Defect Passivation Research Articles

Interfacial engineering and defect passivation of SnO2 through agmatine sulfate in carbon-based perovskite solar cells

Electron transport layer has always played a crucial role in the performance of the perovskite solar cells (PSCs). Particularly, SnO2-based PSC has sparked considerable interest due to its superior properties. Even with such remarkable properties, certain challenges persist such as agglomeration of SnO2 particles which can lead to interfacial defects and poor morphology. To solve this problem, Agmatine Sulfate (AGTS) has been introduced as an interfacial modification agent which with the help of its active functional group including amide (-NH2) and hydroxyl (OH) has allowed to facilitate the interaction at the interface between SnO2 and perovskite. The interaction facilitates the growth of perovskite crystals while tuning the energy levels which has boosted the charge transfer capability of the layer. All these improvements in the properties have led to enhanced power conversion efficiency (PCE) from 11.17 % to 15.20 % for the encapsulated device. Furthermore, the modification also improved the long-term stability of the device as the AGTS-modified devices retained 87 % of their performance at 15–25 °C with humidity levels between 10 and 20 % for over a period of 31 days. Finally, the devices prepared with the AGTS also showed repeatability in their performance while boosting the overall performance of carbon-based PSCs (C–PSCs) and indicating a novel approach to not only increase but also accelerate the commercialization of C-PSC.

Strain-dependence of Te interstitial diffusion in CdTe

While the dominant defects which control non-radiative recombination and long-range interstitial diffusion in CdTe correspond to Cd vacancies and Te anti-sites, the short-range diffusion of Te and Se interstitials between these defects is also of interest, since they both play a role in defect passivation. In addition, since CdTe thin films are typically polycrystalline and may also involve interfaces with materials with different lattice constants, the effects of strain are also of interest. Here we present the results of molecular dynamics (MD) simulations of Te interstitial diffusion in zincblende CdTe for values of the triaxial strain ranging from −2% (compressive) strain to +2.8% (tensile) strain. By carrying out MD simulations of Te interstitial diffusion over a range of temperatures, and then carrying out Arrhenius fits, we have determined the effective activation barrier Ea and prefactor D 0 for each value of the global strain. We find that both Ea and D 0 exhibit non-monotonic behavior, increasing with both compressive and tensile strain. We also present an analysis of the key diffusion pathways for 3 different values of the strain which explains the non-monotonic strain dependence obtained in our simulations. Our results also indicate that in each case, the diffusion of interstitial Te involves a variety of concerted events with a wide range of activation barriers.

Repairing Interfacial Defects in Self-Assembled Monolayers for High-Efficiency Perovskite Solar Cells and Organic Photovoltaics through the SAM@Pseudo-Planar Monolayer Strategy.

Lately, carbazole-based self-assembled monolayers (SAMs) are widely employed as effective hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). Nevertheless, these SAMs tend to aggregate in solvents due to their amphiphilic nature, hindering the formation of a monolayer on the ITO substrate and impeding effective passivation of deep defects in the perovskites. In this study, a series of new SAMs including DPA-B-PY, CBZ-B-PY, POZ-B-PY, POZ-PY, POZ-T-PY, and POZ-BT-PY are synthesized, which are employed as interfacial repairers and coated atop CNph SAM to form a robust CNph SAM@pseudo-planar monolayer as HSL in efficient inverted PSCs. The CNph SAM@pseudo-planar monolayer strategy enables a well-aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss. As a result, the POZ-BT-PY-modified PSC realizes an impressively enhanced solar efficiency of up to 24.45% together with a fill factor of 82.63%. Furthermore, a wide bandgap PSC achieving over 19% efficiency. Upon treatment with the CNph SAM@pseudo-planar monolayer, also demonstrates a non-fullerene organic photovoltaics (OPVs) based on the PM6:BTP-eC9 blend, which achieves an efficiency of 17.07%. Importantly, these modified PSCs and OPVs all show remarkably improved stability under various testing conditions compared to their control counterparts.

