Continuous Maximum Power Point Tracking Research Articles

Tuning Isomerism Effect in Organic Bulk Additives Enables Efficient and Stable Perovskite Solar Cells

Organic additives with multiple functional groups have shown great promise in improving the performance and stability of perovskite solar cells. The functional groups can passivate undercoordinated ions to reduce nonradiative recombination losses. However, how these groups synergistically affect the enhancement beyond passivation is still unclear. Specifically, isomeric molecules with different substitution patterns or molecular shapes remain elusive in designing new organic additives. Here, we report two isomeric carbazolyl bisphosphonate additives, 2,7-CzBP and 3,6-CzBP. The isomerism effect on passivation and charge transport process was studied. The two molecules have similar passivation effects through multiple interactions, e.g., P = O···Pb, P = O···H-N and N-H···I. 2,7-CzBP can further bridge the perovskite crystallites to facilitates charge transport. Power conversion efficiencies (PCEs) of 25.88% and 21.04% were achieved for 0.09 cm2 devices and 14 cm2 modules after 2,7-CzBP treatment, respectively. The devices exhibited enhanced operational stability maintaining 95% of initial PCE after 1000h of continuous maximum power point tracking. This study of isomerism effect hints at the importance of tuning substitution positions and molecular shapes for organic additives, which paves the way for innovation of next-generation multifunctional aromatic additives.

25.91%-Efficiency and Durable Inverted Perovskite Solar Cells Enabled by a Multifunctional Molecule Mediated Precursor Engineering.

The stability of the precursor is essential for producing high-quality perovskite films with minimal non-radiative recombination. In this study, methionine sulfoxide (MTSO), which features multiple electron-donation sites, is strategically chosen as a precursor stabilizer and crystal growth mediator for inverted perovskite solar cells (PSCs). MTSO stabilizes the precursor by inhibiting the oxidation of iodide ions and passivates charged traps through coordination and hydrogen bonding interactions. This leads to enhanced crystallinity, reduced non-radiative recombination, and decreased internal residual stress in perovskite film. As a result, remarkable power conversion efficiencies of 25.91% (certified 25.76%) with a minimal voltage deficit of 0.36V for a 0.09-cm2 inverted PSC, and 21.96% for a 12.96-cm2 (active area) perovskite minimodule, have been achieved, respectively. Furthermore, the unencapsulated devices demonstrated excellent long-term thermal aging and operational stability, retaining over 90% and 92% of their original efficiencies after 500h of continuous thermal aging at 85°C and 2500h of continuous maximum power point tracking under 1 sun (white light LED array) illumination at 30±5°C. This study underscores the importance of the rational design of functional molecules for stabilizing the precursor and regulating the crystallization of perovskite films, advancing the practical development of PSCs.

Stereo-Hindrance Induced Conformal Self-Assembled Monolayer for High Efficiency Inverted Perovskite Solar Cells.

Self-assembled monolayers (SAMs) are employed as hole-selective contacts in inverted perovskite solar cells (PSCs) and have achieved record power conversion efficiency (PCE) over 26%. However, the tendency of extensively employed SAM [2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid to aggregate leads to its uneven coverage to the transparent conducting oxide substrate, which subsequently compromises the photovoltaic performance. Herein, a novel tert-butyl functionalized phosphonic acid carbazole SAM is developed, i.e., (4-(3,6-di-tert-butyl-9H-carbazol-9-yl)butyl)phosphonic acid (tBu-4PACz), and introduced to a mixed SAM system as the hole-extraction layer in inverted PSCs. The stereo-hindrance of the bulky tert-butyl group prevents undesired aggregation and leads to better conformality, which facilitates more efficient hole-extraction and suppresses interfacial recombination losses. The tBu-4PACz SAM-based inverted PSC has achieved record level PCE of 26.25% (26.21%, certificated) with outstanding fill factors over 86%. Moreover, the mixed SAM based inverted PSC devices maintained over 94.7% of their initial efficiency after 500h continuous maximum power-point tracking under simulation 1-sun irradiation.

