Improved Device Stability Research Articles

Surface Template Realizing Oriented Perovskites for Highly Efficient Solar Cells.

Formamidinium lead iodide (FAPbI3) perovskite films, ensuring optically active phase purity with uniform crystal orientation, are ideal for photovoltaic applications. However, the optically active α-FAPbI3 phase is easy to degrade into δ-phase due to numerous defects within randomly oriented films. Here, a "quasi-2D" perovskite template is pre-deposited on the film surface within the crystallization process based on the two-step preparation technology, which directly induced pure and highly orientated crystallization of α-FAPbI3 across the downward growth process. Furthermore, the enlarged interaction between 2D components with colloidal properties and lead iodide delayed the crystallization process effectively, yielding high crystallinity with low trap state density. The resulting perovskite photovoltaic devices exhibited a champion efficiency as high as 25.79% with comprehensively improved device stability. This work provides new insights into the utilization of 2D components and the formation mechanism behind 2D perovskites.

A dendritic hexamer acceptor enables 19.4% efficiency with exceptional stability in organic solar cells

To achieve the commercialization of organic solar cells (OSCs), it is crucial not only to enhance power conversion efficiency (PCE) but also to improve device stability through rational molecular design. Recently emerging giant molecular acceptor (GMA) materials offer various advantages, such as precise chemical structure, high molecular weight (beneficial to film stability under several external stress), and impressive device efficiency, making them a promising candidate. Here, we report a dendritic hexamer acceptor developed through a branch-connecting strategy, which overcomes the molecular weight bottleneck of GMAs and achieves a high production yield over 58%. The dendritic acceptor Six-IC exhibits modulated crystallinity and miscibility with the donor, thus better morphology performance compared to its monomer, DTC8. Its charge transport ability is further enhanced by additional channels between the armed units. Consequently, the binary OSCs based on D18:Six-IC achieves a cutting-edge efficiency of 19.4% for high-molecular weight acceptor based systems, as well as decent device stability and film ductility. This work reports high-performance OSCs based on dendritic molecule acceptor with a molecular weight exceeding 10000 g/mol and shares the understanding for designing comprehensively high-performing acceptor materials.

Construction of Linear Tetramer-Type Acceptors for High-Efficiency and High-Stability Organic Solar Cells.

Thanks to the development of non-fullerene acceptor (NFA) materials, the photovoltaic conversion efficiency (PCE) of organic solar cells (OSCs) has exceeded 20 %, which has met the requirements for commercialisation. In the current stage, the main focus is to balance the performance and stability. It has been shown that all-polymer formulation can improve device stability, however, PCE is not in satifsfaction, and the batch-to-batch variation leads to quality control issues. In this work, we constructed monodispersed tetramer NFA materials named G-1 and G-2, to best integrate the merits of small molecule and polymer. Density functional theory (DFT) calculations and experimental results showed that different connecting units at the centre could significantly affect the molecular planarity and thin film morphology. The alkene-bonded tetramer G-1 had a more regioregular structure, which leads to better molecular planarity, and more ordered packing in thin film. More importantly, the oligomeration induced a favourable face-on orientation, achieved a lower binding energy and exhibited a higher photoluminescence yield. As a result, the exciton and charge carrier kinetics was optimized with reduced non-radiative energy loss. The OSC based on PM6 : G-1 achieved a PCE of 19.6 %, which is the highest PCE reported so far for oligomer-based binary OSC. In addition, the device stability was largely improved, showing a lifetime over 10000 hours in the inverted OSC device.

Narrowband emission and enhanced stability in top-emitting OLEDs with dual resonant cavities.

Capping layers (CPLs) are commonly employed in top-emitting organic light-emitting diodes (TEOLEDs) due to their ability to optimize color purity, enhance external light out-coupling efficiency, and improve device stability. However, the mismatch in refractive index between CPLs and thin film encapsulation (TFE) often induces light trapping. This study introduces a novel approach by combining a low refractive index material, lithium fluoride (LiF), with the traditional TFE material, silicon nitride (SiNx), to form a combined CPL (LiF/SiNx), resulting in improved light outcoupling and light reflection properties. The significant refractive index contrast between LiF and SiNx can facilitate enhanced light extraction by redirecting internally reflected light through evanescent waves. Moreover, the LiF/SiNx CPLs function as a secondary resonant cavity, leading to reduced emission spectral bandwidth and enhanced light extraction compared to the control TEOLEDs that only incorporate the primary cavity of organic active layers. As a result, incorporating the LiF/SiNx CPLs significantly increases current efficiency from 125.0 cd A-1 to 163.6 cd A-1 for green devices, from 71.2 cd A-1 to 110.1 cd A-1 for red devices, and from 43.1 cd A-1 to 53.1 cd A-1 for blue devices, with the corresponding full width at half maximum decreased from 20 nm to 10 nm, 26 nm to 14 nm, and 21 nm to 12 nm, respectively, demonstrating the compatibility of the CPLs with different color devices. Notably, an LT95 lifetime of 51 300 hours for green devices was achieved when tested at 1000 cd m-2. Utilizing narrow-band light emission without spectral overlap of each color enables the generation of purer and more vivid colors for display.

