Printable Mesoscopic Perovskite Solar Cells Research Articles

Room-Temperature Ripening Enabled by Hygroscopic Salts for Hole-conductor-Free Printable Perovskite Solar Cells with Efficiency Over 20 .

Solution-processed perovskite films generally possess small grain sizes and high density of grain boundaries, which intensify non-radiative recombination of carriers and limit the power conversion efficiency (PCE) of solar cells. In this study, we report the room-temperature ripening enabled by the synergy of hygroscopic salts and moisture in air for efficient hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs). Treating perovskite films with proper hygroscopic salts in damp air induces obvious secondary recrystallization, which coarsens the grains size from hundreds of nanometers to several micrometers. It's proposed that the hygroscopic salt at grain boundaries could absorb moisture and form a complex which could not only serve as mass transfer channel but also assist in the dissolution of perovskite grains. This activates mass transfer between small grains and large grains since they possess different solubilities, and thus ripens the perovskite film. Consequently, p-MPSCs treated with the hygroscopic salt of NH4SCN show an improved power conversion efficiency of 20.13 % from 17.94 %, and maintain >98 % of the initial efficiency under maximum power point tracking at 55±5 °C for 350 hours.

Decylammonium sulfate post-treatment for efficient hole-conductor-free printable perovskite solar cells with reduced voltage loss

Hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs) have attracted widespread attention for their low cost, up-scalability, and exceptional stability. However, the high defect density of perovskite and the absence of interfacial barrier layer between perovskite and carbon electrode cause profound open-circuit voltage (VOC) loss, which results in uncompetitive power conversion efficiency (PCE). Herein, an anion-cation synergy of decylammonium sulfate (DA2SO4) is utilized for suppressing VOC loss of p-MPSCs via a facile post-treatment method. DA+ cations transform the perovskite adjacent to carbon electrode into wide-bandgap 2D perovskite for blocking electrons, while the SO42− anions interact with undercoordinated lead centers for reducing defect density. As a result, the modified device delivers an enhanced PCE from 17.78% to 19.59%, with an improved VOC from 0.98 V to 1.06 V. Meanwhile, the modified device without any encapsulation exhibits excellent moisture stability with the PCE remained almost 99% of the initial value after 528 h aging in 75% RH air at room temperature.

Modulating Dual Functionalities of Hydrazide Derivatives for Iodide Oxidation Suppression and Defect Passivation in Printable Mesoscopic Perovskite Solar Cells

AbstractThe oxidation of iodide ions during annealing in air and rich defects generated at crystal terminations in perovskite are major limitations for achieving high photovoltaic performance in printable mesoscopic perovskite solar cells (p‐MPSCs). Here, the dual role of hydrazide derivatives in inhibiting iodide oxidation and passivating crystal termination defects is reported and how the dual role is affected by the substituent is studied. It's found that varying the hydrazide derivative from formylhydrazine (FH) to benzhydrazide (BH) and then to 4‐tert‐butylbenzhydrazide (TBBH) by introducing phenyl and 4‐tert‐butylphenyl substituents enhances the electron donating ability of hydrazides due to substituent electronic effect. The tailored hydrazides present enhanced iodide oxidation suppression and defect passivation capabilities, which lowers the trap density of perovskite in p‐MPSCs significantly. As the most effective additive, TBBH improves the power conversion efficiency of the p‐MPSC from 18.66% to 20.30%, and the resulted device maintains 90% of its initial efficiency after 500 h tacking at maximum power point at 55 ± 5 °C under simulated 1 sun illumination.

