Conventional Perovskite Solar Cells Research Articles

Simple Encapsulation Method for Flexible Perovskite Solar Cells with Transparent Electrode‐Integrated Barrier Films

Flexible perovskite solar cells (PSCs) have been rapidly developed for realistic applications such as windows and auxiliary power supplies of other electronics. However, the penetration of moisture through the cell’s flexible substrate films still poses a major obstacle because it can destroy the perovskite active films under outdoor conditions. Unlike conventional PSCs with glass‐based encapsulation, flexible PSCs face challenges in finding suitable materials and structures that maintain flexibility while providing effective encapsulation. We propose simple encapsulation methods suitable for flexible PSCs using a transparent electrode‐integrated flexible barrier (TIFB) substrate comprising silicon nitride (SiNx)/polyethylene terephthalate (PET)/indium tin oxide (ITO). We deposit a dense SiNx layer with CVD on ITO‐PET films and achieve a more flexible TIFB than the conventional laminated substrate owing to its thinness. TIFB shows a low water vapor transmission rate (WVTR) of 4.3×10‐3 g/m2·day. Consequently, the efficiency of TIFB‐based PSCs under harsh conditions (60 °C and 90 RH%) exhibits an acceptable decrease within 10% of its highest efficiency after 400 h storage, which is the most stable data under high temperature and humidity among existing flexible encapsulated PSCs. TIFB, as a flexible substrate, is a major candidate to protect flexible electronics and PSCs against external factors.This article is protected by copyright. All rights reserved.

Effect of PEDOT:PSS optical properties at the frontal interface on electrical performance in MAPbI3 perovskite solar cells

This article presents a thorough analysis of perovskite-based solar cells (PSCs) by integrating optical and electrical simulations. The investigation includes simulations of both optical and electrical characteristics of a PSC configuration featuring a MAPbI3 active layer, PEDOT:PSS as the hole transport layer (HTL) at the front interface, and PC60BM and BCP at the back interface. Optical simulations utilized the optical admittance method and transfer matrix method, with optical constants such as refractive index (n) and extinction coefficient (k) derived from transmittance measurements of the fabricated layers. Electrical simulations were performed using the Solar Cell Capacitance Simulator One Dimension (SCAPS-1D) software, focusing on the influence of optical losses due to total reflection at the interfaces. Discrepancies in short-circuit current density (Jsc) of about 3 mA/cm2 were revealed between simulations employing optical constants of PEDOT:PSS determined via Tauc-Lorentz-Drude (TLD) and B-spline (BSPL) model fitting to transmittance data. Optimal parameters for achieving the highest power conversion efficiency (PCE) were identified, with PEDOT:PSS layer thicknesses below 15 nm and MAPbI3 layer thicknesses above 305 nm. The maximum efficiency ranged between 10.42 % and 12.10 %, close to conventional experimental perovskite solar cells with the same structure. A key observation highlighted the overestimation of Jsc and PCE when simulated total reflectance was neglected in electrical simulations. These findings underscore the significance of incorporating optical data into electrical simulations, offering critical insights for PSC optimization. Overall, this study enhances our understanding of the intricate relationship between optical and electrical parameters, essential for advancing high-performance PSC development.

Enhancing Interface Interaction through Multifunctional Trisodium Citrate Modification of Electron‐Transport Layer in Fully Air‐Processed Perovskite Solar Cells

Electron‐transport layer (ETL) is integral in conventional perovskite solar cells (PSCs), serving as an essential role in both the growth of perovskite and the extraction of charge carriers. This dual functionality poses a challenge, especially in the context of the ETL in all‐air‐processed PSCs. Herein, a multifunctional modification strategy is proposed, where trisodium citrate (TC) is incorporated into SnO2 precursor. The introduction of TC can efficiently inhibit the agglomeration of SnO2 nanoparticle in precursor. This also eliminates the oxygen vacancy defects and reduces the work function of the SnO2 film surface. This synergistic effect remarkably improves the quality of ETL. Meanwhile, TC can passivate the undercoordinated Pb2+ at the buried interface, thus suppressing nonradiative recombination and reducing lead leakage. Furthermore, Na ions in the TC molecule facilitate the perovskite crystallization by migrating into the perovskite layer, resulting in formation of a high‐quality perovskite film. Consequently, the efficiency of the TC‐treated device made in fully ambient‐air conditions reaches 21.17% with suppressing hysteresis. In particular, the unencapsulated device maintains about 81% of the original efficiency after 2500 h under air exposure. In this study, a straightforward and effective method is presented for achieving efficient and stable air‐processed PSCs.