Iodide Management and Oriented Crystallization Modulation for High-Performance All-Air Processed Perovskite Solar Cells.

Halide-related defects at the buried interface not only cause nonradiative recombination, but also seriously impair the long-term stability of perovskite solar cells (PSCs). Herein, a bottom-up, all-in-one modification strategy is proposed by introducing a multisite antioxidant ergothioneine (EGT) at the buried interface to manage iodide ions and manipulate crystallization dynamics. The findings demonstrate that EGT not only passivates uncoordinated Sn4+/Pb2+ defects, but also firmly anchors iodide ions and inhibits their oxidation to I2. Additionally, the modification by EGT enhances the oriented crystallization of perovskite, improves the carrier dynamics, and releases residual stresses. Consequently, the optimized all-air processed device (Rb0.02(FA0.95Cs0.05)0.98PbI2.91Br0.03Cl0.06) achieves a remarkable power conversion efficiency (PCE) of 25.13%, which is among the highest values reported for devices fabricated in air, along with ultrahigh open-circuit voltage (VOC) of 1.191V and fill factor (FF) of 84.9%. The optimized device without encapsulation exhibits strong humidity, thermal, and operational stability under ISOS protocol. Specifically, the initial efficiency of the device is retained at 90.12% after 1512 h of thermal ageing at 65°C and 90.14% after 930 h of continuous maximum power point tracking (MPPT) under simulated AM1.5 illumination.

Alkyl Chains Tune Molecular Orientations to Enable Dual Passivation in Inverted Perovskite Solar Cells.

Nonradiative recombination losses occurring at the interface pose a significant obstacle to achieve high-efficiency perovskite solar cells (PSCs), particularly in inverted PSCs. Passivating surface defects using molecules with different functional groups represents one of the key strategies for enhancing PSCs efficiency. However, a lack of insight into the passivation orientation of molecules on the surface is a challenge for rational molecular design. In this study, aminothiol hydrochlorides with different alkyl chains but identical electron-donating (-SH) and electron-withdrawing (-NH3 +) groups were employed to investigate the interplay between molecular structure, orientation, and interaction on perovskite surface. The 2-Aminoethane-1-thiol hydrochloride with shorter alkyl chains exhibited a preference of parallel orientations, which facilitating stronger interactions with the surface defects through strong coordination and hydrogen bonding. The resultant perovskite films following defect passivation demonstrate reduced ion migration, inhibition of nonradiative recombination, and more n-type characteristics for efficient electron transfer. Consequently, an impressive power conversion efficiency of 25 % was achieved, maintaining 95 % of its initial efficiency after 500 hours of continuous maximum power point tracking.

Alkyl Chains Tune Molecular Orientations to Enable Dual Passivation in Inverted Perovskite Solar Cells

AbstractNonradiative recombination losses occurring at the interface pose a significant obstacle to achieve high‐efficiency perovskite solar cells (PSCs), particularly in inverted PSCs. Passivating surface defects using molecules with different functional groups represents one of the key strategies for enhancing PSCs efficiency. However, a lack of insight into the passivation orientation of molecules on the surface is a challenge for rational molecular design. In this study, aminothiol hydrochlorides with different alkyl chains but identical electron‐donating (−SH) and electron‐withdrawing (−NH3+) groups were employed to investigate the interplay between molecular structure, orientation, and interaction on perovskite surface. The 2‐Aminoethane‐1‐thiol hydrochloride with shorter alkyl chains exhibited a preference of parallel orientations, which facilitating stronger interactions with the surface defects through strong coordination and hydrogen bonding. The resultant perovskite films following defect passivation demonstrate reduced ion migration, inhibition of nonradiative recombination, and more n‐type characteristics for efficient electron transfer. Consequently, an impressive power conversion efficiency of 25 % was achieved, maintaining 95 % of its initial efficiency after 500 hours of continuous maximum power point tracking.

