Perovskite-based Photovoltaics Research Articles

Artificial Perovskite Multiple Quantum Well Optoelectronics

Metal halide perovskite-based photovoltaics and light-emitting diodes (LEDs) have exhibited a promising trajectory toward commercial viability, nearing the performance levels of them to the commercially established materials. A particularly encouraging avenue involves tailoring the various dimensions of perovskite materials, notably through the implementation of perovskite multiple quantum wells (MQWs), to amplify their potential in optoelectronic applications. This comprehensive review delves into recent breakthroughs in both self-assembled perovskite MQWs and artificially fabricated counterparts, elucidating their mechanisms and performance characteristics. By gathering and evaluating the very original and the latest research findings, this review aims to provide valuable insights into the underlying principles governing optical behaviors of perovskite MQWs as well as optoelectronic and photonic applications. Furthermore, it outlines prospective research pathways, delineating potential pathways for further exploration and optimization of perovskite MQW-based devices. Through this general evaluation on the recent advancements and prospects, this review contributes to advancing the understanding and application of perovskite materials in next-generation optoelectronic and photonic technologies.

Flexible Indoor Perovskite Solar Cells by In Situ Bottom-Up Crystallization Modulation and Interfacial Passivation.

A robust perovskite-buried interface is pivotal for achieving high-performance flexible indoor photovoltaics as it significantly influences charge transport and extraction efficiency. Herein, a molecular bridge strategy is introduced utilizing sodium 2-cyanoacetate (SZC) additive at the perovskite-buried interface to simultaneously achieve in situ passivation of interfacial defects and bottom-up crystallization modulation, resulting in high-performance flexible indoor photovoltaic applications. Supported by both theoretical calculations and experimental evidences, it illustrates how SZCs serve as molecular bridges, establishing robust bonds between SnO2 transport layer and perovskite, mitigating oxygen vacancy defects and under-coordinated Pb defects at interface during flexible fabrication. This, in turn, enhances interfacial energy level alignment and facilitates efficient carrier transport. Moreover, this in situ investigation of perovskite crystallization dynamics reveals bottom-up crystallization modulation, extending perovskite growth at the buried interface and influencing subsequent surface recrystallization. This results in larger crystalline grains and improved lattice strain of the perovskite during flexible fabrication. Finally, the optimized flexible solar cells achieve an impressive efficiency exceeding 41% at 1000 lux, with a fill factor as high as 84.32%. The concept of the molecular bridge represents a significant advancement in enhancing the performance of perovskite-based flexible indoor photovoltaics for the upcoming era of Internet of Things (IoT).

Vapor phase deposition of perovskite photovoltaics: short track to commercialization?

While perovskite-based photovoltaics is progressing toward commercialization, it remains an open question which fabrication technology – solution-based, vapor-based, or combinations – will pave the way to faster economic breakthrough.

Ga and In-based hybrid halide perovskites as an alternative to Pb: a first principles study.

Lead-free hybrid halide perovskites have gained much attention in the field of photovoltaics due to their non-toxicity, stability and unique photo-physical properties. Sn and Ge-based ABX3 perovskites have been widely studied due to their similar electronic properties to Pb-based materials. However, the unstable oxidation state of Sn is a major challenge for the commercialization of this class of materials. To overcome this problem, here, we have designed a series of novel Ga and In-based A3B2X9-type perovskite materials incorporating the methylammonium (MA) organic cation in the A site and I- as the halide ion in the X site. In this regard, we have investigated different structural, electronic, optical and photovoltaic properties by employing the density functional theory formalism. The formation of a stable three dimensional perovskite structure is determined by the observed values of tolerance factor (TF) and octahedral factor (μ). The observed negative values of formation enthalpy manifest that our studied materials are also thermodynamically stable. The obtained band gap values reveal that our designed perovskite materials can act as semiconducting materials for application in photovoltaics. We have also investigated the optical properties of our studied materials and the observed values of dielectric function and absorption coefficient in the visible range of the electromagnetic spectrum indicate their excellent photo absorption. The observed theoretical power conversion efficiency (PCE) values reveal that (MA)3In2I9 (13.82%) and (MA)3 (Ga.50In.50)2I9 (12.8%) can be chosen as potential candidates for application in perovskite-based photovoltaics. This research provides a pathway for the development of less toxic and efficient semiconducting materials, offering exciting prospects for their utilization in optoelectronics and contributing to the ongoing efforts to advance sustainable energy technologies.

