Perovskite Active Layer Research Articles

Effect of Perovskite Active Layer Thickness on the Performance of Photovoltaic Cells and Radiation Detectors

Effect of Perovskite Active Layer Thickness on the Performance of Photovoltaic Cells and Radiation Detectors

Pyrene‐Based Self‐Assembled Monolayer with Improved Surface Coverage and Energy Level Alignment for Perovskite Solar Cells

AbstractRecently, the efficiency of p‐i‐n perovskite solar cells drastically increased, a pivotal factor being the incorporation of self‐assembled monolayers (SAMs) as a hole‐transporting layer (HTL). SAMs offer many advantages over conventional HTLs, including minimal material requirements, low cost, and facile processing. Current research is mainly focused on the development of carbazole‐derived SAMs. However, the versatility of organic chemistry allows for the design of SAMs with alternative organic cores that may possess specific benefits. In this study, three novel SAMs are incorporated in p‐i‐n perovskite solar cells, each based on an aromatic core commonly used in organic semiconductors. The novel SAMs vary in their energy level alignment with the perovskite active layer. Optimal alignment is achieved with a pyrene‐based SAM (4PAPyr), resulting in solar cells that outperform the commercially available 2PACz. Moreover, due to improved surface coverage, the use of 4PAPyr leads to a significantly higher number of working solar cell devices when compared to 2PACz, which is of particular interest with regard to upscaling. After device optimization, a power conversion efficiency of 22.2% is achieved with 4PAPyr. This research underlines the importance of diversifying SAMs to unlock further advancements in perovskite solar cell efficiency and scalability.

Across‐Interface Effect of Alkylamine Salt on the Formation of Intermediate Phase and Defect Passivation in High‐Performance of Perovskite Solar Cells

AbstractHigh‐quality and low‐defect perovskite active layer (PVK) and electron transport layer (ETL) are essential for high‐performance perovskite solar cells (PSCs). Herein, an alkylamine salt, cyclohexylmethylammonium chloride (CMACl) is introduced into tin oxide (SnO2) ETL. CMACl, possessing protonated −NH3+ group and Cl− ions, not only effectively inhibits the aggregation of SnO2 colloids and enhances the quality of the ETLs, but also reduces and passivates the defects on ETLs. On the other hand, via the across‐interface effect of alkylamine salt by thermal diffusion, the CMACl‐PbI2 intermediate phase is formed and leads to the high quality of PVK, meanwhile, the defect on the buried interfaces and in the bulk of PVK are passivated by CMA+ and Cl− ions. Consequently, the CMACl‐modified PSC achieves a preeminent power conversion efficiency of 25.47% and excellent stability. This work demonstrates a facile and effective approach for synchronous optimization of ETL and PVK for high‐performance PSCs by across‐interface effect.

Plasmonic molybdenum carbide MXene nanosheets for highly efficient and stable perovskite solar cells

Besides the excellent metallic electrical conductivity, high carrier mobility, and high optical transmittance, the two-dimensional MXenes exhibiting impressive optical and plasmonic properties have been explored to photodiodes. However, their potential use of surface plasmons oscillating in perovskite solar cells has not been studied. Herein, we incorporate, for the first time, Mo2CTx MXene nanosheets with characteristic plasmonic absorption in the whole visible region into the perovskite active layer. First, the presence of Mo2CTx nanosheets in the perovskite film increases the perovskite grain size due to the decreased growth rate and passivation of the defects around the grain boundaries through strong interaction with undercoordinated Pb2+. Furthermore, with the help of the localized surface plasmon resonance effect of Mo2CTx nanosheets, the exciton binding energy in the perovskite absorber is reduced, which suggests the efficient exciton dissociation and enhanced charge separation. Consequently, Mo2CTx nanosheets based perovskite solar cell device exhibits a champion power conversion efficiency (PCE) of 24.05 %. It is worth noting that the unencapsulated devices demonstrate considerably improved stability, maintaining about 89.25 % of the initial PCE after aging in air for 3000 h. This fascinating strategy provides more opportunities of the functional MXene materials for the perovskite optoelectronics.

