report in 2012 of a solid-state perovskite solar cell (PSC) with a power-conversion efficiency (PCE) of 9.7% and a stability of 500 h, intensive efforts have been made to increase the certified PCE, reaching 25.2% in 2019. The PCE of PSCs now exceeds that of conventional thin-film solar-cell technologies, and the rate at which this increase has been achieved is unprecedented in the history of photovoltaics. Moreover, the development of moisture-stable and heat-stable materials has increased the stability of PSCs. Small-area devices ( 100 cm2) substrates required for commercialization. Thus, materials and methods need to be developed for coating large-area PSCs. In this Review, we discuss solution-based and vapour-phase coating methods for the fabrication of large-area perovskite films, examine the progress in performance and the parameters affecting the properties of large-area coatings, and provide an overview of the methodologies for achieving high-efficiency perovskite solar modules. The scalable fabrication of perovskite solar cells and solar modules requires the development of new materials and coating methods. In this Review, we discuss solution-based and vapour-phase coating methods for large-area perovskite films and examine the progress in performance and the parameters affecting large-area coatings.

High Efficiency Perovskite Solar Cells: Materials and Devices Engineering

Since the first report on 9.7% efficient solid-state perovskite solar cell (PSC) in 2012, perovskite photovoltaics received tremendous attentions. Efforts to increase power conversion efficiency (PCE) have been continuously made. As a result, a record PCE of 25.2% was certified in 2019, which surpassed those achieved from the conventional solar cells based on CIGS and CdTe. The superb photovoltaic performance of PSC is related to the defect-tolerant property, the long carrier lifetime, the long diffusion length of photo-generated carriers, and the high absorption coefficient. In this review, materials and devices engineering are described for achieving stability and higher PCE in PSCs. From the practical point of view, key technologies for materials, coating, and device fabrication are described, which is expected to be helpful to achieve high efficiency PSCs. Moreover, interfacial engineering methodologies toward hysteresis-less and stable PSCs are also presented to give insight into better understanding ion migration and recombination in PSCs.

Conductive glass free carbon nanotube micro yarn based perovskite solar cells

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology on the lab scale due to their high power conversion efficiency, simple device fabrication, all solid-state structure and the possibility to integrate traditional devices into fiber format. In this work, a three-dimensional (3D) perovskite solar cell is demonstrated using functionalized carbon nanotube (CNT) yarn as both the cathode and anode material. TiO2 and 2,2,7,-7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) are used as the electron transporting and hole transporting material respectively. The TiO2 oxide layer is deposited on the top of the twisted carbon nanotube yarn and annealed with TiCl4 to generate the uniform electron transport layer. A dip coating process is employed to produce a uniform perovskite layer on top of the TiO2 oxide layer. Platinized carbon nanotube yarn is wrapped around on the top of the hole transporting layer and serves as the counter electrode. The photovoltaic characterization of the prepared cells was carried out at different cell lengths. Under AM 1.5 (100 mW cm−2) illumination it shows an enhanced power conversion efficiency (PCE) with a high open current voltage (VOC) of 0.825 V. This three-dimensional all solid-state perovskite solar cell shows a promising prospect in portable and wearable textile electronics.

Comparative Studies on the Efficiency, Reproducibility and Stability of Perovskite Solar Cells

Abstract In literature, many studies based on planar inverted structure using either CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite absorbers have reported as high-efficiency solid-state perovskite solar cells. This study includes the comparison of photovoltaic characterizations, reproducibility and stability results of solar cells fabricated by using CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite compounds. Herein, the results showed that CH3NH3PbI3 perovskite solar cells gave a lower photovoltaic performance as-fabricated when compared with CH3NH3PbI3-xClx perovskite solar cells. However, after 24 hours, CH3NH3PbI3 perovskite compound showed a higher photovoltaic performance and better time stability in inert atmosphere and more reproducible results

Electrosprayed Polymer-Hybridized Multidoped ZnO Mesoscopic Nanocrystals Yield Highly Efficient and Stable Perovskite Solar Cells.

