Traditional Perovskite Solar Cells Research Articles

Inorganic Pb-Sn Perovskite Solar Cells with CF3-PA Internal Defect Passivation Strategy

Abstract The volatile organic components and heavy metal components in traditional perovskite solar cells (PSCs) have raised environmental and stability concerns for their large scale application. To solve the above two problems, the advancement of inorganic Pb-Sn PSCs technology has progressed at a remarkable pace over a relatively short period. Replacing Pb with Sn in PSCs not only significantly improves the environmental problems caused by the high toxicity of Pb, but also forms solar cells with lower bandgap, which is beneficial for light absorption and utilization, especially in the near-infrared band. In this work, a composite inorganic perovskite was utilized, CsPb0.6Sn0.4I3, and enhanced the PSCs performance by passivating the perovskite using 4-trifluoromethyl-phenylammonium (CF3-PA) additives. The highest efficiency of the champion device reached 13.04%, demonstrating its potential as a candidate for low bandgap PSCs.

Bimetallic MOFs derivative LaFeO3@C for efficient and stable carbon-based perovskite solar cells

Carbon-based MAPbI3 perovskite solar cells (C-PSCs) have attracted significant attention due to their low cost and stable performance. However, due to inherent structural defects and an energy level mismatch between the perovskite layer and the carbon electrode, C-PSCs still show a poorer power conversion efficiency (PCE) than traditional perovskite solar cells (PSCs). In this study, LaFeO3@C nanocomposite particles were successfully synthesized via pyrolysis of La-containing MIL-100(Fe) MOF gel. By introducing these pre-synthesized LaFeO3@C bimetallic composite oxide nanoparticles into the carbon electrode, the device featuring a FTO/SnO2/CH3NH3PbI3/LaFeO3@C/C architecture achieved an impressive maximum PCE of 16.35%, surpassing that of the pristine device by 9.36%. The enhanced optoelectronic performance can be primarily attributed to enhanced interfacial contacts, superior interfacial charge extraction ability, and better electrical conductivity. The LaFeO3@C-based device maintained more than 90% of the initial PCE after being stored for 31 days at room temperature and ambient humidity. This study provides a novel strategy for the preparation of efficient and stable C-PSCs from the perspective of spatial structure regulation of bimetallic MOF-based composites.

Performance Analysis of Triple‐Cation Mixed‐Halide Bifacial Perovskite Solar Cell with 17% Rear and 25% Front Efficiency

The goal of bifacial technology is to increase the efficiency of solar cells (SC) by capturing albedo sunlight and converting it to electrical energy. The use of triple‐cation mixed‐halide perovskite solar cells (PSC) has sparked a lot of curiosity and could be the potential for improved power conversion efficiency (PCE) associated with traditional PSCs. Herein, n–i–p‐configured triple‐cation mixed‐halide‐based bifacial PSC is studied using the SC capacitance simulator 1D tool. Through our simulation, the impact of thickness in electron and hole transport layers (ETL and HTLs), defect density, doping density, and the thickness of the light‐harvesting layer on the device performance is examined. With an optimal design, the device exhibits an absolutely staggering efficiency of 25.28% from the front side and around 17.19% from the rear. This cell, due to its high albedo absorption, linearly enhances the short‐circuit current; hence, it overcomes the classical current‐matching limit of ordinary PSCs. The proposed device FTO/TiO2/[Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3]/CuSbS2 has a remarkable efficiency that increases linearly with albedo, making it very appealing for new, high‐efficiency solar applications.