A review on conventional perovskite solar cells with organic dopant-free hole-transport materials: roles of chemical structures and interfacial materials in efficient devices

Efficient conventional perovskite solar cells with organic dopant-free HTMs are collected. It is showed that both the chemical structure of HTMs and interfacial materials play significant roles in efficiency, and their effects are discussed.

Chalcogenide Perovskite, An Emerging Photovoltaic Material: Current Status and Future Perspectives

AbstractChalcogenide perovskite materials came into the picture of photovoltaic technology since 2015. Their admirable structural, electronic and optical properties make them highly promising for solar energy conversion. They have immense potential to solve the stability and toxicity issues of conventional perovskite solar cells. The maximum theoretical power conversion efficiency reported for them is about 30 % which is similar to CH3NH3PbI3 perovskite material. However their application in photovoltaics is limited by several challenges. In this review, we tried to provide an overview of the structural features of the chalcogenide perovskite materials and critically highlighted computational and synthetic accomplishments in this area. Various techniques developed for synthesizing these materials so far, have also been summarized. Along with that, the challenges associated in designing these materials for improved optoelectronic properties are also addressed. Serious research efforts are urgently needed for the realization of the dream of chalcogenide perovskite material based solar cells in terms of optimization of optoelectronic properties, synthetic cost, processing of thin films and application in tandem solar cell devices. This review may facilitate further progress in chalcogenide perovskite material based thin film solar cell in the future.

Exploring the Potential of MXene Contacts on Wide‐Bandgap Dion–Jacobson Perovskite Solar Cell: A Numerical Study

The stability and performance challenges in conventional 3D perovskite solar cells (PSCs), attributed to perovskite structure and transport layers, prompt the exploration of 2D perovskites. However, the presence of transport layers and conventional contacts is still challenging as it creates interface defects and pinholes. In this study, a new transport‐layer‐free device structure, i.e., MXene–2D perovskites–MXene‐based metal–semiconductor–metal PSCs, is introduced to resolve the stability‐ and performance‐related issues. The proposed solar cell incorporates PeDAMAPb2I7 as the absorber layer and MXenes (Hf2NF2/Ta4C3F2) as electrodes. The Dion–Jacobson perovskites solar cell is also investigated for optimum thickness and defect tolerance level of PeDAMAPb2I7. In the results, it is indicated that the device delivered the maximum efficiency of 5.63% at a 500 nm thick absorber layer with a defect density of 1 × 1013 cm−3. Further, the quest to find suitable MXene contact for electron extraction is met by analyzing the proposed solar cell with nine different MXene layers (Hf2NF2, Hf2CF2, Zr2NF2, Ta2CF2, Ti4C3, Ti3C2, Zr2C, Sc2C, Ti2C). In the results, it is indicated that Hf2NF2 has a 3.2 eV work function, making it the optimal choice, achieving 5.63% efficiency.

A conductive adhesive ink for carbon-laminated perovskite solar cells with enhanced stability and high efficiency