Optical modeling and active layer design of MASnI3 perovskite photovoltaics using finite-difference time-domain simulation: from the sun to indoor light

We investigated the optoelectronic effect of MASnI3 perovskite-based photovoltaics by designing an active layer using the finite-difference time-domain simulation. AM 1.5 G was chosen as the solar light source, set to provide the 400–900 nm wavelength region. As an active layer design method, we controlled the active layer thickness from 20 to 200 nm with a 20 nm step. As the active layer thickness became thicker, J sc rose sharply and became saturated, and when it was 200 nm, J sc was highest at 25.64 mA cm−2. Furthermore, we solved the electric field intensity distribution for each wavelength of light according to the active layer thickness. Finally, by calculating J sc according to the active layer thickness and generation rate of the optimal device under indoor light sources, we were able to extend our research to indoor applications.

Efficient and reliable encapsulation for perovskite/silicon tandem solar modules.

Perovskite/silicon tandem solar cells have a tremendous potential to boost renewable electricity production thanks to their very high performance combined with promising cost structure. However, for actual field deployment, any solar cell technology needs to be assembled into modules, where the associated processes involve several challenges that may affect both the performance and stability of the devices. For instance, due to its hygroscopic nature, ethylene vinyl acetate (EVA) is incompatible with perovskite-based photovoltaics. To circumvent this issue, we investigate here two alternative encapsulant polymers for the packaging of perovskite/silicon tandems into minimodules: a thermoplastic polyurethane (TPU) and a thermoplastic polyolefin (TPO) elastomer. To gauge their impact on tandem-module performance and stability, we performed two internationally established accelerated module stability tests (IEC 61215): damp heat exposure and thermal cycling. Finally, to better understand the thermomechanical properties of the two encapsulants and gain insight into their relation to the thermal cycling of encapsulated tandems, we performed a dynamic mechanical thermal analysis. Our understanding of the packaging process of the tandem module provides useful insights for the development of commercially viable perovskite photovoltaics.

Solid-State Nuclear Magnetic Resonance of Triple-Cation Mixed-Halide Perovskites.

Mixed-cation lead mixed-halide perovskites are the best candidates for perovskite-based photovoltaics, thanks to their higher efficiency and stability compared to the single-cation single-halide parent compounds. TripleMix (Cs0.05MA0.14FA0.81PbI2.55Br0.45 with FA = formamidinium and MA = methylammonium) is one of the most efficient and stable mixed perovskites for single-junction solar cells. The microscopic reasons why triple-cation perovskites perform so well are still under debate. In this work, we investigated the structure and dynamics of TripleMix by exploiting multinuclear solid-state nuclear magnetic resonance (SSNMR), which can provide this information at a level of detail not accessible by other techniques. 133Cs, 13C, 1H, and 207Pb SSNMR spectra confirmed the inclusion of all ions in the perovskite, without phase segregation. Complementary measurements showed a peculiar longitudinal relaxation behavior for the 1H and 207Pb nuclei in TripleMix with respect to single-cation single-halide perovskites, suggesting slower dynamics of both organic cations and halide anions, possibly related to the high photovoltaic performances.

Tin oxide/reduced graphene oxide hybrid as a hole blocking layer for improving 2D/3D hetrostructured perovskite-based photovoltaics

Perovskite photovoltaics have appeared as a promising technology for new-generation photovoltaics. Developing a hole blocking layer (HBL) has also proven to be a successful method of enhancing the efficiency of perovskite solar cells (PSCs). Hereof, planar 3D/2D structured devices are developed using a reduced graphene oxide (rGO) modified tin oxide (SnO2). The results show that the modified HBL can improve perovskite crystallization, optical absorption, and passivate interface trap-defect at the perovskite/SnO2 interface. The modification impact accounts for the improvement of charge transfer and better work function alignment of SnO2. When an optimized 3% rGO additive was incorporated into the SnO2 layer, the PSC exhibited the champion performance in short-current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) of the PSCs, which were 24.11 mA/cm2, 1.093 V, and 79.64%, respectively, and the efficiency was boosted from 16.48% to 20.98%. This HBL modification route allows for defect passivation, which improves the performance of perovskite photovoltaics even more.

Solvent-Free Method for Defect Reduction and Improved Performance of p-i-n Vapor-Deposited Perovskite Solar Cells.