Single Layer of Crown Ether Enables Efficient, Stable, and Pb Leakage-Free Inverted Perovskite Solar Cells.

Significant challenges in ensuring long-term stability, addressing environmental safety issues, and improving efficiency have hindered the commercialization of inverted Pb-based halide perovskite solar cells (PeSCs). One reasonable approach to addressing these issues is to place an effective buffer layer between the perovskite active layer and the electrode. In this study, we demonstrate the use of crown ether, di-tert-butyl dibenzo-18-crown-6, as a single buffer layer to improve the efficiency, long-term stability, and environmental safety of PeSCs for the first time. The crown ether buffer layer suppressed Ag diffusion from the Ag metal electrodes, thereby improving the performance and lifetime of the device. In addition, it effectively captures Pb ions that may leak into the environment during the whole lifetime of devices, thereby enhancing the environmental safety of PeSCs. Furthermore, PeSCs incorporating crown ethers as buffer layers demonstrated enhanced stability in a nitrogen atmosphere and achieved a high power conversion efficiency of 22.8%. Consequently, this crown ether buffer layer offers an effective and straightforward strategy capable of achieving efficient, stable, and environmentally safe PeSCs.

Enhancing light absorption in ultra-thin perovskite solar cells using plasmonic gold nanoparticle clusters

Perovskite solar cells with ultra-thin absorber layers offer potential cost savings in manufacturing, but their reduced thickness can limit light absorption and efficiency. This work explores using plasmonic gold nanoparticles as a light-trapping strategy to compensate for lower absorption in ultra-thin perovskite devices. Numerical simulations investigate embedding 25 nm radius gold nanoparticles within the 200 nm thick perovskite active layer to boost optical absorption through near-field enhancement and light scattering effects. The solar cell structure incorporating these plasmonic nanoparticles achieves a substantially higher short-circuit current density of 23.10 mA cm−2 compared to 18.70 mA cm−2 for a reference cell without nanoparticles. This study provides design approaches for realizing high-efficiency yet cost-effective ultra-thin perovskite photovoltaics by harnessing plasmonic light-trapping techniques. The results display methodologies to improve photon absorption and power conversion in thin-film perovskite devices through strategic nanoparticle integration.

Efficient bifacial semi-transparent perovskite solar cells via a dimethylformamide-free solvent and bandgap engineering strategy

Semi-transparent perovskite solar cells (ST-PSCs) featuring high performance and light transmittance are highly desirable for building integrated photovoltaic (BIPV) applications. However, it is challenging to balance the device efficiency and transmittance due to the trade-off between light-harvesting capability and transparency of the perovskite active layer. Herein, we demonstrate a simple solvent- and bandgap-engineering strategy to effectively enhance film transparency of (FAPbI3)0.85(MAPbBr3)0.15 perovskite while simultaneously preserving its decent light-harvesting capability. N-methyl-2-pyrrolidone (NMP) as the solvent of the perovskite precursor effectively confines the growth of perovskite grains, leading to reduced light-scattering and enhanced average visible transparency (AVT) of the perovskite layer (over 28 %). Meanwhile, the NMP solvent promotes the growth of highly crystalline perovskite films with excellent light-harvesting capability, largely benefiting from stable intermediate adducts due to its intrinsic nature as a coordinative Lewis base. Further bandgap engineering of the perovskite light adsorber (1.6 eV) leads to the design of highly efficient bifacial ST-PSCs, achieving a power conversion efficiency of 15.58 % when illuminated from the conductive glass side and 9.67 % from the top electrode side, both under 1 sun illumination. The best-performing devices also show great promise for indoor applications with an efficiency of 25 % under 1000 lux indoor light illumination.

Enhancing the Humidity Stability of Perovskite Films through Interfacial Modification with Differentiated Hydrophilic Organics.