Solid-state perovskite solar cells have been expeditiously developed since the past few years. However, there are a number of open questions and issues related to the perovskite devices, such as their long-term ambient stability and hysteresis in current density–voltage curves. We developed highly efficient and hysteresis-less perovskite devices by changing the frequently used TiO2 mesoscopic layer with polymer-hybridized multidoped ZnO nanocrystals in a common n–i–p structure for the first time. The gradual adjustment of ZnO conduction band position using single- and multidopant atoms will likely enhance the power conversion efficiency (PCE) from 8.26 to 13.54%, with PCEmax = 15.09%. The highest PCEavg of 13.54% was demonstrated by 2 atom % boron and 6 atom % fluorine co-doped (B, F:ZnO) nanolayers (using optimized film thickness of 160 nm) owing to their highest conductivity, carrier concentration, optical transmittance, and band-gap energy compared to other doped films. We also successfully apply a fine polyethylenimine thin layer on the doped ZnO nanolayers, causing the reduction in work function and overall demonstrating the enhancement in PCE from ∼10.86% up to 16.20%. A polymer-mixed electron-transporting layer demonstrates the remarkable PCEmax of 20.74% by decreasing the trap sites in the oxide layer that probably reduces the chances of carrier interfacial recombination originated from traps and thus improves the device performance. Particularly, we produce these electron-rich multidoped ZnO nanolayers via electrospray technique, which is highly suitable for the future development of perovskite solar cells.

Research Direction toward Theoretical Efficiency in Perovskite Solar Cells

The recently certified efficiency of 22.7% makes perovskite solar cells (PSCs) rise to the top among the thin film technologies of photovoltaics. The research activities of PSCs have been triggered by the ground-breaking report on a 9.7% efficient and 500 h-stable solid-state perovskite solar cell employing methylammonium lead iodide adsorbed on mesoporous TiO2 film and an organic hole conducting layer in 2012. However, PSCs are facing issues on stability, current–voltage hysteresis, ion migration, and so on, which should be solved for commercialization. In addition, further improvement in power conversion efficiency is still needed for PSCs. In this Perspective, the Shockley–Queisser (S-Q) limit in PSCs is investigated, where the best performing state-of-the-art PSC is used for this study. Short-circuit photocurrent density (Jsc) is found to approach the S-Q limit, while open-circuit voltage (Voc) and fill factor (FF) are far below their S-Q limits. Thus, toward an S-Q limit efficiency of ∼30% for PSCs w...

Halide perovskite photovoltaics: History, progress, and perspectives

Abstract

High-efficiency hole-conductor-free rutile TiO2-Nanorod/CH3NH3PbI3 heterojunction solar cells with commercial carbon ink as counter-electrode

This work demonstrates the fabrication of a high-efficiency, hole-conductor-free, solid-state perovskite solar cell with TiO2-nanorod arrays (NRAs) as photoanodes and commercial carbon ink as counter-electrodes. TiO2-NRA films of various thicknesses were deposited on FTO electrodes through hydrothermal method for different reaction durations. The effect of the thickness of TiO2-NRA films on device performance was investigated in detail. The TiO2 NRAs/CH3NH3PbI3/C devices based on 688 nm-thick TiO2-NRA films exhibited the optimal performance and power conversion efficiency (PCE) of as high as 8.56%. This value is comparable with the PCE of the recently reported TiO2 NRA/Perovskite/HTM/Au solar cell.

First-Principles Calculations of the Electronic and Optical Properties of CH3NH3PbI3 for Photovoltaic Applications