In Situ Reconstruction Post‐Treatment for Efficient Carbon‐Based Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

AbstractPerovskite solar cells are regarded as the most promising and disruptive photovoltaic of the new generation. Carbon‐based hole‐conductor‐free printable mesoscopic perovskite solar cells (p‐MPSCs) with three mesoscopic layers have garnered considerable interest owing to their simple manufacturing process and cost‐effective raw materials, signaling the potential for commercialization. However, the energy level mismatch between the perovskite and the carbon electrode as well as defects at perovskite grain boundaries inevitably lead to additional non‐radiative carrier recombination and large voltage loss. In this study, a facile in situ reconstruction post‐treatment approach is employed to integrate lead sulfide (PbS) and the two‐dimensional (2D) perovskite K2PbI4 into the mesoporous scaffolds of p‐MPSCs. In this way, grain boundary defects are effectively passivated and the ion migration is suppressed by introducing 2D perovskite K2PbI4 at grain boundaries. Besides, the incorporation of PbS leads to the downward shift of the Fermi level for perovskite, which enhances hole collection within the device by optimizing band alignment at the perovskite/carbon interface. Consequently, an improved efficiency exceeding 20% is achieved for p‐MPSCs with no significant performance degradation observed over a storage period of 235 days. This strategy provides a facile and novel approach toward fabricating highly efficient and stable p‐MPSCs.

Tri-Step Water-Assisted Strategy for Suppressing Cs4PbBr6 Phase in Printable Carbon-Based CsPbBr3 Solar Cells to Achieve High Stability.

Often deemed the "natural nemesis" of perovskites, water molecules have been largely circumvented by the majority of researchers in the field of perovskite solar cells. This has resulted in significant hurdles in investigating the beneficial impacts of water molecules on perovskite crystallization. Herein, it is found that by utilizing ethanol with minimal water content and subjecting all-inorganic perovskite to three distinct annealing temperatures within the same solvent, the residual CsBr can be effectively removed, and the formation of the Cs4PbBr6 phase can be curtailed. By selecting an optimal water content, substantial improvements are observed in the crystalline quality of CsPbBr3, the perovskite/carbon interface, and the mesoporous filling effect. The Urbach energy (Eu) is reduced from 38.96 to 35.59meV, and the defect density decreased from 4.16×1014 to 3.39×1014cm-3. As a result, the power conversion efficiency (PCE) improved from 7.55% in the control group to 9.37%. Under severe environmental conditions with a temperature (T) of 85°C and a relative humidity (RH) of 40%, tracking tests over 1200h retained 89.3% of the initial PCE. This research signifies a breakthrough in the fabrication of highly stable and efficient all-inorganic printable mesoscopic perovskite solar cells.

Implementing a Two‐in‐One Defect Passivation Strategy Utilizing CsX for High‐Performance Printable Carbon‐Based Perovskite Solar Cells

AbstractIn the rapidly advancing realm of perovskite solar cells, the rectification of defects has surfaced as a crucial scientific challenge. The control over defect states, especially in printable mesoscopic perovskite solar cells (p‐MPSCs), is hindered by the complexities of screen‐printing technology. Here a novel “two‐in‐one” defect passivation strategy is presented, through doping TiO2 paste with cesium halide salts (CsX, where X = F, Cl, Br, I) to integrate all‐inorganic Cs halides, particularly CsF, into the electron transport layer in p‐MPSCs. Owing to the robust interaction between F− ions and TiO2 compared to Cs+ ions, and the inability of F− to infiltrate the perovskite lattice, F− and Cs+ play distinct roles starting from the buried interface of the p‐MPSCs. Specifically, F− can rectify the oxygen vacancies on the TiO2 surface, thus alleviating the residual stress at the perovskite's buried interface. Simultaneously, Cs+ diffuses to the top perovskite and mends the methylamine vacancies. As a result, the PCE of the optimal device, based on F‐doped TiO2, witnesses a significant improvement from 16.18% (control) to 18.24%. The two‐in‐one strategy utilizing CsX from the buried interface can well realize the all‐inorganic defect rectification, thereby offering a promising prospect for the enhancement of p‐MPSC performance.

