Perovskite Deposition Methods Research Articles

How to enable highly efficient and large‐area fabrication on specific textures for monolithic perovskite/silicon tandem solar cells?

AbstractPerovskite/silicon tandem solar cells (PVSK/Si TSCs) have emerged as a promising photovoltaic technology toward achieving a high power conversion efficiency (PCE) along with cost‐effective manufacturing. The PCE of PVSK/Si TSCs has skyrocketed to a certified 33.9%, surpassing the theoretical limit of any single‐junction solar cell. This achievement is partially attributed to advancements in surface textures for Si bottom cells. In this regard, we present an overview of the recent developments concerning surface textures of Si in monolithic PVSK/Si TSCs, including planar, pyramid texture, and nanotexture. Following, the prevailing perovskite deposition methods on these textures are thoroughly discussed, and the corresponding challenges are evaluated. Additionally, we provide a summary of the advanced morphological, structural, optical, and electrical characterization techniques being utilized for theses textures. Finally, the prospects for further development of PVSK/Si TSCs are outlined, including designing novel textures with industrial compatibility, developing perovskite deposition methods with scalability, and exploring more pertinent characterization techniques for textured PVSK/Si TSCs.

Interface Effects on the Stability of Carbon‐Electrode‐Based Perovskite Solar Cells During Damp Heating

AbstractCarbon electrode‐based perovskite solar cells (C‐PSCs) are a promising innovation in solar cell technology. For their industrial development, an innovative perovskite deposition method using inkjet printing (“ink”) is compared with the more user‐friendly drop‐casting process (“drop”). Perovskite solar cells face challenges related to sensitivity to moisture and heat, prompting an investigation into their aging behavior under damp heating conditions for both deposition processes. Results reveal significant differences in aging behavior. Performance measurements demonstrate that drop‐cast solar cells have a lifetime roughly three times longer than ink‐deposited ones, despite initial similar performance. Drop‐cast solar cells exhibit an impressive lifespan of ≈3000 h. Various characterization techniques are employed to understand the role of interfaces in C‐PSC degradation. Diffraction analyses reveal structural disparities between the two cell types, while spectroscopic measurements reveal substantial degradation of charge transfer mechanisms in ink‐deposited cells, leading to pronounced radiative recombination. These findings highlight the critical influence of deposition method and active layer thickness on device stability. Optimization is imperative to achieve stable and efficient C‐PSC devices. In summary, C‐PSCs hold great promise, but their performance and longevity are intricately linked to deposition techniques and interface properties, necessitating careful engineering for practical application.

Photocatalytic Deposition of Nanostructured CsPbBr3 Perovskite Quantum Dot Films on Mesoporous TiO2 and Their Enhanced Visible-Light Photodegradation Properties.

Herein, we report the in situ photocatalytic deposition of cesium lead bromide (CsPbBr3) perovskite quantum dots on mesoporous TiO2-coated fluorine-doped tin oxide (FTO/TiO2) electrodes. The mesoporous TiO2 layer is used as a photocatalyst to promote the following: (1) the Pb deposition from a Pb2+ aqueous solution and (2) the in situ Pb conversion into CsPbBr3 perovskite in the presence of a CsBr methanolic solution without any organic capping agent. Both steps are carried out under ultraviolet light irradiation under ambient conditions without any post-treatment. The obtained FTO/TiO2/CsPbBr3 film was characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction, photoluminescence spectroscopy, scanning electron microscopy, and transmission electron microscopy. The FTO/TiO2/CsPbBr3 heterojunction exhibited enhanced visible-light photodegradation activity demonstrated for the oxidation of curcumin organic dye as a model system. The novel and simple approach to fabricating a supported photocatalyst represents a scalable general method to use semiconductors as a platform to incorporate different perovskites, either all-inorganic or hybrid, for optoelectronic applications. The perovskite deposition method mediated by the UV light at room temperature could be further applied to flexible and wearable solar power electronics.

Perovskite solar cells by vapor deposition based and assisted methods

Metal halide perovskite solar cells have made significant breakthroughs in power conversion efficiency and operational stability in the last decade, thanks to the advancement of perovskite deposition methods. Solution-based methods have been intensively investigated and deliver record efficiencies. On the other hand, vapor deposition-based and assisted methods were less studied in the early years but have received more attention recently due to their great potential toward large-area solar module manufacturing and high batch-to-batch reproducibility. In addition, an in-depth understanding of perovskite crystallization kinetics during the vapor deposition based and assisted process allows increasing perovskite deposition rate and enhancing perovskite quality. In this review, the advances in vapor-based and assisted methods for the fabrication of perovskite solar cells are introduced. The quality of the perovskite layers (i.e., morphology, crystallinity, defect chemistry, carrier lifetime) fabricated by different methods is compared. The limitations of state-of-the-art vapor-deposited perovskite layers are discussed. Finally, insights into the engineering of vapor deposition based and assisted perovskite layers toward efficient and stable perovskite solar cells and modules are provided.