Since the first efficient solid-state perovskite solar cells were reported in 2012, rapid development of the organic-inorganic hybrid halide perovskites has been made, and a new era in optoelectronic and solar cells technologies has emerged. The unique attributes of these hybrid halide perovskites make them highly promising materials for various practical applications including high performance in converting solar energy into electrical power, with very recent results demonstrating a 20.1% efficiency. However, the electronic and optical properties of these materials at low temperature have not been investigated extensively. Herein we analyse the electronic and optical properties of methyl-ammonium lead iodide perovskite, CH3NH3PbI3, using density functional theory (DFT) and many-body perturbation theory (MBPT). The electronic band gap and energy bands of CH3NH3PbI3 have been investigated using different density functional approximations with and without the effect of the spin orbit-coupling (SOC). Depending on the calculation method, we predicted the band gap to be in the range from 0.46 eV to 2.66 eV. In order to obtain optical spectra, we carried out Bethe-Salpeter equation (BSE) calculations on top of non-self-consistent G0W0 calculations. We have presented the absorption coefficient, refractive index and reflectivity to describe optical properties of the investigated material. The phase is found to be semi-conducting with a direct band gap in the visible range of the spectrum and strong optical absorption in the visible range.

Impact of Interfacial Layers in Perovskite Solar Cells.

Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time.

Simple dopant-free hole-transporting materials with p-π conjugated structure for stable perovskite solar cells

Two simple hole-transporting materials, Me-QTPA and Me-BPZTPA, which consist of p-π conjugated structure, have been synthesized and studied in solid-state perovskite solar cells. Me-QTPA and Me-BPZTPA show outstanding thermal stabilities and appropriate HOMO levels; in addition, these two materials show wide band gaps, thus they can block the electron transport and hence suppress the carrier recombination. The solution-processed CH3NH3PbI3-based device using dopant-free Me-QTPA and Me-BPZTPA can achieve a power conversion efficiency of 9.07% and 8.16%, respectively. The perovskite solar cells with dopant-free Me-QTPA show better performance than the cells with dopant-free spiro-OMeTAD, especially in long-term stability. The power conversion efficiency for the perovskite solar cells with dopant-free Me-QTPA remains almost constant after 600h. The dopant-free Me-QTPA layer shows strong hydrophobicity with a contact angle of 101.6° to water, which indicates that Me-QTPA has a promising long-term stability at room temperature.

Cu(II) Complexes as p-Type Dopants in Efficient Perovskite Solar Cells

In this work, two Cu(II) complex compounds are designed and synthesized for applications as p-type dopants in solid-state perovskite solar cells (PSCs). Through the characterization of the optical and electrochemical properties, the complex Cu(bpcm)2 is shown to be eligible for oxidization of the commonly used hole-transport material (HTM) Spiro-OMeTAD. The reason is the electron-withdrawing effect of the chloride groups on the ligands. When the complex was applied as p-type dopant in PSCs containing Spiro-OMeTAD as HTM, an efficiency as high as 18.5% was achieved. This is the first time a Cu(II) pyridine complex has been used as p-type dopant in PSCs.

Efficient solid-state perovskite solar cells based on nanostructured zinc oxide designed by strategic low temperature water oxidation

A facile and energy saving method to produce high quality ZnO nanostructures in ultrapure water for efficient perovskite solar cells.

Nonstoichiometric Adduct Approach for High-Efficiency Perovskite Solar Cells.

Since the groundbreaking report on a solid-state perovskite solar cell employing a methylammonium lead iodide-sensitized mesoporous TiO2 film and an organic hole conducting layer in 2012 by our group, the swift surge of perovskite photovoltaics opens a new paradigm in solar-cell research. As a result, ca. 1300 peer-reviewed research articles were published in 2015. In this Inorganic Chemistry Forum on Halide Perovskite, the researches with highlights of work on perovskite solar cells in my laboratory are reviewed. We have developed a size-controllable two-step spin-coating method and found that minimal nonradiative recombination in perovskite crystals could lead to high photovoltaic performance. A Lewis acid based adduct method and self-formed grain boundary process were developed for high-efficiency devices with reproducibility. A power conversion efficiency of 20.4% was achieved via grain boundary engineering based on a nonstoichiometric adduct approach. The incorporation of cesium in a formamidinium lead iodide perovskite was found to show better photostability and moisture-stability. A reduction in the dimensionality from a three-dimensitonal nanocrystal to a one-dimensional nanowire led to a hypsochromic shift of absorption and fluorescence. To enhance the charge-carrier transport and light-harvesting efficiency, a nanoarchitecture of oxide layers was proposed.