Crystallization Control Assists Annealing‐Free Fabrication of Printable Mesoscopic Perovskite Solar Cells with Power Conversion Efficiency over 17%

The one‐step drop‐casting for preparing perovskite films in three‐layer mesoporous for printable mesoscopic perovskite solar cells always results in insufficient filling of mesopores. A binary solvent based on 2‐methoxyethanol (2‐ME) and 1‐methyl‐2‐pyrrolidone (NMP) offers a method suitable for annealing‐free to prepare dense perovskite films in mesopores. The crystallization process of perovskite films in mesopores can be adjusted by the content of NMP in the solvent. The introduction of NMP enhances the density of the perovskite film based on the binary solvent system, optimizing the contact between the perovskite film and the mesoporous scaffold. When the ratio of 2‐ME to NMP is 9:1, the optimal device achieves impressive performance metrics, including a power conversion efficiency (PCE) of 17.28%, an open‐circuit voltage of 0.98 V, a short‐circuit current of 23.80 mA cm−2, and a fill factor of 74.08%. This represents the highest PCE achieved to date in the annealing‐free preparation of perovskite films for printable mesoscopic perovskite solar cells. Furthermore, devices based on this binary solvent system exhibit remarkable stability, with almost no loss in efficiency even after 120 days of storage in an air environment without encapsulation.

Bifunctional passivation by lewis-base molecules for efficient printable mesoscopic perovskite solar cells

Printable mesoscopic perovskite solar cells (PM-PSCs) possess notable merits in terms of cost-effectiveness, easy manufacturing, and large scale applications. Nevertheless, the absence of a hole transport layer contributes to the exacerbation of carrier recombination, and the defects between the perovskite and electron transport layer (ETL) interfaces significantly decrease the efficiency of the devices. In this study, a bifunctional surface passivation approach is proposed by applying a thioacetamide (TAA) surfactant on the mesoporous TiO2 interface. The results demonstrate that TAA molecules could interact with TiO2, thereby diminishing the oxygen vacancy defects. Additionally, the amino group and sulfur atoms in TAA molecules act as Lewis base to effectively passivate the uncoordinated Pb2+ in perovskite and improve the morphology of perovskite, and decrease the trap-state density of perovskite. The TAA passivation mechanism improves the alignment of energy levels between TiO2 and perovskite, facilitating electron transport and reducing carrier recombination. Consequently, the TAA-passivated device achieved a champion power conversion efficiency (PCE) of 17.86% with a high fill factor (FF) of 79.16% and an open-circuit voltage (VOC) of 0.971 V. This investigation presents a feasible strategy for interfacial passivation of the ETL to further improve the efficiency of PM-PSCs.

Efficient Carbon‐Based Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells via a Multifunctional Fluorinated Molecule

AbstractBenefiting from their simple and cost‐effective fabrication procedures, printable mesoscopic perovskite solar cells (p‐MPSCs) exhibit substantial potential for large‐scale production. In p‐MPSCs, the thickness of the perovskite filled in the TiO2 and ZrO2 mesoporous layers is ≈3 µm. Therefore, the perovskite crystallization process is more intricate and challenging in the mesoporous structure than the general planar thin film (0.3–0.5 µm). In this work, a multifunctional fluorinated molecule is applied to work as an additive to improve the perovskite crystallization, enhance the device efficiency, and elevate the operational stability. This additive forms robust coordination between its carbonyl groups and uncoordinated Pb2+, thereby effectively passivating defects. The hydrophobic properties of the fluorinated molecule contribute to the device's water‐resistant capability and long‐term operational stability. With these synergistic effects, the power conversion efficiency (PCE) of small‐area cells (0.1 cm2) reaches 20.15% under 1 sun illumination. Large‐area modules (56.4 cm2) are fabricated and exhibit a PCE of 15.41%.

Dual Defect Passivation at the Buried Interface for Printable Mesoscopic Perovskite Solar Cells with Reduced Open-Circuit Voltage Loss.