Preparing high-quality perovskite films is a decisive step toward realizing highly efficient and stable perovskite solar cells (Pero-SCs). Water is a key factor affecting the stability of the Pero-SCs. Here, the widely used water adsorbents chitosan, sorbitol, and sodium hyaluronate (NaHA) were used as hydrophilic layers on the upper interface of the perovskite to form a barrier against water. The water adsorbents also passivated defects on the surface of the perovskite active layer due to their -OH and -COOH functional groups. The NaHA-modified devices showed the best power conversion efficiency (PCE) (PCE = 21.74%). Although the NaHA-modified Pero-SCs showed optimal photovoltaic performance, the stability of the modified devices decreased due to the strong water adsorption ability of NaHA, while with moderate water adsorption ability sorbitol-modified devices exhibited good stability and PCE. The devices were tested in the dark and room temperature at different humidity levels for 800 h. At low humidity (25% ± 5% RH), the PCEs of the sorbitol- and NaHA-modified devices were maintained at 80% and 71% of the initial values, respectively. At high humidity (75% ± 5% RH), the PCE was maintained at 64% and 23% of the initial values, respectively. This work provides an avenue to select adsorbents with suitable water absorption ability as the interface modification layer, thus reducing the water erosion of perovskite films and obtaining highly stable inverted Pero-SCs.

Solar brilliance unleashed: Maximizing performance of novel carbon-based Rb-doped CsSnI3 perovskite solar cells by gradient doping

The commercialization of state-of-the-art perovskite solar cells (PSCs) is hindered by lead toxicity, high production costs, and stability issues. The current study addresses these challenges by exploring lead-free Rb-doped CsSnI3 perovskite with carbon-based materials. Herein, the impact of Rb-doping in CsSnI3 perovskite has been thoroughly investigated on its structural, electrical, and optical properties via DFT studies. The results show that the incorporation of Rb-cation into CsSnI3 significantly enhances the stability of the perovskite active layer (PAL), addressing the major challenge of degradation under environmental conditions. Further, DFT results are used to investigate the potential of Cs0.75Rb0.25SnI3 as a PAL in device architecture FTO/ETL/Cs0.75Rb0.25SnI3/CNTs/C via SCAPS-1D with different electron transport layer (ETL) and carbon-based hole transport layer and back contact. Simulation results show that among different ETLs, WO3 demonstrates the best performance. Further, we have employed a gradient doping (GD) strategy in PAL, dividing it into two sub-layers of thickness 200 nm each with different doping concentrations in the simulated device FTO/WO3/CsRbSnI3/CNTs/C. The aim of implementing GD is to strengthen the electric field and improve the energy band alignments which helps in reducing interfacial recombination. Besides, the impact of band-gap, interfacial defects, hysteresis effect, and C–V and C–F analysis are examined. The results reveal that at doping gradient G = 300, the device attains the best PCE of 19.05% with Eg of 1.32 eV (PAL-1) and 1.22 eV (PAL-2). This study can serve as a benchmark for developing high-performance and low-cost CsRbSnI3-based PSCs utilizing a gradient doping strategy.

A Double Compatibilization Strategy To Boost the Performance of p-i-n Solar Cells Based on Perovskite Deposited in Humid Ambient Air.

Formamidinium lead iodide (FAPI) represents the most promising perovskite for single junction solar cells, exhibiting an impressive performance when deposited in a controlled nitrogen environment. In order to foster the real-world application of this technology, the deposition of FAPI in ambient air is a highly desirable prospect, as it would reduce fabrication costs. This study demonstrates that the wettability of FAPI precursors on the hole transporting layers (HTL) used to fabricate inverted p-i-n solar cells is extremely poor in ambient air, hampering the realization of a perovskite active layer with good optoelectronic quality. To address this issue, herein, a double compatibilization method is developed, which results in the attainment of remarkable performance, exceeding 21%, representing one of the highest reported efficiencies for FAPI solar cells fabricated in humid ambient air. The incorporation of a small quantity of anionic surfactant, comprising a hydrocarbon tail and a polar headgroup, sodium dodecyl sulfate (SDS), in the perovskite solution and an ultrathin layer of alumina nanoparticles on the HTL, results in a significant improvement in the wettability of the FAPI solution. This enables the reproducible deposition of highly homogeneous perovskite films with complete coverage and excellent optical and optoelectronic quality. Furthermore, devices based on FAPI with SDS exhibit enhanced stability, retaining 98% of their initial efficiency after 40 h of continuous illumination.