Multi‐Point Collaborative Passivation of Surface Defects for Efficient and Stable Perovskite Solar Cells

AbstractThe inherent defects (lead iodide inversion and iodine vacancy) in perovskites cause non‐radiative recombination and there is also ion migration, decreasing the efficiency and stability of perovskite devices. Eliminating these inherent defects is critical for achieving high‐efficiency perovskite solar cells. Herein, an organic molecule with multiple active sites (4,7‐bromo‐5,6‐fluoro‐2,1,3‐phenylpropyl thiadiazole, M4) is introduced to modify the upper interface of perovskites. When M4 interacts with the perovskite surface, the active bromine (Br) site interacts with lead (Pb) at the surface to repair iodine atomic vacancy defects. The fluorine (F) site of M4 interacts with Pb to correct octahedral crystal lattice distortions and eliminate PbI defects. Additionally, sulfur–iodine (S–I) interactions reduce I–I dimerization and eliminate IPb defects. It is also calculated that the energy level of M4 aligns with the band gap, promoting charge transfer. As a result, the perovskite devices achieve an efficiency of 25.1%, a stabilized power output (SPO) of 25.0%, a voltage of 1.19 V, and a fill factor of 85.2%. The device retains 95% of its initial efficiency after 2000 h of ageing in a nitrogen atmosphere. Thus, multi‐point cooperative passivation of surface defects provides an effective method to improve the efficiency and stability of perovskite solar cells.

Defect Passivation Strategies in Two‐Dimensional Organic–Inorganic Hybrid Perovskites for Enhanced Photoelectric Performance

AbstractThe polycrystalline perovskite films treated with solutions inevitably are subjected to high‐density crystal defects, significantly affecting the performance and stability of perovskite‐based photodetectors. In this research, a reasonably designed organic small molecule using piperazine iodide (PI) as an additive is employed to modify the perovskite films. The results indicate that this designed molecule not only improves the crystallinity of the perovskite film but also effectively passivates defects by modifying the local electron density. Consequently, recombination of non‐radiation charges is inhibited, improving the optoelectronic performance and stability of the device. The modified flexible photoelectric device exhibits a responsivity of 3.07 mA W−1 under 405 nm laser illumination. Notably, it maintains a high responsivity even after 7000 bending cycles. Furthermore, generality of the strategy is verified by applying it to various types of two‐dimensional organic–inorganic hybrid perovskite. Additionally, another small molecular amine phthalimide (PTM) is selected as an additive to further verify the universality of this strategy, which reveals that it demonstrates the same passivation as PI. This strategy provides a novel idea for defect passivation of two‐dimensional organic–inorganic hybrid perovskite, signifying a practical application significance for developing flexible wearable devices with optimized performance, perovskite light‐emitting diodes, and solar cells.

Inhibited superoxide‐induced halide oxidation with a bioactive factor for stabilized inorganic perovskite solar cells

AbstractActive oxygen highly affects the efficiency and stability of perovskite solar cells (PSCs) owing to the capacity to either passivate defects or decompose perovskite lattice. To better understand the in‐depth interaction, we demonstrate for the first time that photooxidation mechanism in all‐inorganic perovskite film dominates the phase deterioration kinetics by forming superoxide species in the presence of light and oxygen, which is significantly different from that in organic‒inorganic hybrid and even tin‐based perovskites. In all‐inorganic perovskites, the superoxide species prefer to oxidize longer and weaker Pb‒I bond to PbO and I2, leaving the much stable CsPbBr3 phase. From this chemical proof‐of‐concept, we employ an organic bioactive factor, Tanshinone IIA, as a superoxide sweeper to enhance the environmental tolerance of inorganic perovskite, serving as a “skincare” agent for anti‐aging organisms. Combined with another key point on healing defective lattice, the best carbon‐based all‐inorganic CsPbI2Br solar cell delivers an efficiency as high as 15.12% and superior stability against oxygen, light, humidity, and heat attacks. This method is also applicable to enhance the efficiency of p‒i‒n inverted (Cs0.05MA0.05FA0.9)Pb(I0.93Br0.07)3 cell to 23.46%. These findings not only help us understand the perovskite decomposition mechanisms in depth but also provide a potential strategy for advanced PSC platforms.