Numerous defects exist at the buried interface between the perovskite and adjacent electron transport layers in perovskite solar cells, resulting in severe non-radiative recombination and excessive open-circuit voltage (VOC) loss. Herein, a dual defect passivation strategy utilizing guanidine sulfate (GUA2SO4) as an interface modifier is first reported. On the one hand, the SO4 2- preferentially interacts with Pb-related defects, generating water-insoluble lead oxysalts complexes. Additionally, GUA+ diffuses into the perovskite and induces the formation of low-dimensional perovskite. These reactions effectively suppress trap states at the buried interface and perovskite boundaries in printable mesoscopic perovskite solar cells (p-MPSCs), thus increasing the carrier lifetime. Meanwhile, GUA2SO4 optimizes the interface energy band alignment, thus accelerating the charge extraction and transfer at the buried interface. This synergistic effect of trap passivation and interface energy band alignment modulation is strongly demonstrated by an increase in average VOC of 70mV and the power conversion efficiency improvement from 17.51% to 18.70%. This work provides a novel approach to efficiently improve the performance of p-MPSCs through dual-targeted defect passivation at the buried interface.

Design and upgrade of mesoporous perovskite solar cells

In recent years, there has been notable progress in the development of perovskite solar cells (PSCs), marked by significant advancements in efficiency, stability, and scalability. Among different device architectures and technical routes, mesoporous perovskite solar cells (MPSCs) based on TiO2/ZrO2/carbon scaffold and screen-printing fabrication process have shown unique advantages for mass production and commercialization due to the low material cost and scalable fabrication process. Through efforts on material optimization, interface engineering, and device design, the power conversion efficiency of MPSCs has steadily increased from the initial 6.64 ​% in 2013 to current 22.22 ​%. Attributing to the screen-printing-based fabrication process, printable mesoscopic PSCs have enabled large-area devices, from mini-modules to modules, and solar panels. In this review, we discuss the development and latest advances of MPSCs, and provide outlooks for further improving the performance of this promising photovoltaic technology.

Electron injection and defect passivation for high-efficiency mesoporous perovskite solar cells.

Printable mesoscopic perovskite solar cells (p-MPSCs) do not require the added hole-transport layer needed in traditional p-n junctions but have also exhibited lower power conversion efficiencies of about 19%. We performed device simulation and carrier dynamics analysis to design a p-MPSC with mesoporous layers of semiconducting titanium dioxide, insulating zirconium dioxide, and conducting carbon infiltrated with perovskite that enabled three-dimensional injection of photoexcited electrons into titanium dioxide for collection at a transparent conductor layer. Holes underwent long-distance diffusion toward the carbon back electrode, and this carrier separation reduced recombination at the back contact. Nonradiative recombination at the bulk titanium dioxide/perovskite interface was reduced by ammonium phosphate modification. The resulting p-MPSCs achieved a power conversion efficiency of 22.2% and maintained 97% of their initial efficiency after 750 hours of maximum power point tracking at 55 ± 5°C.

Molecular Symmetry of Small-Molecule Passivating Agents Improves Crystal Quality of Perovskite Solar Cells.

Direct interaction with the defect sites of perovskite, functional groups have become the focal point of attention as passivating agents. However, the molecular parent nucleus determines the overall physical properties of the molecule, including the push-pull electronic characteristics of the functional groups, which poses significant challenges in terms of selectivity. Here, we discovered that the binary acid structure based on thiophene as the parent nucleus, due to changes in molecular symmetry, caused significant changes in the molecular dipole moment, resulting in significant changes in the passivation effects on under-coordinated Pb2+ in perovskite solar cells. For the axially symmetric thiophen-2,5-dicarboxylic acid (TPDC), the high dipole moment formed a concentrated surface negative potential on the carboxyl group, showing significant superiority over the centrally symmetric thieno[3,2-b] thiophene-2,5-dicarboxylic acid (TTDC) in forming high-quality perovskite crystals, suppressing charge recombination, enhancing effective charge transport, and raising internal electric fields. The power conversion efficiencies of the fully printable mesoscopic perovskite solar cells based on TPDC and TTDC were 17.15 % and 14.79 %, respectively, exhibiting important research value in the field of small molecule passivation mechanism research.