Simulated bending test analysis of 23% efficient lead-free flexible perovskite solar cell with different bending states

Perovskite solar cells (PSCs) have emerged as a promising technology for developing highly efficient and low-cost photovoltaic (PV) devices. However, toxicity is the primary limiting factor that is restraining the use of traditional PSCs. Therefore, lead-free PSCs have been considered the best alternative due to lead toxicity and environmental impact. The secondary obstacle hindering the potential of PSCs for wearable applications is their limited flexibility. Therefore, lead-free flexible PSC (F-PSC) device is designed and simulated through the Silvaco-TCAD tool in this work. Despite the significant advancements made in F-PSCs, insufficient research is conducted to examine their performance under different bending states to study the reliability of the device’s flexibility. Here, three different bending states have been reported to investigate the proposed device performance, viz. convex, concave, and sinusoidal. The impact of bending radius (BR) in convex and concave from 5 to 20 mm and bending amplitude (BA) in the sinusoidal state from 0.5 to 2 mm is studied and analyzed to optimize the device performance. The performance of the proposed lead-free F-PSC is explored in terms of the current density (JV) curve, PV parameters, and external quantum efficiency (EQE). Optimized PV parameters of the proposed F-PSC are: short-circuit current density (JSC) of 33.45 mA cm−2, open-circuit voltage (VOC) of 0.925 V, fill factor (FF) of 77.15% and PCE of 23.87%. The findings of the reported study would significantly provide a path for the development of F-PSC.

Morphology evolution of ultra-stable and low-cost all-inorganic lead-free perovskite solar cells

The emergence of all-inorganic lead-based perovskite solar cells (PSCs) has generated enormous interest in the perovskite research community. The presence of lead (Pb) in these devices, however, has caused some challenges because of its high toxicity, which slows down or even hinders their commercialization. Here we report the successful fabrication of all-inorganic Pb-free PSCs with environment-friendliness, low cost, and excellent stability. In such devices, novel Cs3Sb2I9 perovskite films were prepared by a solution-based method, which possess high-quality morphology, long carrier lifetime, low defect density, and a well-matched band structure with other functional layers. Additionally, carbon electrodes were introduced to replace the labile organic components and expensive noble metal electrodes commonly seen in the traditional PSCs. As a result, the all-inorganic Pb-free PSCs exhibit a champion PCE of 1.43%, which is more than two times higher than the results from previous reports. More importantly, the all-inorganic Pb-free PSCs demonstrated excellent stability under various extreme conditions, such as constant illumination, high humidity, and high temperature. This study provides very useful insights into the development of next-generation commercial PSCs with environment-friendliness, low cost, and excellent stability.

Improving the performance of organic lead–tin laminated perovskite solar cells from the perspective of device simulation

The toxic lead in traditional perovskite solar cells (PSCs) poses a fatal threat to the environment, and it takes time and technology to complete the transition to lead-free perovskite solar cells. In this work, we introduce a lead–tin laminated perovskite solar cell, which can obviously reduce the toxicity of lead. Our ultimate goal is to study the factors that affect the performance of the device. On the basis of reducing the lead-based perovskite layer, use SACPS-1D (solar cell capacitor simulator) to optimize the parameters to maximize the performance of the entire device. Adjusting the physical parameters, we got the power conversion efficiency (PCE) of 17.59% and 6.14% for single-cell lead-based and single-cell tin-based perovskite solar cells respectively, which are close to the experimental results. The simulation results show that under the laminated structure, the thickness of the two perovskite absorber materials based on lead and tin has a certain influence on the performance of the device. After optimization, it is determined that the best thicknesses of lead-based absorption layer (LBA) and tin-based absorption layer (TBA) are 20 nm and 150 nm respectively. Optimize the doping concentration of acceptor and donor of the laminated perovskite absorber layer to obtain higher PCE and open circuit voltage (VOC). The best values are 1015 cm−3 and 1016 cm−3 for LBA and TBA respectively. We also found that when adjusting the positions of LBA and TBA, the recombination rate under different defect densities verified that the laminated absorption layer close to the light source side dominates the device performance. Provide reference for future optimization of laminated perovskite solar cells. Considering these factors comprehensively, we optimized the device performance parameters as follows: VOC = 0.93 V, JSC = 19.56 mA/cm2, FF = 71.12% and PCE = 12.89%.