Enhancing Orbit–Orbit Interaction and Regulating Defect Passivation in Vacuum-Assisted Flexible Perovskite Films

Enhancing Orbit–Orbit Interaction and Regulating Defect Passivation in Vacuum-Assisted Flexible Perovskite Films

Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots

All-inorganic CsPbI3 perovskite quantum dots (PQDs) hold significant potential for next-generation photovoltaics due to their unique optoelectronic properties, and the surface-bound ligand playing a key role in the stability and functionality of CsPbI3 PQDs. Initially used long-chain ligands in PQDs synthesis stabilize the black phase but hinder charge transport when employed to solar cells, necessitating their replacement with shorter ones. However, this leads to the formation of surface defects and loss of tensile strain, resulting in the transition to the undesired orthorhombic phase (δ-phase) and compromising PQD solar cell performance. Therefore, developing a ligand exchange process that achieves the optimal balance between conductivity and stability in PQD solid films continues to be a significant challenge. To address these issues, we developed an efficient ligand-exchange process utilizing a multifaceted anchoring ligand, 2-thiophenemethylammonium iodide (ThMAI). The larger ionic size of ThMA+ compared to Cs+ facilitates the restoration of surface tensile strain in PQDs, while its thiophene and ammonium groups enable effective passivation of surface defects. Owing to these advantages, ThMAI-treated CsPbI3 PQD thin films exhibit improved carrier lifetime, uniform PQD orientation, and increased ambient stability. As a result, the ThMAI-treated CsPbI3 PQD solar cells demonstrate an improved power conversion efficiency (PCE) of 15.3 % and an enhanced device stability.

High-performance sky-blue quasi-2D perovskite light-emitting diodes via synergistic defect passivation and phase narrowing strategies

Quasi-2D perovskite light-emitting diodes (PeLEDs) are considered as one of the most promising candidates for next-generation displays. Yet, the unstable electroluminescent spectra and inferior performance of blue PeLEDs hinder their commercial use. Herein, we demonstrate highly efficient quasi-2D pure bromide (QPB) sky-blue PeLEDs based on an oxygen-rich triethyl 2-acetylcitrate (TEAC) additive. The TEAC additive contains four C = O functional groups, offering several coordination sites to simultaneously passivate multiple bromine vacancy defects. Furthermore, it inhibits the growth of large n (n ≥ 5) phases to achieve narrow phases distribution. As a result, the TEAC-modified PeLEDs show sky-blue emission at 494 nm, with maximum current efficiency and external quantum efficiency up to 29.1 cd/A and 18.5 %, respectively. Moreover, the T50 lifetime of TEAC-modified PeLED is about 25 times higher than that of pristine PeLEDs. Our results provide a reliable approach to realizing high-efficiency blue quasi-2D PeLEDs.

Surface-binding molecular multipods strengthen the halide perovskite lattice and boost luminescence

Reducing the size of perovskite crystals to confine excitons and passivating surface defects has fueled a significant advance in the luminescence efficiency of perovskite light-emitting diodes (LEDs). However, the persistent gap between the optical limit of electroluminescence efficiency and the photoluminescence efficiency of colloidal perovskite nanocrystals (PeNCs) suggests that defect passivation alone is not sufficient to achieve highly efficient colloidal PeNC-LEDs. Here, we present a materials approach to controlling the dynamic nature of the perovskite surface. Our experimental and theoretical studies reveal that conjugated molecular multipods (CMMs) adsorb onto the perovskite surface by multipodal hydrogen bonding and van der Waals interactions, strengthening the near-surface perovskite lattice and reducing ionic fluctuations which are related to nonradiative recombination. The CMM treatment strengthens the perovskite lattice and suppresses its dynamic disorder, resulting in a near-unity photoluminescence quantum yield of PeNC films and a high external quantum efficiency (26.1%) of PeNC-LED with pure green emission that matches the Rec.2020 color standard for next-generation vivid displays.