Room-Temperature Processed Annealing-Free Printable Carbon-Based Mesoscopic Perovskite Solar Cells with 17.34% Efficiency.

Carbon-based printable mesoscopic perovskite solar cells (MPSCs) have promising commercial development due to the use of easily scalable printing processes and low-cost carbon material electrodes. Simplifying the preparation process of MPSCs will undoubtedly contribute to their practical application. Here, we demonstrate that efficient and stable MPSCs can be prepared at room temperature without annealing by using low boiling point 2-methoxyethanol (2-ME) and strongly coordinated N-methyl-2-pyrrolidone (NMP) as a novel mixed solvent under the synergistic effect of ammonium chloride (NH4Cl). The results show that the 2-ME/NMP mixed solvent can generate an optimized coordination environment so that uniform nucleation and crystallization of perovskites in mesopores can be achieved at room temperature without annealing by forming uniform small-sized colloids in the precursor solution. Moreover, our work for the first time introduces NH4Cl as a crystallization modulator during a room-temperature annealing-free process, effectively regulating the crystallization behavior of perovskite in mesopores and obtaining high-quality perovskites. Finally, MPSCs prepared synergistically by a room-temperature annealing-free process based on a low boiling point 2-ME/NMP mixed solvent and NH4Cl modulator achieved a champion power conversion efficiency of 17.34% while demonstrating excellent long-term air stability for over half a year. This work provides a new approach to simplifying the preparation process of MPSCs and preparing efficient and stable MPSCs through a room-temperature annealing-free process.

Nanoscale Pumping Effect of Perovskite via Supported Bilayer Electron Transport Layer for Efficient Printable Mesoscopic Solar Cells

Recently, enhancing the photovoltaic performance of printable mesoscopic perovskite solar cells (p‐MPSCs) poses a significant challenge, particularly in improving the diffusion of perovskite precursor solutions during device assembly. In this research, effective gap‐driven diffusion of the precursor solution perovskite is successfully achieved, leading to the formation of well‐filled and crystallized perovskite through TiO2 nanorod arrays. By incorporating upper‐layer TiO2 nanoparticles, a bilayer electron transport layer with dual crystal phase is developed, establishing a cascaded energy level structure that exhibits superior capabilities in electron collection and directional transport. The effective suppression of nonradiative recombination and efficient charge transfer result in notable enhancements in both open‐circuit voltage and short‐circuit current density. Consequently, the power conversion efficiency of p‐MPSCs devices based on MAPbI3 γ‐butyrolactone solution increases from 14.32% to 16.07% (highest reported value in the literature is 16.21%). These findings highlight a novel interface engineering approach for the fabrication of high‐performance p‐MPSCs devices.

Tailoring lattice chlorine in perovskite through dual-additive engineering for enhanced photovoltaic performance

This research investigates chloride residues originating from MACl in perovskite solar cells. A dual-additive strategy employing MACl and DMACl effectively mitigates it in printable mesoscopic perovskite solar cells, leading to enhanced efficiency.

Additive enhanced passivation and lead immobilization of waste expandable polystyrene for perovskite photovoltaics

Every year, millions of tons of expandable polystyrene (EPS) are released into the environment, posing significant environmental pressure due to its slow natural decomposition that takes hundreds of years. Current recycling methods for EPS include organic solvent dissolution and recycling, composite material preparation, and building decoration. However, these methods are costly and have low utilization value. In this study, we propose an innovative approach by incorporating waste EPS into the assembly process of printable mesoscopic perovskite solar cells (p-MPSCs). Our findings reveal that EPS can not only utilize its uncoordinated Pb2+ coordination through the large π bond of the benzene ring, but also the functional groups of C=O and C≡N in its additives, benzophenone peroxide and azobisisobutyronitrile, respectively, play an efficient role in passivating lead defects. Furthermore, EPS effectively acts as a moisture barrier, preventing moisture from entering the interior of the device. This significantly improves device stability and immobilizes lead ions, preventing lead leakage. Our approach not only provides an efficient and environmentally friendly method to recycle EPS, but also offers new solutions to address fundamental scientific challenges in perovskite solar cells, such as lead leakage and stability issues.