Design and simulation of efficient tin based perovskite solar cells through optimization of selective layers: Theoretical insights

Within a decade, Perovskite solar cells (PSCs) have attained an efficiency of 25.8%. PSCs lack commercialization due to two main factors: (i) poor device stability (ii) toxicity. The tin (Sn) is a possible candidate to substitute toxic lead (Pb) in traditional PSCs; however, the performance of Sn-based PSCs is 13%, much lower than Pb-based PSCs due to several aspects. In this work, we have used drift-diffusion simulation to propose a pathway to improve the performance of lead-free PSCs using MASnI3 as a light harvester. The conventional charge selective layer, such as TiO2, requires high-temperature processing, which also is a major concern. As reported earlier, traditional transport layers contribute actively to the degradation of PSCs, affecting their stability. Therefore, we have used ZnO nanoparticles (NP) as electron transport material (ETM), and conducted an analysis using various organic and inorganic hole transport materials (HTMs) with spike and cliff structures. The impact of HTM thickness on the performance parameters of MASnI3 based PSCs with constant and variable charge acceptor concentrations was investigated. This work indicates that organic HTMs exhibit more thickness-dependent behavior than inorganic HTM for MASnI3 based PSCs. Furthermore, the suitable valence band offset (VBO) and barrier height at Perovskite/HTM and HTM/Back contact interfaces were studied for efficient energy level mismatch with absorber layer to boost the performance of MASnI3 based PSCs. The concept of selecting back contact for Sn-based PSCs using different HTMs was analyzed. The influence of temperature variation on the performance of PSCs using different HTM was analyzed. The hybrid configuration devices face the issue of interfacial recombination; thus, the impact of defect density at the HTM/MASnI3 interface on the performance of PSCs with various HTMs was investigated. Lastly, MASnI3 based PSC showed a power conversion efficiency (PCE) of 23.51% using the unmodified CuSCN based HTM and, CuI can also deliver an efficiency of 23.31% employed modified valence band energy level.

Morphology controlled (CH3NH3)3Bi2Cl9 thin film for lead free perovskite solar cell

Traditional perovskite solar cells have made tremendous progress in terms of efficiency in the past few years but the presence of toxic lead (Pb) has restricted their commercialization. We report here a process to fabricate MABiCl perovskite thin film based solar cell. The process shows some intriguing outcomes like uniform surface morphology of the perovskite layer, high open-circuit voltage and good fill-factor. The film shows improved uniform morphology and surface coverage with flakes (dimensioñ 570 nm × 360 nm, thickness ∼ 100–200 nm. The solar cell device shows an open-circuit voltage of about 496 mV and a fill factor 0.55. The improved morphology of the perovskite layer with reduced number of defects and charge traps possibly decreases the probability of recombination of photoexcited charge carriers. The result indicates that the process can be a good alternative to prepare lead free perovskite solar cells with improved performance.

Efficient and Stable Perovskite Solar Cells with a Superhydrophobic Two-Dimensional Capping Layer.

A two-dimensional (2D) perovskite layer is considered to be a desirable defect passivation structure for the lifelong stability of perovskite solar cells (PSCs). However, the efficiency could be compromised behind the traditional PSCs. Herein, we solve this issue by employing a highly hydrophobic organic cation, 2-[4-(trifluoromethyl)phenyl]ethanamine (CF3-PEA), to form a 2D (CF3-PEA)2PbI4 to effectively passivate the 3D MAPbI3 with fewer defects. The new 2D/3D-structured PSCs show reduced charge recombination, an elongated carrier lifetime, efficient charge generation and transport. Those excellent characters lead to a significant enhancement of the efficiency from 17.9% for pristine PSCs to 21.43% for 2D/3D PSCs. Benefiting from the high hydrophobicity of CF3-PEA, the cells show remarkably improved stability by maintaining 83% of the original efficiency exposed to 80% R.H. and 50 °C for 600 h and 87% under 1 sun illumination for 600 h, which makes our PCSs among the most efficient and stable MAPbI3 solar cells.