Single source chemical vapor deposition (ssCVD) for highly luminescent inorganic halide perovskite films

Recent studies of lead halide perovskites demonstrate outstanding optoelectronic properties for thin-film semiconductor device application. Perovskite photovoltaic and light-emitting diodes are on the way to the mass production and spread in commercial semiconductor devices. The lab-to-fab transition of perovskite devices requires adaptation of perovskite deposition methods to industrial semiconductor fabrication standards. In this work, we demonstrated the formation of highly luminescence perovskite films by single-source chemical vapor deposition (ssCVD). Several stoichiometry compositions were prepared from inorganic precursors of CsBr and PbBr2 by dry mechanochemical synthesis with following evaporation. The combination of mechanochemical synthesis and ssCVD is an attractive approach due to the ability to scale up to industrial level and the precise control over the evaporation rate with a single source. Among all compositions CsBr:PbBr2, we show that CsPb2Br5 maintains phase composition and photoluminescent properties for powder and film. This work provides a comparative study of evaporated film properties (PL, XRD, TEM) and modeling calculations of interphase optical transitions.

Recent Progress and Challenges of Electron Transport Layers in Organic–Inorganic Perovskite Solar Cells

Organic–inorganic perovskites are crystalline light absorbers which are gaining great attraction from the photovoltaic community. Surprisingly, the power conversion efficiencies of these perovskite solar cells have rapidly increased by over 25% in 2019, which is comparable to silicon solar cells. Despite the many advances in efficiency, there are still many areas to be improved to increase the efficiency and stability of commercialization. For commercialization and enhancement of applicability, the development of electron transport layer (ETL) and its interface for low temperature processes and efficient charge transfer are very important. In particular, understanding the ETL and its interface is of utmost importance, and when this understanding has been made enough, excellent research results have been published that can improve the efficiency and stability of the device. Here, we review the progress of perovskite solar cells. Especially we discuss recent important development of perovskite deposition method and its engineering as well as the electron transport layer.

Fabrication and Degradation Analysis of Perovskite Solar Cells with Graphene Reduced Oxide as Hole Transporting Layer

Currently, the stability of perovskite solar cells (PSCs) is a critical challenge for the commercialization of such devices. A challenge in the structure of these devices is the ordinarily used hole transporting layer (HTL) which suffers from long-term instability. Considering the promised features of graphene derivatives (including their chemical resistance), we applied the graphene oxide (GO) and its reduced form (rGO) as the HTL. Also, the perovskite layer was deposited through two different routes named single-step and double-step methods. rGO was synthesized using GO through a facile procedure and deposited on the base support of the perovskite layer. Then the effect of the perovskite layer coating method and the application of GO or rGO as HTL on the stability and efficiency of the solar cell were investigated. Endurance assessments were done by running the cell for a long time at more than 1 month (720 h) in a dark environment. We achieved a power conversion efficiency (PCE) of 3.28% for perovskite solar cells which were made by a single-step perovskite deposition method with rGO as HTL. After 1 month running in an ambient atmosphere without any encapsulation, 50% of PCE was retained. The results prove that the as-prepared rGO can be an effective replacement for the common hole transporting materials for PSCs and these structures show higher performance stability compared to commonly used PEDOT: PSS as HTL.

Plasmonic hole-transport-layer enabled self-powered hybrid perovskite photodetector using a modified perovskite deposition method in ambient air