Silver coordination-induced n-doping of PCBM for stable and efficient inverted perovskite solar cells

The bidirectional migration of halides and silver causes irreversible chemical corrosion to the electrodes and perovskite layer, affecting long-term operation stability of perovskite solar cells. Here we propose a silver coordination-induced n-doping of [6,6]-phenyl-C61-butyric acid methyl ester strategy to safeguard Ag electrode against corrosion and impede the migration of iodine within the PSCs. Meanwhile, the coordination between DCBP and silver induces n-doping in the PCBM layer, accelerating electron extraction from the perovskite layer. The resultant PSCs demonstrate an efficiency of 26.03% (certified 25.51%) with a minimal non-radiative voltage loss of 126 mV. The PCE of resulting devices retain 95% of their initial value after 2500 h of continuous maximum power point tracking under one-sun irradiation, and > 90% of their initial value even after 1500 h of accelerated aging at 85 °C and 85% relative humidity.

Fabricating Solid‐Solution‐Type Perovskite/Fluoride Nanocomposites Through Sublattice Interlocking for High‐Performance Photovoltaics

AbstractAll‐inorganic α‐phase CsPbI3 perovskite with a suitable bandgap and superb optoelectronic properties is transforming the landscape of perovskite photovoltaics, but its long‐term lability associated with “soft” ionic lattice still imposes a great challenge for practical applications. Herein, a unique solid‐solution fluorination strategy is proposed to deliver an “ideal” perovskite matrix of α‐phase CsPbI3 abundant with F ions through interlocking the soft lattice of CsPbI3 with cubic‐phase CsF·3/2HF. Such a sublattice interlocking can not only stabilize the soft lattice of α‐phase CsPbI3 perovskite nanocrystals but also passivate their notorious surface defects, thereby producing a “rigid” solid‐solution‐type perovskite/fluoride CsPbI3/CsF (termed as CsPbI3:F) nanocomposite with excellent long‐term stability and a near‐unity photoluminescence efficiency. Of particular note is that these CsPbI3:F nanocomposites can work well as effective grain boundary anchors to significantly improve the photovoltaic performance of perovskite solar cells because of their F‐rich perovskite lattice, achieving a T80 stability of 1500 h under continuous maximum power point tracking and AM 1.5G illumination without the need for encapsulation. This work paves a new way to deliver perovskite materials with desirable properties for photovoltaics.

Functional-Group-Induced Single Quantum Well Dion-Jacobson 2D Perovskite for Efficient and Stable Inverted Perovskite Solar Cells.

In two-dimensional/three-dimensional (2D/3D) perovskite heterostructure, randomly distributed multiple quantum wells (QW) 2D perovskites are frequently generated, which are detrimental to carrier transport and structural stability. Here, the high quality 2D/3D perovskite heterostructure is constructed by fabricating functional-group-induced single QW Dion-Jacobson (DJ) 2D perovskites. The utilization of ─OCH3 in the precursor solution facilitates the formation of colloidal particles with uniform size, resulting in the production of a pure 2D DJ perovskite with an n value of 3. This strategy facilitates the improvement of 3D structural stability and expedites carrier transport. The resultant devices accomplish a power conversion efficiency of 25.26% (certified 25.04%) and 23.56% at a larger area (1 cm2 ) with negligible hysteresis. The devices maintain >96% and >89% of their initial efficiency after continuous maximum power point tracking under simulated AM1.5 illumination for 1300h and under damp-heat conditions (85°C and 85% RH) for 1010h, respectively.

Rationally Tailoring Chiral Molecules to Minimize Interfacial Energy Loss Enables Efficient and Stable Perovskite Solar Cells Using Vacuum Flash Technology.