As perovskite-based photovoltaics near commercialization, it is imperative to develop industrial-scale defect-passivation techniques. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal-halide perovskite thin films. We demonstrate markably improved growth and optoelectronic properties for vapor-deposited [CH(NH2)2]0.83Cs0.17PbI3 perovskite solar cells by partially substituting PbI2 for PbCl2 as the inorganic precursor. We find the partial substitution of PbI2 for PbCl2 enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yields by more than an order of magnitude, and charge-carrier mobility from 46 cm2/(V s) to 56 cm2/(V s). This results in improved solar-cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI2 for PbCl2. Our method presents a scalable, dry, and solvent-free route to reducing nonradiative recombination centers and hence improving the performance of vapor-deposited metal-halide perovskite solar cells.

Electrodeposition as a Versatile Preparative Tool for Perovskite Photovoltaics: Aspects of Metallization and Selective Contacts/Active Layer Formation

Perovskite‐based photovoltaics (PV) is expected to play a central role in sustainable energy production during the next decades. Several companies are investing intensively to develop a market‐ready product with efficiency and stability rapidly improving. The craft of making perovskite solar cells (PSCs) consists in the art of thin‐film deposition, with electrodeposition (ED) representing one of the most versatile techniques available. The ED's role in the development of perovskite PV with its advantages, drawbacks, and perspectives is analyzed herein. The ED of inorganic or organic/polymeric selective contacts enables high‐efficiency devices. Moreover, by exploiting properly designed functional barriers it is possible to rely on ED for the metallization of perovskite solar cells through the deposition of copper. The latter aspect could be particularly relevant for the development of silicon/perovskite tandem PV at the TW scale. On the other hand, the ED of the active layer is less successful to date mainly due to solubility issues of the perovskite in electrochemical polar solvents.

Introduction of γ-butyrolactone (GBL) solvent to assist perovskite crystallization and develop stable and efficient perovskite solar cells

Researchers' admiration for perovskite materials and their efforts to develop of perovskite-based photovoltaics every day make the world near to the industrialization of perovskite solar cells (PSCs). Interface engineering, which as a practical and effective approach to tailor the interface of perovskite and Hole transport layer (HTL) has been introduced to fabricate efficient and stable PSCs, herein is employed through the addition of γ-butyrolactone (GBL) into the anti-solvent solution. Since, the GBL solvent was added into the chlorobenzene (CBZ) as anti-solvent, in different volume ratios to improve crystallization of perovskite layer, and brings us a simple interface engineering at perovskite/HTL. Results showed with the addition of GBL into the CB anti-solvent a perovskite layer with fewer pinholes is achieved. The anti-solvent engineering enlarged perovskite grain sizes and passivated grain boundaries. It was observed that our approach, reduced carriers' traps in the perovskite film and charge inhibit recombination processes within PSCs. The boosted crystalline properties of the treated perovskite layer, the facilitated charges extraction at perovskite/HTL interface and the reduce charge accumulation brings a champion efficiency of 18.97% for the modified devices higher than that of 15.21% for the unmodified devices. In addition, due to the boosted hydrophobic property of the modified perovskite layer, the stability behavior of the related PSCs improved.

Dynamic Exciton Polaron in Two-Dimensional Lead Halide Perovskites and Implications for Optoelectronic Applications.

ConspectusThe past few years have witnessed an exciting revival of the research interest in two-dimensional (2D) lead halide perovskites. The renaissance is strongly motivated by the great success of their three-dimensional (3D) counterparts in optoelectronic applications. Different from 3D lead halide perovskites where free carriers are generated upon photoexcitation, 2D lead halide perovskites experience weaker dielectric screening and stronger quantum confinement effects. Therefore, strongly bound excitons with binding energy of up to a few hundreds of meV are considered to be the main excited-state species responsible for optoelectronic processes in 2D perovskites. In addition to strong excitonic effects, polaronic effects are also inherent in the soft and anharmonic lattice of lead halide perovskites, and polaronic structural relaxation is found to strongly renormalize carrier excited-state behaviors. For example, ferroelectric large polaron formation and liquid-like solvation of band edge carriers are proposed to account for the exceptional properties of 3D lead halide perovskites. As for 2D lead halide perovskites, polaronic characteristics have also been observed in exciton spectral characters, but how the interplay between excitonic effect and polaronic effect redefines the nature of exciton polarons and their excited-state behaviors still remains largely unexplored.In this Account, we discuss our recent experimental findings about the excited-state properties of exciton polarons in 2D lead halide perovskites. We begin our discussion by introducing a conventional view of strongly bound excitons in 2D lead halide perovskites with large exciton binding energy, which is typically estimated from steady-state absorption spectra. However, owing to the soft and anharmonic lattice, excitons in 2D lead halide perovskites exhibit significant polaronic characters and exist as exciton polarons. It is still unclear how polaronic effects would affect the exciton properties in 2D lead halide perovskites, especially in their excited-state dynamics. By probing exchange interaction, we found that both intra- and inter-exciton Coulomb interaction strengths are substantially weakened by the polaronic screening effect, which is manifested as (1) a counterintuitively longer exciton spin lifetime by almost an order of magnitude or a smaller intraexcitonic interaction strength with temperature increasing from 80 to 340 K and (2) an order of magnitude smaller interexcitonic interaction strength compared to another prototypical 2D semiconductor named transition-metal dichalcogenides (TMDCs) with a comparable steady-state exciton binding energy. We further discuss the interplay between the long- and short-range exciton-phonon interaction and conclude that the exciton-phonon interaction strength is in an intermediate regime and the exciton polaron is momentarily trapped in 2D perovskites, that is, a dynamic exciton polaron.Finally, we highlight prospective opportunities with ligand and cation engineering to regulate the exciton-phonon interaction and exciton polaron properties in 2D perovskites, which have strong implications toward future rational design for 2D perovskite-based efficient photovoltaics or light-emitting devices with high color purity.