Sustainable Mixed-Halide Perovskite Resistive Switching Memories Using Self-Assembled Monolayers as the Bottom Contact.

The complex ionic-electronic conduction in mixed halide perovskites enables their use beyond von Neumann architectures implemented in resistive switching memory devices. Although device fabrication based on perovskite compounds involves solution-processing at low temperatures, reducing further fabrication costs by eliminating expensive materials can improve their compatibility with upscalable deposition techniques. Notably, the substrate on which the perovskite active layer is developed has been reported to severely affect its quality and thus the overall device performance. Hereby, we demonstrate the sustainable manufacturing of memristive perovskite solar cells by replacing the expensive poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) that serves as a hole transporting layer (HTL) with a self-assembled monolayer (SAM), namely [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz). Multiple sequential memristive current-voltage characteristics of single devices are reported, and average data of multiple reference and targeted devices are compared. Resistive switching memory devices based on SAM exhibit improved performance having reduced average SET voltage values and narrower statistical variation compared to reference devices with PTAA. It is shown that both PTAA and SAM based devices exhibit high ON/OFF ratio of about 103 operating at low switching electric fields. Replacing an expensive polymer-based HTL with this approach reduces fabrication costs compared to PTAA.

A comparative simulation study of light–matter coupling in 1D photonic crystals with 2D perovskite active layer

Light–matter interaction operating in the strong coupling regime offers wide prospects of applications going from nano-photonics to quantum communications. The most practical implementations are to embed the active matter into Fabry–Perot microcavities or photonic crystals. In this work we focus on the strong coupling of two-dimensional (2D) perovskite in 1D grating waveguide. We use rigorous coupled wave analysis to simulate electromagnetic wave confinement in the 1D waveguide. Various sets of waveguide geometrical parameters are examined to achieve the strong coupling regime for three different configurations of the active layer in the waveguide. To extract quantitatively the relevant physical parameters, such as strength of light–matter interaction, we develop a Hamiltonian formalism to reproduce results obtained by simulation. It is shown that the strongest interaction is to have the active layer inserted in the main slab of the waveguide. It is, however, still weaker by about 20% as compared to the use of Fabry–Perot microcavities.

Enhancing photovoltaic performance through interfacial Engineering: A comparative analysis of bismuth iodide (BiI3) and Cs2BiAgI6 as interlayer materials in the design of perovskite solar cells

In this study, solar cell capacitance simulator (SCAPS) was employed to investigate the impact of bismuth iodide (BiI3) and Cs2BiAgI6on the performance of perovskite solar cell. We analyze the influence of charge carrier mobility on perovskite,IL thickness and effect of series and shunt resistance on the behavior of the cell.Results show that adding a thin layer at the interface between the Perovskite active layer and HTL effectively improve hole extraction by defect passivation,which in turn improve device performance in comparison to a common reference design. Our findings reveal that the structure with Cs2BiAgI6 was more efficient where the optimum configuration was (PSi/CuO/Cs2BiAgI6/perovskite/ ZnO) with power conversion efficiency(PCE) of 19.82 %, Fill Factor (FF) of 68,04 %, open circuit voltage (Voc)of 1,438 V and, Short circuit current (Jsc) of 20,2519 mA. cm − 2. Levelized cost of electricity (LCOE) of PSCs was estimated using the compute unit costs, it was found to be 4.41 US cents / kWh with a lifetime of ten years,below then the cost of conventional PSC devices.

Optical terahertz metamaterial switch controlled via high-stability CsPbBr3 microcrystals.