Facing the defects and energy barrier at the interface of perovskite solar cells, we propose a chiral molecule engineering strategy to simultaneously heal interfacial defects and regulate interfacial energy band alignment. S-ibuprofen (S-IBU), R-ibuprofen (R-IBU), and racemic ibuprofen (rac-IBU) are used to post-treat perovskite films. rac-IBU molecules possess the strongest anchoring on the surface of perovskites among all chiral molecules, translating into the best defect passivation effect. The hydrophobic isobutyl group and benzene ring could increase the film moisture resistance ability. Due to reduced interfacial defects and interfacial energy barrier, rac-IBU enables efficient devices with a maximum efficiency exceeding 24% based on vacuum flash technology without antisolvents. The encapsulated rac-IBU-modified device could maintain 90% of its initial performance after 1040 h of continuous maximum power point tracking. This work provides a feasible route to minimize interfacial nonradiative recombination losses by controlling spatial conformation via rational chiral molecule engineering.

Engineering Amorphous-Crystallized Interface of ZrNx Barriers for Stable Inverted Perovskite Solar Cells.

It is challenging to achieve long-term stability of perovskite solar cells due to the corrosion and diffusion of metal electrodes. Integration of compact barriers into devices has been recognized as an effective strategy to protect the perovskite absorber and electrode. However, the difficulty is to construct a thin layer of a few nanometers that can delay ion migration and impede chemical reactions simultaneously, in which the delicate microstructure design of a stable material plays an important role. Herein, ZrNx barrier films with high amorphization are introduced in p-i-nperovskite solar cells. To quantify the amorphous-crystalline (a-c) density, pattern recognition techniques are employed. It is found the decreasing a-c interface in an amorphous film leads to dense atom arrangement and uniform distribution of chemical potential, which retards the interdiffusion at the interface between ions and metal atoms and protect the electrodes from corrosion. The resultant solar cells exhibit improved operational stability, which retains 88% of initial efficiency after continuous maximum power point tracking under 1-Sun illumination at room temperature (25 °C) for 1500 h.

Multifunctional Ionic Liquid as an Interfacial Modifier for High-Performance and Stable NiOx-Based Inverted Perovskite Solar Cells.

Interface instability has evolved into the primary aspect that limits the durability improvement of perovskite solar cells (PSCs). Interface modification with suitable molecules is widely considered an effective path for improving the interface state. Herein, an ionic liquid modified layer, 1-ethyl-3-methylimidazolium aminoacetate (EMIMAE), is brought to modify NiOx/perovskite interface. The EMIMAE layer can interact with the adjacent layer to regulate the perovskite growth, passivate defects in the film, and promote charge transport in PSCs. Eventually, the optimized device's efficiency rises to 18.6%, which is a substantial improvement over the control device. Particularly, after 1000 h of continuous maximum power point tracking, the device can still retain 95% of its initial efficiency. This work proposes a simple idea to ameliorate the device interface and boost the commercialization of NiOx based devices.

Hydrogen bonding drives the self-assembling of carbazole-based hole-transport material for enhanced efficiency and stability of perovskite solar cells

Designing a hole-transport material (HTM) that guarantees effective hole transport while self-assembling at the perovskite|HTM interface with the formation of an ordered interlayer, has recently emerged as a promising strategy for high-performance and stable perovskite solar cells (PSCs). Hydrogen bonding (HB) is a versatile multi-functional tool for the design of small molecular HTMs. However, to date, its employment is mostly limited to p-i-n inverted PSCs. This study demonstrates the advantages of a novel HTM design that can self-assemble into a long-range ordered interlayer on the perovskite surface via HB association. A hydro-functional HTM (O1) is compared to a reference HTM (O2) that cannot form HB due to the replacement of the amide group of O1 with a plain butyl alkyl chain in O2. As a result, O1-based n-i-p PSCs display enhanced hole extraction reaction, suppressed interfacial charge recombination, reduced hysteresis effect, and an increase in Voc (by 60 mV), FF (>11% increase), and overall power conversion efficiency, PCE (32% increase) compared to the case of HB-free O2-based devices. Remarkable stability is observed for unencapsulated O1 cells, with a T80 lifetime of 35.5 h under continuous maximum power point tracking in air. This work emphasizes the role of HB-directed self-assembling in simultaneously enhancing both the PCE and stability of popular n-i-p PSCs. This study paves the way for the development of new hydro-functional charge-transport material designs for efficient and stable PSCs.