Advances on tin-based perovskite solar cells

<p indent=0mm>Organic–inorganic hybrid perovskites have been a focus in the photovoltaic research field due to their remarkable advantages such as tunable direct bandgap, low exciton binding energy, high light harvesting, and so on. The power conversion efficiency (PCE) of lead (Pb)-based perovskite solar cells (PSCs) has been rapidly raised from 3.8% to 25.5% over the decades. With the advantages of a simple preparation process and low production cost, PSCs have great potential in commercialization. However, the toxicity of lead in traditional PSCs limits their large-scale production. Among all lead-free perovskites, the tin-based one inherits the majority of the excellent photoelectric properties of lead-based perovskites. However, the maximum PCE of tin-based PSCs has only exceeded 13%. Although the electronic structure of Sn²⁺ is similar to that of Pb²⁺, it is easy to be oxidized to Sn⁴⁺, and the formation energy of Sn vacancy defects is low, resulting in heavy p-doping in tin-based perovskite films. The background carrier concentrations of tin-based perovskites are as high as <sc>10¹⁸–10²⁰ cm^–3,</sc> which makes photo-generated carriers easy to be recombined. Tin-based perovskites usually experience single-molecule recombination, accompanied by a small amount of bi-molecular recombination, and Auger recombination is negligible. Therefore, reducing recombination in tin-based perovskites is to suppress the single-molecule recombination. At present, additive engineering and component modification strategies are mainly adopted to inhibit carrier recombination in tin-based PSCs. Additive engineering includes tin compensating additives, reducing additives and some other additives which interact with perovskites. Theories and experiments show that adding tin compensating additives in precursor solution can effectively improve the chemical potential of Sn and increase the formation energy of tin vacancies. Although the work mechanism of stannous halide as an additive is not fully understood, it has become an indispensable part to prepare high performance tin-based PSCs. The introduction of reducing additives in the precursor can effectively reduce Sn⁴⁺ and inhibit the oxidation of Sn²⁺, thereby inhibiting the generation of tin vacancies, optimizing the morphology of the film, and improving the efficiency and stability of the device. In addition, some additives which interact with perovskite through coordination bonds, ionic bonds and hydrogen bonds can optimize the nucleation rate of tin-based perovskites and passivate the unsaturated coordination of Sn²⁺ at the grain boundaries. The composition modification of tin-based perovskites mainly includes A-site and X-site substitutions. Since the band structure of tin-based perovskites is mainly determined by Sn and X ions, A-site cation substitution only fine-tunes the bandgap of the perovskite. However, A-site cation substitution can tune the tolerance factor of perovskite, thereby improving the efficiency and stability of perovskite. As the alkyl chain of the A-site cation gradually increases, low-dimensional perovskites will be formed. The low-dimensional perovskite can inhibit the self-doping and ion migration, improve the efficiency and stability of the PSCs. It is worth noting that the current efficient tin-based PSCs are mainly focused on low-dimensional perovskites. In addition, since the np² electrons of halogens directly participate in the construction of the electronic structure, the bandgap of tin-based perovskites can be directly changed by adjusting the X-site anions. Compared with lead-based perovskites, tin-based ones have more suitable bandgap and higher theoretical efficiency. At the same time, the low toxicity of tin-based perovskites is also conducive to their large-scale industrial production. It is believed that with the in-depth research, tin-based perovskite will surely exert its full potential in the photovoltaic field.

Photo-response of Two-Dimensional Ruddlesden-Popper Perovskite Films for Photovoltaics

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites have emerged as a prospective candidate to address the instability issues of traditional perovskite solar cells. However, the mechanisms of charge carrier transport of 2D perovskite films obtained by the solution process still remain elusive. In this work, we proposed a novel characterization technique based on the Kelvin probe force microscopy (KPFM) to investigate the micro-scale morphology and surface potential (SP) of the BA2MA3Pb4I13 films. In additionally, a Xenon laser source was adopted to realize the in-situ scanning of the light response of the perovskite film. The obvious increase in surface potential values in the same scanning area before and after white light illumination indicated the emergence of photo-generated charge carriers. Based on the unique photophysical properties and form formation features of the hot-cast BA2MA3Pb4I13 films, we fabricated the 2D perovskite solar cells (PSCs) with an efficiency of 10.95%. As a result, the in-situ KPFM is capable to serve as an effective approach to investigating the charge carrier behaviors in the 2D perovskites for photovoltaic applications.