Dynamic control of terahertz metamaterials using thin organic perovskite active layers has been extensively researched. However, the preparation of organic perovskite devices requires strict environmental conditions, and the devices are prone to hydrolysis in air, which reduces performance. Herein, we report an optical terahertz metamaterial switch controlled via hybridization with high-stability CsPbBr3 microcrystals prepared through precipitation from a water-dimethylformamide (DMF) mixed-solution. Under light excitation, a modulation factor of 24% was achieved based on the photoelectric and photothermal effects of the CsPbBr3 microcrystals. After exposure to air for four months, the modulation factor remained essentially unchanged, demonstrating the exceptional stability of the system generated. Following the integration of CsPbBr3 microcrystals with the metamaterial, a frequency-shift of its dipole resonance and switching of Fano resonance was achieved, providing a novel approach to dynamic control of terahertz waves.

Perovskite solar cell enhancement by tin oxide modification via doping sodium trifluoroacetate

Recently, perovskite solar cells have attracted a lot of attention due to their great potential to get high performance and favorable features. One of the most dealt with electron transport layers (ETL) in perovskite solar cells is tin(IV) oxide because of its favorable band alignment in comparison with perovskite active layers’ energy band and high charge mobility. Nevertheless, this famous ETL layer has some disadvantages that until now researchers are trying to solve them and the large amount of surface trap density of tin oxide crystals is one of these adverse features. In this research, we offer a new method to enhance the mobility and decrease the surface trape density of the tin oxide crystals ETL by doping sodium trifluoroacetate. By doping sodium trifluoroacetate to ETL Tin oxide-based ETL, the amount of oxygen vacancies in the ETL film shows great decrement and results in enhancement of the electron extraction in the perovskite solar cell. By using doped tin oxide-based ETL in the perovskite solar cell, we were able to achieve 19.51 % of solar cell efficiency with remarkable enhancement in comparison with tin oxide-based ETL without doping.

An optical study on the enhanced light trapping performance of the perovskite solar cell using nanocone structure

Photon management strategies are crucial to improve the efficiency of perovskite thin film (PTF) solar cell. In this work, a nano-cone (NC) based 2D photonic nanostructure is designed and simulated aiming at achieve superior light trapping performance by introducing strong light scattering and interferences within perovskite active layer. Compared to the planar PTF solar cell, the NC nanostructured device with 45 degrees half apex angle obtains highest short-circuit current density, which improved over 20% from 15.00 mA/cm2 to 18.09 mA/cm2. This work offers an alternative design towards effective light trapping performance using 2D photonic nanostructure for PTF solar cell and could potentially be adopted as the nano-structuring strategy for the future perovskite solar cell industry.

Impact of Buried Interface Texture on Compositional Stratification and Ion Migration in Perovskite Solar Cells

AbstractDespite the striking increase in the power conversion efficiency (PCE) of lead‐based perovskite solar cells (PSCs), their poor operational stability impedes their commercialization. Among the various factors that influence device stability, ion migration has been identified as a key driver of degradation. In this work, the focus is on studying ion migration‐induced degradation in inverted architecture PSCs, which employ either a thin polymer layer or a self‐assembled monolayer (SAM) for hole extraction. It is demonstrated that the difference in texture imposed by the use of these hole transport layers (HTL) is an important and thus far inconspicuous factor that impacts ion migration, and consequently device stability. By investigating the buried interface in detail, it is revealed that its texture has a strong impact on the vertical compositional stratification in the perovskite active layer. By monitoring bias‐induced ion migration in devices with different hole extraction layers, it is demonstrated that the smooth polymer‐based HTL results in a higher degree of ion migration than the rough SAM HTL, corresponding to a stronger degradation in the former. These results further indicate that the use of SAMs for hole extraction is a promising strategy to suppress ion migration and improve device efficiency.

Residual Stress Mitigation in Perovskite Solar Cells via Butterfly-Inspired Hierarchical PbI2 Scaffold.