Molecular Hinges Stabilize Formamidinium‐Based Perovskite Solar Cells with Compressive Strain

AbstractFormamidinium (FA)‐based lead triiodide have emerged as promising light‐harvesting materials for solar cells due to their intriguing optoelectronic properties. However, obstacles to commercialization remain regarding the primary intrinsic materials instability, wherein volatile organic components of FA+ cations are prone to escape under operational stressors. Herein, stabilizing FA‐based perovskite through toughening the interface with the symmetric molecule of 1,1′‐(Methylenedi‐4,1‐phenylene) bismaleimide (BMI) is reported. BMI with two maleimides can simultaneously bind with FA+ and/or undercoordinated Pb2+ through chemical bonding, which also compresses the resultant perovskite lattice. The chemical bonding and strain modulation synergistically not only passivate film defects, but also inhibit perovskite decomposition, thus significantly improving the intrinsic stability of perovskite films. As a result, the BMI‐modified perovskite solar cells (PSCs) show improved power conversion efficiency (PCE) from 21.4% to 22.7% and enhanced long‐term operational stability, maintaining 91.8% of the initial efficiency after 1000 h under continuous maximum power point tracking. The findings shed light on the synergetic effects of chemical interactions and physical regulations, which opens a new avenue for stable and efficient perovskite‐based optoelectronic devices.

Towards effective energy harvesting from stacks of soil microbial fuel cells

The 2050 net-zero carbon target can only be achieved with renewable energy solutions that can drastically reduce carbon emissions. Soil microbial fuel cells (SMFCs) have significant potential as a low-cost and carbon-neutral energy conversion technology. Finding the most practical and energy efficient strategy to operate SMFCs is crucial for transitioning this technology from the lab to field implementations. In this study, an innovative self-sustaining and model-based energy harvesting strategy was developed and tested for the first time on SMFC stacks. The model, based on a first-order equivalent electrical circuit (EEC), enables real-time and continuous maximum power point tracking, without the need for offline analysis of electrochemical parameters. Power extraction from the SMFCs to fully charge a 3.6 V NiMH battery, was carried out for 24 h: the longest test duration reported so far on biological fuel cells for such energy harvesting strategy. A novel second-order EEC was also proposed to better describe the electrical dynamics of the SMFC. Our results provide important advances on both accurate model-based electrochemical parameter identification techniques and maximum power point tracking algorithms, for optimal energy extraction from SMFCs. Consequently, this study paves the way for successful implementations of SMFCs towards viable green energy solutions. • Self-sustaining, model-based energy harvesting strategy for SMFC stacks. • Tailored equivalent electrical circuit for real-time maximum power point tracking. • Performance demonstrated over continuous operation.

Novel Phenothiazine‐Based Self‐Assembled Monolayer as a Hole Selective Contact for Highly Efficient and Stable p‐i‐n Perovskite Solar Cells

AbstractRecent advances in perovskite solar cells (PSCs) performance have been closely related to improved interfacial engineering and charge selective contacts. Here, a novel and cost‐competitive phenothiazine based, self‐assembled monolayer (SAM) as a hole‐selective contact for p‐i‐n PSCs is introduced. The molecularly tailored SAM enables an energetically well‐aligned interface with the perovskite absorber, with minimized nonradiative interfacial recombination loss, thus dramatically improving charge extraction/transport and device performance. The resulting PSCs exhibit a power conversion efficiency (PCE) of up to 22.44% (certified 21.81%) with an average fill factor close to 81%, which is among the highest efficiencies reported to date for p‐i‐n PSCs. The new SAM also demonstrates the outstanding operational stability of the PSC, with increasing PCE from 20.3% to 21.8% during continuous maximum power point tracking under a simulated 1 sun illumination for 100 h. The reported findings highlight the great potential of engineered SAMs for the fabrication of stable and high performing PSCs.