Utilizing carbon-laminated electrodes on perovskite solar cells (PSCs) benefits from simple fabrication process and low-cost material, in addition to enhanced stability. In this method, carbon foils are laminated on the underlying hole transport layer (HTL), so the HTL/carbon electrode interface is of the utmost importance in achieving high-performance devices. Here, we develop a conductive adhesive ink, consisting of poly methyl methacrylate (PMMA), highly conductive carbon black (HCCB), and CuInS2 (CIS) nanoparticles, as the interfacial adhesive layer between the underlying CIS HTL and the top carbon electrode. Utilizing carbon foil, wetted by the proposed optimized adhesive ink layer, allows simply pressing the top carbon electrode on CIS HTL. The prepared optimized carbon-laminated PSCs lead to a maximum power conversion efficiency (PCE) of 17.2 % for the best PSC, as compared with the maximum PCE of 18.2 % for the best sample of conventional Au-based PSC. Furthermore, the average PCE of the fabricated optimized carbon-laminated PSCs has kept almost 92 % of the average maximum PCE value after about 54 days, which is a significant enhancement in device stability in comparison with conventional Au-based PSCs, which have degraded to 75 % of their maximum PCE. The proposed carbon lamination method seems very promising for overcoming the stability challenge of PSCs, and the realization of low-cost, large-area, highly stable, and efficient solar cells.

Preparation of NaYF4:Tm, Yb, and Gd Luminescent Nanorods/SiO2 Nanospheres Composite Thin Film and Its Application in Perovskite Solar Cells.

In this study, we aim to minimize light loss and achieve high power conversion efficiencies (PCE) in perovskite solar cells (PSCs) by employing a spectral conversion film component with antireflection properties. In our scheme, NaYF4:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films are applied on CH3NH3PbI3 PSCs to improve the device efficiency. The film was fabricated by spin coating an aged silica sol containing NaYF4:Tm, Yb, and Gd luminescent nanorods. The size and the spectral conversion properties of the NaYF4:Tm, Yb, and Gd luminescent nanorods were controlled by tuning the Gd3+ ion concentration. The microstructure and the transmittance properties of the thin film were controlled by changing the concentration of NaYF4:Tm, Yb, and Gd luminescent nanorod in silica sol. The thin films have excellent spectral conversion properties while exhibiting a maximum transmittance. The photovoltaic performance of PSCs with NaYF4:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films was systematically investigated. The light transmittance was optimized to 95.1% on a cleaned glass substrate, which resulted in an average increase of about 3.0% across the broadband range of 400-800 nm. The optimized films widen the spectrum of light absorbed by conventional PSC cells and reduce reflections across a broad range, enhancing the photovoltaic performance of PSCs. As a result, the PCE of the PSC increased from 14.51% for the reference device without a thin film to 15.67% for the PSC device with an optimized thin film. This study presents a comprehensive solution to the problem of Fresnel reflection and spectral response mismatch of the PSCs, which provides new ideas for the light management of PSCs.

Potassium chloride passivation for sputtered SnO2 to eliminate hysteresis and enhance the efficiency of perovskite solar cells

In perovskite solar cells (PSCs), tin oxide (SnO2) has been widely used as the electron transport layer (ETL) due to its wide bandgap and high electron mobility. Among the various deposition methods, radio frequency (RF) sputtering offers many advantages for the commercialization of PSCs fabrication. However, conventional PSCs with sputtered SnO2 are subject to severe hysteresis, which occurs owing to defect sites at the ETL-perovskite interface. Further, these defect sites induce non-radiative carrier recombination, causing a decrease in open-circuit voltage and device fill factor. Herein, the surface of RF-sputtered SnO2 was passivated with potassium chloride (KCl) aqueous solution. Through this treatment, it was possible to passivate the defect sites at the interface and change the band alignment for effective electron transport. Thus, a decrease in the trap density of the perovskite led to an increase in efficiency (from 20.9% to 21.9%) and reduction in the hysteresis (from 10.5% to 2.7%) of the PSC. Hence, the KCl passivation process of RF-sputtered SnO2 could be adopted to manufacture hysteresis-free high-efficiency PSCs.