Ameliorating Defects in Wide Bandgap Tin Perovskite Solar Cells Using Fluorinated Solvent and Hydrazide.

Surface passivation with multifunctional molecules is an effective strategy to mitigate the defect and improve the performance and stability of perovskite solar cells (PSCs). Here, the fabrication of awide bandgap-PSC is reported with tin perovskite (WB-Sn-HP; bandgap: 1.68 eV), followed by molecular surface passivation using 4-Fluoro-benzohydrazide (F-BHZ). WB-Sn-PSC has demonstrated a promising device efficiency of 11.14% with improved device stability. The key to enhancing device performance lies in the meticulous engineering of both surface and bulk properties of WB-Sn-HP film with F-BHZ treatment as a consequence of stronger electrostatic potential and molecular interaction with hydrazine and carbonyl functionalities. A compact perovskite film and highly crystalline film growth results in a longer carrier lifetime and surface defect mitigation with the control of Sn2+ oxidation as supported by theoretical calculations. This work underlines the promising potential of chemical engineering to improve the device performance of WB-Sn-PSC and stabilityusing multifunctional passivating molecules.

Assessing degradation in perovskite solar cells via thermal hysteresis of photocurrent and device simulation

Understanding the degradation mechanisms of perovskite solar cell (PSC) is paramount to addressing stability-related issues. Photocurrent loss is widely observed in the degraded PSC. Here, we investigate the degradation of PSC by probing the thermal hysteresis of photocurrent (THPC) and the dynamics of thermally active ionic or recombination processes. Degraded devices exhibit a considerably higher degree of variation in the photogenerated current, encompassing a broad spectrum of photo-induced ionic charge accumulation. THPC reveals changes driven by the accumulation of interfacial ionic charges and active defects under photo-thermal drifting, as supported by capacitance analysis. Device simulation corroborates that the interfacial surface defect formed at the interfacial layer in the device structure wields a substantial influence on device degradation, particularly in cases of photocurrent loss. This study underscores the direct correlation between the degradation of PSC and the presence of thermally activated traps and interfacial charge accumulation emphasizing the importance of passivating these pathways to improve device stability.

(Invited) Towards Outdoor Operation of Perovskite Solar Cells

Organic-inorganic hybrid halide perovskites represent a new class of light absorbers that have demonstrated multiple ideal characteristics and a rapid performance progress for solar conversion applications. Perovskite-based photovoltaic (PV) technologies have attracted significant R&D attention in the PV community as a promising next-generation approach for future PV applications. The certified efficiency of single-junction perovskite solar cells (PSCs) has reached greater than 26%. In order to reach the commercialization stage for perovskite PV, significant efforts are still needed to demonstrate the robust operation under real-world condition for multiple decades. To speed up this process, it is important to develop accelerated aging test protocols and understand their correlation to device operation under outdoor conditions. Here, I will first present our recent studies on perovskite surface engineering to improve device stability under indoor operational conditions. Using molecules/structures based on bulky organic cations (e.g., phenethylammonium) to improve the surface or interface properties is promising for improving PSC performance. A few strategies on suppressing defect formation, improving bulk and surface morphology, and reducing transport barriers for better extraction will be highlighted. In the second part of presentation, I will discuss our recent progress toward understanding the correlation between indoor and outdoor PSC degradation behaviours. Understanding device reliability under real-world outdoor conditions where multiple stress factors (e.g., light, heat, humidity) coexist is critical to moving perovskite PV toward commercialization. It is important to understand the link between indoor and outdoor behaviors in order to help identify accelerated indoor testing protocols to quickly guide PSC development.