Herein, we report on an air-processed high performance self-powered hybrid perovskite (Pe) photodetector with plasmonic Silver nanoparticle (Ag NP) embedded hole-transport-layer (HTL), without the use of any electron-transporting layer (ETL). It is demonstrated that in the absence of ETL in the device, the Ag NPs embedded PEDOT:PSS HTL improves the photodetection performance significantly. We used a novel N2 gas assisted fast crystallization method for the deposition of perovskite film in ambient condition to form uniform Pe layer as compared to the nonuniform film obtained in conventional deposition method. The Pe film on Ag NPs embedded PEDOT:PSS layer shows enhanced optical absorption in the UV–visible region due to the plasmonic absorption by the Ag NPs. At zero bias, the ETL-free Ag NPs-Pe hybrid device shows ∼45% enhanced responsivity and ∼3 times faster photoresponse compared to the pristine device. The enhancements in the performance of hybrid photodetector are attributed to plasmon-enhanced optical absorption and hot electron generation, as well as improvement in charge extraction and transport by Ag NPs, which are corroborated by steady-state and time-resolved photoluminescence measurements. Impedance analysis of the devices shows the reduced carrier transfer resistance of the hybrid device, which results in superior transport of photo-generated charge carriers. Direct evidence for the increase in the work function by ∼47 meV for Ag NPs doped PEDOT:PSS film is provided from the Kelvin probe force microscopy analysis. This increase in work function enables favorable band alignment with reduced energy barrier and a superior carrier transport resulting in improved photodetection performance for the hybrid device. Our results are significant for the development of high-performance, low-cost, ETL free plasmonic perovskite photodetectors for futuristic applications.

Research progress in lead-less or lead-free three-dimensional perovskite absorber materials for solar cells

The trend toward lead-free or lead-less perovskite solar cells (PSCs) has attracted increasing attention over the past few years because the toxicity of lead (Pb) is one of the substantial restrictions for large-scale applications. Researchers have investigated the viability of substituting Pb with other elements (group 14 elements, group 2 elements, transition-metal elements, and group 13 and 15 elements) in the three-dimensional (3D) perovskites by theoretical calculations and experimental explorations. In this paper, recent research progress in Pb-less and Pb-free PSCs on the perovskite compositions, deposition methods, and device structures are summarized and the main problems that hinder the enhancement of device efficiency and stability are discussed in detail. To date, the fully Sn-based PSCs have shown a power conversion efficiency (PCE) of 8.12% and poor device stability. However, lead-less PSCs have shown higher PCE and a better stability. In addition, the introduction of double-perovskite materials also draws researchers’ attention. We believe that the engineering of elemental composition, perovskite deposition methods, and interfacial modification are critical for the future development of Pb-less and Pb-free PSCs.

Precursor effects on methylamine gas-induced CH3NH3PbI3 films for stable carbon-based perovskite solar cells

Carbon-based perovskite solar cells (PSCs) without hole transport material have attracted much attention due to their high stability. However, their power conversion efficiency (PCE) is still low because of the lack of suitable perovskite deposition methods. In this work, a facile solid-gas reaction method was explored to prepare high quality perovskite and the effects of precursor composition (PbI2, PbI2 + HI, HPbI3 and PbI2 + NH4I) on the CH3NH2 (MA) gas-induced perovskite were systematically investigated. The lack of H+/I− and/or HI suppressed the conversion of PbI2 precursor to MAPbI3, while rapid and complete conversion was achieved for (PbI2 + HI), HPbI3 and (PbI2 + NH4I) precursors. Compared with HPbI3 precursor, the presence of H2O molecules in (PbI2 + HI) precursor lowered the perovskite crystallinity, while the release of NH3 from (PbI2 + NH4I) precursor slower the interaction of MA molecules with MAPbI3 for achieving the highest quality MAPbI3 layer. The application of an anti-solvent treatment during precursor deposition further improved the quality of HPbI3 and (PbI2 + NH4I)-processed perovskite layers, which as a result, significantly promoted the photovoltaic performance of C-PSCs. Both devices exhibited considerably high stability, especially for the (PbI2 + NH4I)-processed C-PSCs, who did not show any PCE degradation after storage in air atmosphere at room temperature for 120 days.

Unveiling the Concentration-Dependent Grain Growth of Perovskite Films from One- and Two-Step Deposition Methods: Implications for Photovoltaic Application.

In order to achieve high-efficiency perovskite solar cells, understanding both the crystal structure and the optoelectronic properties of perovskite layers is of importance. This paper uses crystallization analysis and the modeling study of two different perovskite deposition methods (two- and one-step methods) and thereby shows that the one-step method embodies a film formation process that is dominated by crystal growth, while the dominant mechanism of the two-step procedure is nucleation. Our data based on experimental and theory shows that the one-step recipe is superior in terms of morphology control, and, hence, reproducibility, compared to the two-step recipe.