Performance optimisation of n-i-p type CH3NH3PbI3 based perovskite solar cells using SCAPS 1-D device simulation

Perovskite solar cells (PSCs) are emerging photovoltaic technologies with an efficiency of over 25%. PEDOT:PSS is the most commonly used hole transport material in the p-i-n type perovskite solar cell because the PEDOT:PSS dispersion is typically water-based material. Water-free PEDOT:PSS composites are used in the n-i-p architecture. The inverted PEDOT:PSS-based PSCs show 200 mV less open circuit voltage (VOC) as compared to conventional PSCs. Herein, the n-i-p type perovskite solar cell containing PEDOT:PSS as a hole transport layer is adopted to overcome the problem of open circuit voltage loss in an inverted solar cell. The design and analysis of n-i-p based perovskite solar cell is carried out using the 1D-Solar Cell Capacitance Simulator. The solar cell performance is improved by optimising the different parameters of perovskite solar cell. The optimised n-i-p structure solar cell has achieved the best power conversion efficiency of over 18% with 1.27 V open-circuit voltage for 350 nm thickness of the absorber layer. Therefore, the results provide a pathway to overcoming the voltage loss in PEDOT:PSS-based inverted PSCs by adopting a conventional device structure.

Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells

Hole transport material-free carbon-based perovskite solar cells (HTM-free C–PSCs) are recognized as a cost-effective and stable alternative to conventional perovskite solar cells. However, the significant energy level misalignment between the perovskite layer and the carbon counter electrode (CE) results in ineffective hole extraction and unfavorable charge recombination, which decreases the power conversion efficiency (PCE). Here, we report the introduction of metal salts (Al, Ca, and Mg) into graphite/carbon black (Gr/CB) CEs to modify the work function and enhance the hole selectivity of the CE. This modification leads to improved energy level alignment, efficient hole extraction, and reduced charge recombination. The PCE of the HTM-free C-PSC based on Al-modified Gr/CB as the CE material reached 9.91%, which is approximately 12% higher than that of devices employing unmodified Gr/CB CEs. This work demonstrates that by directly incorporating metal salts into the Gr/CB CE, the energy level alignment and hole extraction at the perovskite/carbon interface can be improved. This presents a viable method for enhancing the PCE of HTM-free C–PSCs.

Understanding the Interfacial Reactions and Band Alignment for Efficient and Stable Perovskite Solar Cells Built on Metal Substrates with Reduced Upscaling Losses.

Conventional perovskite solar cells (PSC) built on transparent conductive oxide (TCO) glass face a fundamental challenge to retain fill factor (FF) for large-area upscaling due to series resistance loss. Building a perovskite solar cell on metal has the potential to reduce this FF loss and is promising for flexible applications. However, their efficiency and stability lag far behind their TCO counterparts. Herein, findings on the complex chemical reactions and degradation-promoting processes at different perovskite/metal (Cu, Au, Ag, and Mo) interfaces, which are closely linked with the inherent stability; and the interlayer engineering for perovskite/metal interface's band alignment, which plays an essential role in achieving high efficiency, are reported. Leveraging these findings, 21% power conversion efficiency (PCE) is achieved for 1 cm2 perovskite solar cells using a p-i-n top-illumination structure on a molybdenum substrate, the highest reported for a PSC built on metal. Notably, the FF and PCE losses due to area upscaling are remarkably reduced by one order of magnitude relative to the counterparts on conventional TCO glass, highlighting an alternative pathway for PSC upscaling and module design.

A modified architecture of a perovskite solar cell with an enhanced optical absorption in the visible spectrum

The incomplete absorption of light in the perovskite solar cells (PSCs) due to the escape of photons and the waste of their energy in the visible spectrum hinders the efficiency of this type of solar cell. Utilizing light-trapping nanostructures and stimulating the device’s plasmonic is an efficient way to increase absorption and reduce the energy losses. In this paper, a novel configuration of a nanostructured PSC with a plasmonic enhancement has been introduced to confine light in the active layer and boost energy harvesting. According to the conducted calculations, the modified configuration supports 23.4% higher short-circuit current density (J SC) and 21% power conversion efficiency compared to the conventional PSC. In this study, the finite element method has been employed to perform numerical simulations of the examined structures. For modeling and characterizing solar cells, optical physics of the devices is used in conjunction with their electrical physics.