Oxidation effects on the optical and electrical properties of MoS2 under controlled baking temperatures

As silicon-based semiconductor technology scales down to the nanoscale, it encounters significant physical limitations, including reduced electron mobility, short-channel effects, and increased heat generation, which hinder device performance and reliability. Two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), offer great potential with superior electrical properties at the nanoscale, but the issue of excessive heat generation in highly integrated circuits persists. Therefore, it is essential to investigate the thermal durability of MoS2 under various heating conditions and its impact on physical properties and device performance. In this study, we systematically investigated the oxidation behavior and related physical property variations of CVD-grown MoS2 monolayers by baking them at different temperatures. It was clearly revealed that high-temperature baking induces p-doping and structural deformation, significantly altering optical and electrical properties. Despite the degradation in device performance, reduced interfacial Coulomb scattering was observed, suggesting potential for improved device stability. This study underscores the importance of understanding thermal stability to accelerate the development of 2D semiconductors for next-generation electronic devices.

Solution-Processable Metal-Oxide Thin-Film Transistors with Radiation Resistance

The impact of 5 MeV high-energy proton irradiation on solution-processed metal-oxide thin-film transistors (TFTs) has been studied. TFTs based on zinc oxide (ZnO) and indium gallium zinc oxide (a-IGZO) showed a substantial negative shift in threshold voltage values (ΔVth ≤ −30 V) or transitioned to a conductor state as the proton radiation dose increased. This effect is attributed to the formation of proton irradiation-induced oxygen vacancies in the metal-oxide semiconductor layer. Conversely, zinc tin oxide (ZTO) devices with an optimized composition demonstrated good stability due to the strong oxygen binding characteristics of tin atoms. Additionally, back-channel passivation of oxide semiconductor TFTs with an n-type organic semiconductor layer significantly improved device stability. Our research indicates that solution-processed metal oxide semiconductors hold significant promise as radiation-resistant large-area electronic devices for nuclear and aerospace applications.

Micro-homogeneity of lateral energy landscapes governs the performance in perovskite solar cells

Suppression of energy disorders in the vertical direction of a photovoltaic device, along which charge carriers are forced to travel, has been extensively studied to reduce unproductive charge recombination and thus achieve high-efficiency perovskite solar cells. In contrast, energy disorders in the lateral direction of the junction for large-area modules are largely overlooked. Herein, we show that the micro-inhomogeneity characteristics in the surface lateral energetics of formamidinium (FA)-based perovskite films also significantly influence the device performance, particularly with accounting for the stability and scale-up aspects of the devices. By using organic amidinium passivators, instead of the most commonly used organic ammonium ones, the micro-inhomogeneity in the lateral energy landscapes can be suppressed, greatly improving device stability and efficiency of FA-based single-junction perovskite solar cells.

Recrystallizing Sputtered NiOx for Improved Hole Extraction in Perovskite/Silicon Tandem Solar Cells

AbstractSputtering nickel oxide (NiOx) is a production‐line‐compatible route for depositing hole transport layers (HTL) in perovskite/silicon tandem solar cells. However, this technique often results in films with low crystallinity and structural flaws, which can impair electronic conductivity. Additionally, the complex surface chemistry and inadequate Ni3+/Ni2+ ratio impede the effective binding of self‐assembled monolayers (SAMs), affecting hole extraction at the perovskite/HTL interface. Herein, these issues are addressed using a recrystallization strategy by treating sputtered NiOx thin films with sodium periodate (NaIO4), an industrially available oxidant. This treatment improved crystallinity and increased the Ni3+/Ni2+ ratio, resulting in a higher content of nickel oxyhydroxide. These enhancements strengthened the SAM's anchoring capability on NiOx and improved the hole extraction at the perovskite/HTL interface. Moreover, the NaIO4 treatment facilitated Na+ diffusion within the perovskite layer and minimized phase separation, thus improving device stability. As a result, single‐junction perovskite solar cells with a 1.68 eV bandgap achieve a power conversion efficiency (PCE) of 23.22% for an area of 0.12 cm2. Perovskite/silicon tandem cells with an area of 1 cm2 reached a PCE of 30.48%. Encapsulated tandem devices retained 95% of their initial PCE after 300 h of maximum power point tracking under 1‐sun illumination at 25 °C.

Improving Electrochemical Performance in Planar On-Chip Zn-ion Micro-Batteries via Interlayer Strategies.