Surface-Passivated CsPbBr3 for Developing Efficient and Stable Perovskite Photovoltaics

All-inorganic perovskites consisting of only inorganic elements have been recently considered as highly stable semiconductors for photoactive layer of optoelectronics applications. However, the formation of high-quality thin film and trap-reduced interface has still remains an important task, which should be solved for improving the performances of all-inorganic perovskite-based photovoltaics. Here, we adopted facile method that could reduce charge-carrier recombination by depositing a passivation agent on the top surface of the CsPbBr3 all-inorganic perovskite layer. We also found that the CsPbBr3 perovskite photovoltaic prepared from surface treatment method using n-octylammonium bromide provides an improved stability in ambient environment and 1-sun illuminating condition. Therefore, the perovskite photovoltaics fabricated from our approach offered an improved power conversion efficiency of 5.44% over that of the control device without surface treatment (4.12%).

Proton‐Radiation Tolerant All‐Perovskite Multijunction Solar Cells (Adv. Energy Mater. 41/2021)

Photovoltaics In article number 2102246 Felix Lang, Giles E. Eperon, Samuel D. Stranks and co-workers investigate efficient all perovskite-based tandem photovoltaics. This class of photovoltaics combine high specific power with good tolerance to the harsh radiation environment in space, thereby promising a next-generation of lightweight and cost-efficient solutions to power private space exploration, low-cost missions as well as future habitats on the Moon and Mars.

Tailoring hot carrier cooling and recombination dynamics of mixed halide perovskite by incorporating Au@CZTS core–shell nanocrystal

Organic–inorganic halide perovskite has emerged as the front-runner of absorber materials for highly efficient solar cell in recent years. The incorporation of metallic (Au, Ag) nanoparticles (NPs) within the perovskite contributes to the effective tuning of their optoelectronic properties via enhancing the channels of solar energy transfer and promoting carrier transport. Placing a dielectric shell over the metal NP further enhances the carrier mobility and reduces the carrier recombination in the semiconductor material. Here, we have extensively investigated the effect of the Au@CZTS core–shell nanocrystal (NC) on hot carrier (HC) cooling dynamics and excited carrier recombination dynamics in bulk MAPbI3−X Cl X perovskite using femtosecond transient absorption spectroscopy with a temporal and spectral resolution of 120 fs and 0.8 nm respectively. The HC cooling dynamics indicates the formation of longitudinal optical (LO) phonons within the first 0.6 ps and a delayed conversion of LO phonons to longitudinal acoustic (LA) phonons from 8 ps to 15.9 ps due to the incorporation of the Au@CZTS core–shell NC in bulk perovskite. Further, the investigation of carrier recombination dynamics shows that at a fixed pump fluence of 3.19 μJ cm −2 the rate constants decrease nearly 1 order of magnitude for (a) Auger recombination (from 1.2 × 10−32 cm6 s−1 to 1.7 × 10−34 cm6 s−1), (b) band-to-band recombination (from 8 × 10−14 cm3 s−1 to 8 × 10−15 cm3 s−1) and (c) trap state recombination (from 5.5 × 108 μs−1 to 5 × 107 μs−1) after the modification of bulk perovskite by Au@CZTS core–shell NC. Delayed conversion of LO phonons to LA phonons confirms the presence of an enhanced ‘hot phonon bottleneck’ effect in modified bulk perovskite. Lowering of the recombination rate constants provides an opportunity for developing high-performance perovskite-based photovoltaics.