Residual stress in metal halide perovskite films intimately affects the photovoltaic figure of merit and longevity of perovskite solar cells. A delicate management of the crystallization kinetics is critical to the preparation of high-quality perovskite films. Only very limited methods, however, are available to regulate the residual stress of a perovskite film in a controllable manner, particularly for a perovskite film fabricated by a two-step method. Here, we demonstrate the construction of a hierarchical PbI2 scaffold inspired by Archaeoprepona demophon butterfly by combining an interlayer guided growth of porous structure and nanoimprinting. The hierarchically structured PbI2 that emulates the physical structure of the butterfly wing scale permits unimpeded permeation of organic amine salts and sufficient space for volume expansion during the crystallization process, accompanied by preferential perovskite growth of a defectless (001) crystal plane. The optimized perovskite film outperforms the control with reduced residual stress and defect density. Consequently, perovskite solar cells with a respectable power conversion efficiency reaching 23.4% (certified 23%) and an impressive open-circuit voltage of 1.184 V can be achieved. The target device can maintain 80% of initial efficiency after maximum power point tracking under illumination for 700 h. This work expands the range of engineering toward PbI2 by exploring a simultaneously tailored morphology and crystallinity and highlights the significance of a hierarchical PbI2 scaffold as an alternative choice to mitigate residual stress in a two-step processed perovskite active layer and boost the longevity of perovskite solar cells.

Counter-Doping Effect by Trivalent Cations in Tin-Based Perovskite Solar Cells.

Tin (Sn) -based perovskite solar cells (PSCs) normally show low open circuit voltage due to serious carrier recombination in the devices, which can be attributed to the oxidation and the resultant high p-type doping of the perovskite active layers. Considering the grand challenge to completely prohibit the oxidation of Sn-based perovskites, a feasible way to improve the device performance is to counter-dope the oxidized Sn-based perovskites by replacing Sn2+ with trivalent cations in the crystal lattice, which however is rarely reported. Here, the introduction of Sb3+, which can effectively counter-dope the oxidized perovskite layer and improve the carrier lifetime, is presented. Meanwhile, Sb3+ can passivate deep-level defects and improve carrier mobility of the perovskite layer, which are all favorable for the photovoltaic performance of the devices. Consequently, the target devices yield a relative enhancement of the power conversion efficiency (PCE) of 31.4% as well as excellent shelf-storage stability. This work provides a novel strategy to improve the performance of Sn-based PSCs, which can be developed as a universal way to compensate for the oxidation of Sn-based perovskites in optoelectronic devices.

One-Stone-for-Two-Birds Method to Improve the SnO2 Layers for High Power-per-Weight Flexible Perovskite Solar Cell Mini-modules.

Maintaining the power conversion efficiency (PCE) of flexible perovskite solar cells (fPSCs) while decreasing their weight is essential to utilize their lightweight and flexibility as much as possible for commercialization. Strengthening the interfaces between functional layers, such as flexible substrates, charge transport layers, and perovskite active layers, is critical to addressing the issue. Herein, we propose a feasible and one-stone-for-two-birds method to improve the electron transport layer (ETL), SnO2, and the interface between the ETL and perovskite layer simultaneously. In detail, poly(acrylate ammonium) (PAAm), a low-cost polymer with a long chain structure, is added into the SnO2 aqueous solution to reduce the aggregation of SnO2 nanoparticles, resulting in the deposition of a conformal and high-quality ETL film on the tin-doped indium oxide film surface. Simultaneously, PAAm addition can effectively regulate the crystallization of the perovskite films, strengthening the interface between the SnO2 film and the buried surface of the perovskite layer. The outstanding PCEs of 22.41% on small-scale fPSCs and 18.54% on fPSC mini-modules are among the state-of-the-art n-i-p type fPSCs. Moreover, the fPSC mini-module on the 20 μm-thick flexible substrate shows a comparable PCE with that of the fPSC mini-module on the 125 μm-thick flexible substrate, exhibiting a high power-to-weight of 5.097 W/g. This work provides an easy but essential direction for further applications of fPSCs in diverse scenarios.