The imperative development of planar on-chip micro-batteries featuring high-capacity electrodes and environmentally safer, cost-effective, and stable systems is crucial for powering forthcoming miniaturized systems-on-chip smart devices. However, research in the area of high-stability micro-batteries is limited due to the complex fabrication process, the stability of micro-electrodes during cycling, and the challenge of maintaining higher capacity within a limited device footprint. In response to this need, this study focuses on providing highly stable and high-capacity micro-electrodes. This involves adding a PEDOT layer between the electrode material and the current collector, applied within a planar polyaniline cathode and zinc anode device structure to enhance charge storage performance. This straightforward strategy not only improves device stability over long-term cycling and reduces charge transfer resistance but also increases charge storage capacities from 17.64 to 19.75 µAhcm- 2 at 0.1 mAcm- 2. Consequently, the Zn-ion micro-batteries achievenotable peak areal energy and power of 18.82 µWhcm- 2 and 4.37 mWcm- 2, respectively. This work proposes an effective strategy to enhance the electrochemical performance of planar micro-batteries, a critical advancement for the development of advanced portable electronics.

Highly Stable and Efficient N‐I‐P Structured Tin‐Rich Lead‐Tin Halide Perovskite Solar Cells with Blended Hole‐Transporting Materials

AbstractMixed lead‐tinv halide (LTH) perovskite solar cells (LTH‐PSCs) can reduce the toxicity concerns of full lead‐based PSCs and potentially optimize the bandgap to maximize efficiency. However, commonly used hole‐transporting material (HTM) 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)9,9′‐spirobifluorene (Spiro‐OMeTAD) with additional dopants Li‐bis(trifluoromethanesulfonyl) imide (Li‐TFSI) and 4‐tert‐butylpyridine (t‐BP) deteriorate oxidation Sn2+ to Sn4+ leading to trap formation. Here, the study introduces a novelty Sn‐friendly HTM for Sn‐rich LTH‐PSCs, combining Spiro‐OMeTAD with 4‐Isopropyl‐4′‐methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (dpi‐TPFB) as a dopant and blended with poly(3‐hexylthiophene‐2,3‐diyl) (P3HT). This blended HTM avoids the harmful effects of Li‐TFSI and t‐BP dopants and leverages the beneficial hydrophobic properties of P3HT, which predominantly resides on the surface with a face‐on orientation. This arrangement not only enhances charge transport and extraction but also improves device stability by protecting the perovskite from environmental factors. Optimizing the P3HT concentration of blended HTM achieved a PCE of 17.27%, the highest reported for n‐i‐p structured Sn‐rich mixed LTH‐PSCs. This HTM also significantly improved device stability, maintaining over 90% of the initial PCE after 3000 h of storage and 80% under maximum power point tracking (MPPT) for 550 h in the air.

Solution-processed Tb: Zr co-doped In2O3 thin film transistor and its dual effect on improving photostability

In this paper, Tb: Zr co-doped In2O3 TFTs were fabricated using an aqueous route. The dual effect of Tb: Zr co-doping on improving photostability was addressed. At a 5 mol% co-doping concentration, the ΔVth under NBIS first decreased and then increased as Tb: Zr ratio increased. The optimized co-doped sample (1: 2) showed a ΔVth of −3.22 V, compared to the undoped sample of −9.5 V and the single-doped samples (1: 0 and 0: 1) of −4.4 V and −4.15 V respectively. The defect state was evaluated using μ-PCD. The peak value and τ2 first decreased and then increased with an increase in Zr ratio, and reached their minimum values when the Tb: Zr co-doping ratio was 2: 1 and 1: 2, respectively. This suggested that co-doping can introduce more deep level states for the rapid recombination of photogenerated carriers and reduce shallow level states, leading to superior photostability of the co-doped devices. Further characterization by UV-Vis and XPS indicated that the increase in band gap and the decrease in oxygen vacancy were also contributing factors to improved device stability. These results highlight the great potential of solution-processed Tb: Zr co-doped In2O3 TFT for applications in low-cost and high-stability electronics.

Modeling and Optimization of Modified TiO2 with Aluminum and Magnesium as ETL in MAPbI3 Perovskite Solar Cells: SCAPS 1D Frameworks.

The perovskite device, incorporating a modified nanostructure of TiO2 as the electron transport layer, has been investigated to enhance its performance compared to the pure TiO2 device. Various materials undergo electrochemical doping or treatment on TiO2 to improve their photocatalytic application, thereby enhancing the current density, minimizing recombination, and improving device stability. In this study, a numerical SCAPS simulation was employed to validate experimental findings from the literature. According to the literature, this marks the first instance of doping Al3+ and Mg2+ on TiO2 due to their ionic radius comparable to that of Ti4+, at different doping concentrations. The device was modeled and simulated with the experimental parameters of bandgap, series, and shunt resistances for pure TiO2, aluminum-doped TiO2 (Al-TiO2), and magnesium-doped TiO2 (Mg-TiO2). From the validated results, the Al-TiO2 and Mg-TiO2-based devices' configurations with minimum percentage errors of 0.427 and 2.771%, respectively, were selected and simulated across nearly 90 (90) configurations to determine the optimum device model. Optimizing absorber thickness, bandgap, doping concentration, metal electrode, as well as series and shunt resistance resulted in enhanced device performance. According to the proposed model, Al-TiO2 and Mg-TiO2 configurations achieved higher power conversion efficiency values of 19.260 and 19.860%, respectively. This improvement is attributed to the reduction in recombination rates through the injection of a higher photocurrent density.