Interfacial toughening with self-assembled monolayers enhances perovskite solar cell reliability.

Iodine-terminated self-assembled monolayer (I-SAM) was used in perovskite solar cells (PSCs) to achieve a 50% increase of adhesion toughness at the interface between the electron transport layer (ETL) and the halide perovskite thin film to enhance mechanical reliability. Treatment with I-SAM also increased the power conversion efficiency from 20.2% to 21.4%, reduced hysteresis, and improved operational stability with a projected T80 (time to 80% initial efficiency retained) increasing from ~700 hours to 4000 hours under 1-sun illumination and with continuous maximum power point tracking. Operational stability-tested PSC without SAMs revealed extensive irreversible morphological degradation at the ETL/perovskite interface, including voids formation and delamination, whereas PSCs with I-SAM exhibited minimal damage accumulation. This difference was attributed to a combination of a decrease in hydroxyl groups at the interface and the higher interfacial toughness.

Tougher solar cell interfaces

Solar Cells The low formation energies of the active layers in perovskite solar cells lead to low-toughness materials that are compliant and soft, which limits their interface stability and long-term reliability. Dai et al. show that treatment with iodine-terminated self-assembled monolayers that react with surface hydroxyl groups (which ultimately creates unwanted charge traps and voids) leads to a 50% increase of adhesion toughness between the electron transport layer and a mixed-composition perovskite thin film. The projected point at which 80% of the operating efficiency in perovskite solar cells was still retained increased from ∼700 to 4000 hours for 1-sun exposure with continuous maximum power point tracking. Science , this issue p. [618][1] [1]: /lookup/doi/10.1126/science.abf5602

Chemical anti-corrosion strategy for stable inverted perovskite solar cells.

One big challenge for long-lived inverted perovskite solar cells (PSCs) is that commonly used metal electrodes react with perovskite layer, inducing electrode corrosion and device degradation. Motivated by the idea of metal anticorrosion, here, we propose a chemical anticorrosion strategy to fabricate stable inverted PSCs through introducing a typical organic corrosion inhibitor of benzotriazole (BTA) before Cu electrode deposition. BTA molecules chemically coordinate to the Cu electrode and form an insoluble and polymeric film of [BTA-Cu], suppressing the electrochemical corrosion and reaction between perovskite and the Cu electrode. PSCs with BTA/Cu show excellent air stability, retaining 92.8 ± 1.9% of initial efficiency after aging for 2500 hours. In addition, >90% of initial efficiency is retained after 85°C aging for over 1000 hours. PSCs with BTA/Cu also exhibit good operational stability, and 88.6 ± 2.6% of initial efficiency is retained after continuous maximum power point tracking for 1000 hours.

Rising from the Ashes: Gaseous Therapy for Robust and Large-Area Perovskite Solar Cells

Scalable fabrication of perovskite solar cells (PSCs) with high reliability is one of the most pivotal concerns that must be addressed before they get into the photovoltaic (PV) market. Scaling large-area high-quality perovskite films is of great importance in this process. Here, gaseous therapy has been proposed for the post-treatment of perovskite films with high scalability and low cost. An inspiring evolvement from poor perovskite films to high quality ones is demonstrated under a joint treatment of methylamine gas and hot solvent vapors. The perovskite films are completely reconstructed and repaired regardless of the morphology of the original films. As a consequence, small-area (0.09 cm2) and large-area (4 cm2) PSCs based on the healed MAPbI3 films can afford J-V scanned efficiencies of 19.2 and 16.5% under a reverse sweep, respectively. Furthermore, stabilized power outputs of 18.5 and 15.2% are obtained from the small one and large one under continuous maximum power point tracking.