Systematic investigation of the impact of kesterite and zinc based charge transport layers on the device performance and optoelectronic properties of ecofriendly tin (Sn) based perovskite solar cells

Methylammonium tin triiodide (MASnI3) perovskite solar cells (PSC) have gained a lot of interest due to their edge over conventional Pb-based PSC in terms of less-toxic nature, wider optical absorption range and smaller bandgap. In this work, 24 novel n-i-p heterostructures of MASnI3 PSC have been analyzed in detail with various zinc-based electron transport layers (ETL) and kesterite-based hole transport layers (HTL). The proposed device architecture (FTO/ETL/CH3NH3SnI3/HTL/Back contact) performance was first enhanced by optimizing the thickness and then by the doping concentration of each layer via SCAPS-1D simulator under AM 1.5G illumination. The energy band alignment of the different charge transport layers (CTL) with MASnI3 was analyzed in detail to understand its working principle. Moreover, the effects of optical absorption, band offsets, electric field, defect density, interface defects, temperature, rear reflective coating, and electrodes are monitored to characterize the performance of each cell structure. Among all the proposed structures, ZnO/MASnI3/CNTS based perovskite solar cell performed outstandingly well with Jsc of 29.44 mA cm−2, Voc of 1.12 V, FF of 88.82 %, and PCE of 29.24 %. These simulations provided important insights into the mechanism of carrier transport and the factors affecting the performance of solar cells. The results in this paper will help the research community in fabricating highly efficient eco-friendly solar cells.

Self-healing perovskite solar cells based on copolymer-templated TiO2 electron transport layer

Inorganic hole-transport materials (HTMs) such as copper indium disulfide (CIS) have been applied in perovskite solar cells (PSCs) to improve the poor stability of the conventional Spiro-based PSCs. However, CIS-PSCs' main drawback is their lower efficiency than Spiro-PSCs. In this work, copolymer-templated TiO2 (CT-TiO2) structures have been used as an electron transfer layer (ETL) to improve the photocurrent density and efficiency of CIS-PSCs. Compared to the conventional random porous TiO2 ETLs, copolymer-templated TiO2 ETLs with a lower refractive index improve the transmittance of input light into the cell and therefore enhance the photovoltaic performance. Interestingly, a large number of surface hydroxyl groups on the CT-TiO2 induce a self-healing effect in perovskite. Thus, they provide superior stability in CIS-PSC. The fabricated CIS-PSC presents a conversion efficiency of 11.08% (Jsc = 23.35 mA/cm2, Voc = 0.995, and FF = 0.477) with a device area of 0.09 cm2 under 100 mW/cm2. Moreover, these unsealed CIS-PSCs retained 100% of their performance after aging tests for 90 days under ambient conditions and even increased from 11.08 to 11.27 over time due to self-healing properties.

Two Birds with One Stone: Dual‐Functional Difluorinated Modifier Enabling Efficient and Stable Perovskite Solar Cells

The interface between the perovskite layer and charge transport layer (CTL) plays an important role in the photoelectric conversion of perovskite solar cells (PSCs). In essence, the presence of defects and unideal contact at the perovskite/CTL interface induces severe nonradiative charge recombination, thus limiting the open‐circuit voltage and fill factor of PSCs. Herein, a two‐birds‐with‐one‐stone strategy to overcome the earlier challenges is reported, in which a single reagent 3,5‐difluorobenzenesulfonamide (3,5‐DFBS) is applied as an interface modifier between perovskite layer and spiro‐OMeTAD hole transport layer (HTL) in conventional PSCs. The 3,5‐DFBS molecules can passivate the undercoordinated Pb2+‐related surface defects by forming coordination through SO group and simultaneously strengthen the perovskite/HTL interface contact via F–π interactions, thus promoting hole extraction greatly. As a result, a champion efficiency of 23.69% with substantially improved stability is accomplished for 3,5‐DFBS PSCs. This work demonstrates that the two‐birds‐with‐one‐stone strategy is promising for achieving highly efficient and stable PSCs.