Non‐Ionic Perylene‐Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade‐Coated Organic Solar Cells

AbstractAs a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene‐diimide (PDI)‐based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI‐based CILs with satisfied film‐forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non‐conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n‐doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non‐ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade‐coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large‐area blade‐coating technique, and a PCE of 16.6 % was achieved in the 1‐cm2 OSC where a blade‐coated PPDINN was used.

Non-Ionic Perylene-Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade-Coated Organic Solar Cells.

As a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene-diimide (PDI)-based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI-based CILs with satisfied film-forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non-conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n-doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non-ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade-coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large-area blade-coating technique, and a PCE of 16.6 % was achieved in the 1-cm2 OSC where a blade-coated PPDINN was used.

A Facile Low Prevacuum Treatment to Enhance the Durability of Nonfullerene Organic Solar Cells

Herein, a straightforward vacuum‐assisted method is introduced to enhance the stability of nonfullerene organic solar cells (OSCs). The method, termed “prevacuum” involves subjecting the active layer (D18:Y6) to a low‐pressure vacuum (−1 bar) before thermal annealing at 100 °C. Compared to untreated devices, prevacuum‐treated OSCs exhibit a notable increase in power conversion efficiency from 13.71% to 14.90%. This enhancement is attributed to improved light absorption and charge extraction, as evidenced by external quantum efficiency measurements. Moreover, prevacuum treatment significantly improves device stability under operational conditions, with a 30% power loss occurring after 8.25 h compared to 4.5 h for untreated devices. This improvement is attributed to the removal of volatile components and impurities during the vacuum process, leading to a more hydrophobic and stable active layer. The study demonstrates the efficacy of prevacuum treatment as a simple and accessible method for enhancing the performance and longevity of OSCs, paving the way for their broader application in sustainable energy technologies.

The Crucial Role of Organic Ligands on 2D/3D Perovskite Solar Cells: A Comprehensive Review

AbstractThe exceptional performance and potential of 2D/3D perovskites for enhancing the efficiency and stability of perovskite solar cells (PSCs) are extensively studied. However, selecting appropriate organic ligands is critical to this process. The incorporation of suitable ligands into the 2D layer can passivate surface defects, regulate energy level alignment, and significantly improve device stability. Conversely, using unsuitable ligands not only fails to achieve the desired functions, but also negatively impacts device efficiency by hindering charge carrier transport and causing energy level mismatch issues. Therefore, exploring the selection of organic ligands based on different requirements is essential. In this review, recent studies are classified based on the chemical structure of organic ligands, analyze their application requirements, and provide suggestions for choosing optimal organic ligands to construct 2D/3D perovskites. Additionally, the feasibility and necessity of utilizing more efficient organic ligands while providing guidance for future research on 2D/3D PSCs are emphasized.

High Open-Circuit Voltage Wide-Bandgap Perovskite Solar Cell with Interface Dipole Layer.

Wide-bandgap perovskite solar cells (PSCs) with high open-circuit voltage (Voc) represent a compelling and emerging technological advancement in high-performing perovskite-based tandem solar cells. Interfacial engineering is an effective strategy to enhance Voc in PSCs by tailoring the energy level alignments between the constituent layers. Herein, n-type quinoxaline-phosphine oxide-based small molecules with strong dipole moments is designed and introduce them as effective cathode interfacial layers. Their strong dipole effect leads to appropriate energy level alignment by tuning the work function of the Ag electrode to form an ohmic contact and enhance the built-in potential within the device, thereby improving charge-carrier transport and mitigating charge recombination. The organic interfacial layer-modified wide-bandgap PSCs exhibit a high Voc of 1.31V (deficit of <0.44V) and a power conversion efficiency (PCE) of 20.3%, significantly improved from the device without an interface dipole layer (Voc of 1.26V and PCE of 16.7%). Furthermore, the hydrophobic characteristics of the small molecules contribute to improved device stability, retaining 95% of the initial PCE after 500h in ambient air.