High-quality perovskite in thick scaffold: a core issue for hole transport material-free perovskite solar cells

Organic–inorganic perovskite solar cells (PSCs) have attracted intense attention in the last few years due to the phenomenal increase in power conversion efficiency (PCE), but their low stability has greatly hindered their practical application. By removing unstable hole transport materials (HTM), the device stability of HTM-free PSCs has been greatly improved. However, the PCE has largely lagged behind those of HTM-based PSCs. We contend that deposition of high-quality perovskite into a thick scaffold is the key to achieving high-performance, HTM-free PSCs. Indeed, a few deposition methods have been used to successfully deposit a high-quality perovskite layer into a relatively thick TiO2 scaffold, hence producing PSCs with relatively high PCEs. In this review, we will introduce the basic working principle of HTM-free PSCs and analyze the important role of thick TiO2 scaffold. Most importantly, the problems of the conventional perovskite deposition methods in thick TiO2 scaffold will be examined and some recent successful deposition methods will be surveyed. Finally, we will draw conclusions and highlight some promising research directions for HTM-free PSCs.

Solvent Engineering Boosts the Efficiency of Paintable Carbon‐Based Perovskite Solar Cells to Beyond 14%

Carbon‐based hole transport material (HTM)‐free perovskite solar cells (PSCs) have shown much promise for practical applications because of their high stability and low cost. However, the efficiencies of this kind of PSCs are still relatively low, especially for the simplest paintable carbon‐based PSCs, in comparison with the organic HTM‐based PSCs. This can be imputed to the perovskite deposition methods that are not very suitable for this kind of devices. A solvent engineering strategy based on two‐step sequential method is exploited to prepare a high‐quality perovskite layer for the paintable carbon‐based PSCs in which the solvent for CH3NH3I (MAI) solution at the second step is changed from isopropanol (IPA) to a mixed solvent of IPA/Cyclohexane (CYHEX). This mixed solvent not only accelerates the conversion of PbI2 to CH3NH3PbI3 but also suppresses the Ostwald ripening process resulting in a high‐quality perovskite layer, e.g., pure phase, even surface, and compact capping layer. The paintable carbon‐based PSCs fabricated from IPA/CYHEX solvent exhibits a considerable enhancement in photovoltaic performance and performance reproducibility in comparison with that from pure IPA, especially on fill factor (FF), owing mainly to the better contact of perovskite/carbon interface, lower trap density in perovskite, higher light absorption ability, and faster charge transport of perovskite layer. As a result, the highest power conversion efficiency (PCE) of 14.38% is obtained, which is a record value for carbon‐based HTM‐free PSCs. Furthermore, a PCE of as high as 10% is achieved for the large area device (1 cm2), also the highest of its kind.

Low temperature processing of flexible planar perovskite solar cells with efficiency over 10%

A device fabrication method is reported to efficiently produce CH3NH3PbI3-based planar perovskite solar cells on polymer substrates with the entire process conducted at 150 °C or below. The hole blocking layer employed is a solution processed 100 nm thick mesoporous TiO2 layer. A gas-assisted perovskite deposition method is used to produce excellent coverage of the hole blocking layer by a ∼350 nm thick CH3NH3PbI3 film, resulting in high device performance reproducibility. We show that an average efficiency of 10.6 ± 1.2%, and a maximum efficiency of 12.3% are obtained for flexible perovskite solar cells, offering great promise for further improvement of this low-temperature, low-cost processing solar technology.

Polyfluorene Derivatives are High‐Performance Organic Hole‐Transporting Materials for Inorganic−Organic Hybrid Perovskite Solar Cells

Photovoltaics based on organic−inorganic perovskites offer new promise to address the contemporary energy and environmental issues. These solar cells have so far largely relied on small‐molecule hole transport materials such as spiro‐OMeTAD, which commonly suffer from high cost and low mobility. In principle, polyfluorene copolymers can be an ideal alternative to spiro‐OMeTAD, given their low price, high hole mobility and good processability, but this potential has not been explored. Herein, polyfluorene derived polymers‐TFB and PFB, which contain fluorine and arylamine groups, are demonstrated and can indeed rival or even outperform spiro‐OMeTAD as efficient hole‐conducting materials for perovskite solar cells. In particular, under the one‐step perovskite deposition condition, TFB achieves a 10.92% power conversion efficiency that is considerably higher than that with spiro‐OMeTAD (9.78%), while using the two‐step perovskite deposition method, about 13% efficient solar cells with TFB (12.80%) and spiro‐OMeTAD (13.58%) are delivered. Photo­luminescence reveals the efficient hole extraction and diffusion at the interface between CH3NH3PbI3 and the hole conducting polymer. Impedance spectroscopy uncovers the higher electrical conductivity and lower series resistance than spiro‐OMeTAD, accounting for the significantly higher fill factor, photocurrent and open‐circuit voltage of the TFB‐derived cells than with spiro‐MeOTAD.