Integrated Perovskite/Organic Photovoltaics with Ultrahigh Photocurrent and Photoresponse Approaching 1000 nm

To enhance the photoresponse of commonly used perovskite materials in the near‐infrared (NIR) region, a fused‐ring electron acceptor (F8IC) with strong NIR absorption and high electron mobility is used to blend with a narrow‐bandgap polymer donor (PTB7‐Th) to construct an organic bulk heterojunction (OBHJ), and this OBHJ is then integrated with the perovskite solar cells (PSCs). The integrated perovskite/OBHJ solar cells exhibit a strong photoresponse approaching 1000 nm and an ultrahigh short‐circuit current density of 28.2 mA cm−2, which is much higher than that of traditional PSCs and organic solar cells.

Defect-Engineering-Enabled High-Efficiency All-Inorganic Perovskite Solar Cells.

The emergence of cesium lead iodide (CsPbI3 ) perovskite solar cells (PSCs) has generated enormous interest in the photovoltaic research community. However, in general they exhibit low power conversion efficiencies (PCEs) because of the existence of defects. A new all-inorganic perovskite material, CsPbI3 :Br:InI3 , is prepared by defect engineering of CsPbI3 . This new perovskite retains the same bandgap as CsPbI3 , while the intrinsic defect concentration is largely suppressed. Moreover, it can be prepared in an extremely high humidity atmosphere and thus a glovebox is not required. By completely eliminating the labile and expensive components in traditional PSCs, the all-inorganic PSCs based on CsPbI3 :Br:InI3 and carbon electrode exhibit PCE and open-circuit voltage as high as 12.04% and 1.20 V, respectively. More importantly, they demonstrate excellent stability in air for more than two months, while those based on CsPbI3 can survive only a few days in air. The progress reported represents a major leap for all-inorganic PSCs and paves the way for their further exploration in order to achieve higher performance.

Design and Synthesis of 1D-Polymeric Chain Based [(CH3NH3)3Bi2Cl9]n Perovskite: A New Light Absorber Material for Lead Free Perovskite Solar Cells

Although traditional perovskite solar cells have made tremendous progress in terms of efficiency, the presence of toxic lead has restricted their commercialization. Herein, we report the first example of a facile synthesis and a newly designed highly stable lead free methylammonium bismuth chloride in the form of 1D-polymeric chain based perovskite. The formation of a 1D-polymeric chain with formula [(CH3NH3)3Bi2Cl9]n (1) has been authenticated by its single crystal X-ray diffraction (SCXRD) studies. The lead free 1 has been employed as an alternative to the traditional CH3NH3PbX3 perovskite with an excellent open circuit voltage of 430 mV.

Enhanced Performance and Photostability of Perovskite Solar Cells by Introduction of Fluorescent Carbon Dots.

Perovskite solar cells (PSCs) with high efficiency have recently received tremendous attention, but the stability under light irradiation, namely, photostability, of PSCs still represents a major obstacle that must be overcome before their practical applications can be used. The degeneration of perovskite under ultraviolet irradiation from sunlight is a major impacting factor. To solve this problem, in this work we introduce fluorescent carbon dots (CDs), which could effectively convert ultraviolet to blue light in the mesoporous TiO2 (m-TiO2) layer of the traditional PSCs. As a result, CD-based devices exhibit an improved power conversion efficiency (PCE) of 16.4% on average compared to 14.6% for bare devices, and the light stability of CD-based devices is highly enhanced. These devices can maintain nearly 70% of the initial efficiency after 12 h of full sunlight illumination, while the bare devices maintain only 20% of the initial efficiency. This work indicates that fluorescent down conversion based on CDs is a novel and effective approach to improve the performance and photostability of PSCs.