Dendritic growth lowers carbon electrode work function for efficient perovskite solar cells

A major challenge in the development of printable mesoscopic perovskite solar cells (p-MPSCs) is the modification of the carbon electrode's work function to facilitate holes extraction and transport in carbon-based hole transport layer (HTL)-free devices. To address this, we present an innovative approach: in-situ polymerization of aniline on nano-graphite's surface, followed by carbonization, forming a dendritic structure. The modified carbon electrode exhibits reduced work function from −5.06 eV to −5.19 eV and improved energy level alignment with perovskite, facilitating charge collection and significantly enhancing hole collection. This results in a photovoltaic conversion efficiency increase from 15.16 % to 18.19 % in p-MPSCs. Furthermore, the modified carbon electrode-based p-MPSCs exhibit exceptional stability, maintaining high power conversion efficiency even after 10,000-h air exposure without encapsulation. Our work presents a vital strategy for improving photovoltaic conversion characteristics and stability of p-MPSCs through carbon electrode interface modification.

Competitive Formation Mechanism for Bidentate Passivation of Halogen Vacancies in Perovskite Based on 6-Chloropurine.

For metal halide perovskite solar cells, bidentate passivation (BP) is highly effective, but currently, only passivation sites rather than molecular environments are being considered. Here, the authors report an effective approach for high-performance fully printable mesoscopic perovskite solar cells (FP-PSCs) through the BP strategy using the multidentate molecule 6-chloropurine (6-CP). By utilizing density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) characterizations, the competition mechanism is identified of BP between the chlorine atom and neighboring nitrogen atom of the imidazole and pyrimidine rings. Through BP between the chlorine atom and adjacent nitrogen atom in imidazole, the power conversion efficiency (PCE) of the pristine samples is significantly enhanced from 16.25% to 17.63% with 6-CP. The formation of BP enhances interfacial hole selectivity and charge transfer, and suppresses nonradiative recombination, improving device stability under high humidity conditions. The competition mechanism of BP between two aromatic cycles provides a path for designing molecular passivants and selecting passivation pathways to approach theoretical limits.

Two-in-one additive engineering strategy induced high-quality CsPbBr3 film in printable mesoscopic perovskite solar cells

The use of all-inorganic cesium lead tribromide (CsPbBr3) in photovoltaics has gained significant attention due to its outstanding environmental stability and low cost of preparation. Printable perovskite solar cells (PSCs) based on CsPbBr3 have demonstrated a more straightforward fabrication procedure and remarkable stability, indicating great development potential. However, the preparation of the CsPbBr3 film can be challenging, as it requires depositing a high-quality PbBr2 film in a triple-layer porous scaffold and avoiding the incomplete conversion of PbBr2 in the subsequent step. Herein, we propose a two-in-one additive engineering strategy using 4-tert-Butylpyridine (TBP) into the PbBr2 solution and dimethyl sulfoxide (DMSO) to the CsBr precursor. The improved perovskite layer with better infiltration in scaffold, low carrier recombination rate and high absorption ability results in the boosting performance of PSCs. When the TBP is coupled with DMSO to fabricate printable mesoscopic CsPbBr3 PSCs, the device achieves a power conversion efficiency as high as 8.36 %. Furthemore, the modified CsPbBr3 PSC without any encapsulation retains above 97 % of its initial efficiency after 1600 h of storage in ambient air, indicating outstanding stability.