Improving the Morphology Stability of Spiro-OMeTAD Films for Enhanced Thermal Stability of Perovskite Solar Cells.

To guarantee a long lifetime of perovskite-based photovoltaics, the selected materials need to survive relatively high-temperature stress during the solar cell operation. Highly efficient n-i-p perovskite solar cells (PSCs) often degrade at high operational temperatures due to morphological instability of the hole transport material 2,2',7,7'-tetrakis (N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (Spiro-OMeTAD). We discovered that the detrimental large-domain spiro-OMeTAD crystallization is caused by the simultaneous presence of tert-butylpyridine (tBP) additive and gold (Au) as a capping layer. Based on this discovery and our understanding, we demonstrated facile strategies that successfully stabilize the amorphous phase of spiro-OMeTAD film. As a result, the thermal stability of n-i-p PSCs is largely improved. After the spiro-OMeTAD films in the PSCs were stressed for 1032 h at 85 °C in the dark in nitrogen environment, reference PSCs retained only 22% of their initial average power conversion efficiency (PCE), while the best target PSCs retained 85% relative average PCE. Our work suggests facile ways to realize efficient and thermally stable spiro-OMeTAD containing n-i-p PSCs.

A new CASE for complementary materials science categorization

A new CASE for complementary materials science categorization

Manipulated Crystallization and Passivated Defects for Efficient Perovskite Solar Cells via Addition of Ammonium Iodide

Organic-inorganic metal halide perovskite materials have been widely studied as the light absorber for efficient photovoltaics. However, perovskite layers with defective nature are typically prepared with an uncontrollable crystallization process, intrinsically limiting further advance in device performance, and thus require delicate manipulation of crystallization processes and defect density. Here, we demonstrate an ammonium-assisted crystallization of perovskite absorbers during a two-step deposition to fabricate efficient solar cells. Addition of ammonium iodide (NH4I) is devised to manipulate the nucleation and crystal growth of perovskite, wherein the formation and transition of intermediate x[NH4+]•[PbI3]x- enables high-quality perovskite layers with an enlarged grain and reduced defect density. As a result, the perovskite solar cells (PSCs) achieve an average efficiency of 21.36% with a champion efficiency of 22.15% and improved environmental stability over 30 days in ambient conditions with varied relative humidity. These results with addition of NH4I provide an available and ingenious way to construct high-quality perovskite layers for efficient solar cells and will advance the commercial application of perovskite-based photovoltaics.

Discovery of temperature-induced stability reversal in perovskites using high-throughput robotic learning

Stability of perovskite-based photovoltaics remains a topic requiring further attention. Cation engineering influences perovskite stability, with the present-day understanding of the impact of cations based on accelerated ageing tests at higher-than-operating temperatures (e.g. 140°C). By coupling high-throughput experimentation with machine learning, we discover a weak correlation between high/low-temperature stability with a stability-reversal behavior. At high ageing temperatures, increasing organic cation (e.g. methylammonium) or decreasing inorganic cation (e.g. cesium) in multi-cation perovskites has detrimental impact on photo/thermal-stability; but below 100°C, the impact is reversed. The underlying mechanism is revealed by calculating the kinetic activation energy in perovskite decomposition. We further identify that incorporating at least 10 mol.% MA and up to 5 mol.% Cs/Rb to maximize the device stability at device-operating temperature (<100°C). We close by demonstrating the methylammonium-containing perovskite solar cells showing negligible efficiency loss compared to its initial efficiency after 1800 hours of working under illumination at 30°C.

Wide-Bandgap Halide Perovskites for Indoor Photovoltaics.

Indoor photovoltaics (IPVs) are receiving great research attention recently due to their projected application in the huge technology field of Internet of Things (IoT). Among the various existing photovoltaic technologies such as silicon, Cadmium Telluride (CdTe), Copper Indium Gallium Selenide (CIGS), organic photovoltaics, and halide perovskites, the latter are identified as the most promising for indoor light harvesting. This suitability is mainly due to its composition tuning adaptability to engineer the bandgap to match the indoor light spectrum and exceptional optoelectronic properties. Here, in this review, we are summarizing the state-of-the-art research efforts on halide perovskite-based indoor photovoltaics, the effect of composition tuning, and the selection of various functional layer and device architecture onto their power conversion efficiency. We also highlight some of the challenges to be addressed before these halide perovskite IPVs are commercialized.