Spring‐Like Ammonium Salt Assisting Stress Release for Low‐Temperature Deposited FAPbI3 Films Toward Flexible Photovoltaic Application

AbstractThe substrates of conventional flexible perovskite solar cells (FPSCs) are thermoplastic polymer material polyethylene naphthalate (PEN), which will deform during high temperature annealing process. In addition, lead iodide (PbI2) permanently formed and the substrate undergoes reversible deformation from 20 °C to 200 °C and back to 20 °C. Therefore, to balance the substrate supporting capacity and the crystalline quality of narrow band gap α‐phase formamidinium lead iodide (α‐FAPbI3), an annealing process of 120 °C for 30 minutes is determined. Additionally, there will also be a large number of gaps and lattice strain at the perovskite grain boundaries during the annealing process as the FAPbI3 phase transition is accompanied by much lattice shrinkage. As a result, 1,6‐hexanediammonium diiodide (HADI) is chosen to passivate the defects and release the stress of perovskite film. Therefore, a recorded 1.4% extended stretch rate of the flexible film is attained. Finally, the champion PCE of 21.14% under AM 1.5G and 31.52% under 1062 lux is achieved after HADI treatment, accompanied by a better long‐term and mechanical stability. This study provides annealing process optimization and stress relief strategies for the further development of narrow band gap FPSCs.

Small molecule dopant-free dual hole transporting material for conventional and inverted perovskite solar cells

Small molecule dopant-free HTL with the ability to self-assemble shows a dual performance that leads to very similar efficiencies in p–i–n and n–i–p perovskite solar cells.

Prospect of near-infrared quantum dots in the development of tandem solar cells: Detail charge balance study

The conventional single-junction solar cells (ex: monocrystalline silicon (cSi) and perovskite solar cells) are limited to 30% efficiency, known as the Shockley–Queisser limit. Due to operational constraints, the single-junction solar cells are transparent to a large part of the near-infrared (NIR) solar spectrum. Harvesting the unused NIR photons in tandem solar cells could be a potential way forward. However, the unavailability of suitable NIR bandgap semiconductors is a huge practical challenge in realising tandem solar cells. The advancement of nanotechnology has enabled size dependent tunability of energy bandgap of semiconductors quantum dots (QDs). It is shown here that NIR bandgap QDs can be used to augment the performance of the existing perovskite and cSi solar cells in tandem architecture. Using detailed charge balance calculation, the optimum bandgaps of QDs for the development of perovskite-QD and cSi-QD tandem solar cells have been identified. Further, It is also depicted that the QD solar cells can produce 11.8% and 5.2% efficiency by using the unused transmitted photons which improve the limiting efficiency from perovskite and cSi solar cells, respectively. In tandem solar cells, this may help realise 39.8% and 34.2% efficiency in the case of perovskite-QD and cSi-QD tandem solar cells.

Simultaneously Modifying Hole Transport Material and Perovskite via a Crown Ether‐Based Semiconductor Toward Efficient and Stable Perovskite Solar Cells

In conventional (n‐i‐p) perovskite solar cells (PSCs), spiro‐OMeTAD is the most widely used hole‐transporting material (HTM), which contributes to the current state‐of‐the‐art efficiency. Suffering from the low conductivity, dopants such as LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and tBP are usually required to achieve excellent hole transport properties in spiro‐OMeTAD. Nevertheless, the hygroscopicity and the migration of Li+ during device operation severely affect the device's stability. To address the aforementioned issue, a 12‐crown‐4‐based organic semiconductor (CDT) is synthesized and applied in PSCs. Notably, CDT is simultaneously doped in spiro‐OMeTAD and perovskite layer through the antisolvent method. In this way, the strong “host‐guest” interaction between crown ether and Li+ effectively inhibits its migration both in the hole transporting layer (HTL) and at the perovskite/HTM interface. Furthermore, the carbazole diphenylamine group in CDT facilitates hole transport, and meanwhile improves the hydrophobicity of the HTL. In addition, CDT added into the perovskite layer is also able to passivate defects by interacting with the undercoordinated Pb2+. In light of the aforementioned advantages, the CDT‐based device shows a high power conversion efficiency approaching 23%, with excellent long‐term stability.