Target therapy at buried interfaces toward efficient and stable inorganic perovskite solar cells

The enhancement of power conversion efficiency (PCE) of perovskite solar cells (PSCs) is critically affected by charge recombination induced by buried interface defects. In light of this, a simple and effective target therapy strategy has been developed by doping 4-(diphenylphosphino)benzoic acid (4DBA) molecules at the tin oxide (SnO2)/perovskite interface. The effects of 4DBA on carrier transport, perovskite growth, defect passivation, and PSCs properties were systematically investigated. It is illustrated that 4DBA molecules not only passivate oxygen vacancy (OV) defects on the SnO2 surface, enhancing the conductivity of the SnO2 film and accelerating electron transfer, but also passivate perovskite interface defects, thereby improving the quality of the perovskite film. Ultimately, the efficiency of CsPbBr3 device with 4DBA-modified buried interface increased from 8.87% to 10.78%, an improvement of 21.53%. Furthermore, the efficiency of CsPbI2Br increased from 12.83% to 14.44%, an improvement of 12.55%, further demonstrating the effectiveness and universality of this strategy. Excitingly, the unencapsulated PSCs exhibit excellent long-term stability under high relative humidity and high temperatures.

Components and defect density optimization of FAxMA1-xPbI3 based on simulation for high performance perovskite solar cells

Choosing FA+/MA+ mixed-ion perovskite material as the active layer of the perovskite solar cells hold out the prospect of high efficiency and high stability. In this paper, the FA+/MA + ratio is modified to optimize the performance of FAxMA1-xPbI3-based perovskite solar cells utilizing SCAPS-1D. The results indicate that the PCE of the devices reached a minimum of 21 % when x is greater than or equal to 0.6 in FAxMA1-xPbI3(FTO/NiOx/FAxMA1-xPbI3/C60/BCP/Al). When x = 0.6, the impact of the bottom interface defects on the solar cell performance is dominant and the thickness of the active layer should be controlled within a range of 0.4 μm–0.8 μm, while the defect density of the layer is expected to be between 1013 1/cm3 and 1014 1/cm3. By optimizing the perovskite layer thickness, defect density and changing the type of back electrode material, the efficiency is reaching 25.74 % based on the device(FTO/NiOx/FA6MA4PbI3/C60/BCP/Au). This study provides theoretical guidance for experimental research on interface modification, defect passivation and manufacturing of high-efficiency FAxMA1-xPbI3-based perovskite solar cells.

Front Cover: Revealing the Roles of Guanidine Hydrochloride Ionic Liquid in Ion Inhibition and Defects Passivation for Efficient and Stable Perovskite Solar Cells (ChemSusChem 14/2024)

Front Cover: Revealing the Roles of Guanidine Hydrochloride Ionic Liquid in Ion Inhibition and Defects Passivation for Efficient and Stable Perovskite Solar Cells (ChemSusChem 14/2024)

Synergistic Crystallization Modulation and Defects Passivation in Kesterite via Anion-Coordinate Precursor Engineering for Efficient Solar Cells.

It has been validated that enhancing crystallinity and passivating the deep-level defect are critical for improving the device performance of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Coordination chemistry interactions within the Cu-Zn-Sn-S precursor solution play a crucial role in the management of structural defects and the crystallization kinetics of CZTSSe thin films. Therefore, regulating the coordination environment of anion and cation in the precursor solution to control the formation process of precursor films is a major challenge at present. Herein, a synergetic crystallization modulation and defect passivation method is developed using P2S5 as an additive in the CZTS precursor solution to optimize the coordination structure and improve the crystallization process. The alignment of theoretical assessments with experimental observations confirms the ability of the P2S5 molecule to coordinate with the metal cation sites of CZTS precursor films, especially more liable to the Zn2+, effectively passivating the Zn-related defects, thereby significantly reducing the defect density in CZTSSe absorbers. As a result, the device with a power conversion efficiency of 14.36% has been achieved. This work provides an unprecedented strategy for fabricating high-quality thin films by anion-coordinate regulation and a novel route for realizing efficient CZTSSe solar cells.

Ultrahigh Performance UV Photodetector by Inserting an Al2O3 Nanolayer in NiO/n‐Si

AbstractUltraviolet (UV) photodetectors have gained much attention due to their numerous important applications ranging from environmental monitoring to space communication. To date, most p‐NiO/n‐Si heterojunction photodetectors (HPDs) exhibit poor UV responsivity and slow response. This is mainly due to a small valence band offset (ΔEV) at the NiO/Si interface and a high density of dangling bonds at the silicon surface. Herein, an UV HPD consisting of NiO/Al2O3/n‐Si is fabricated using magnetron sputtering technique. The HPD has a large rectification ratio of 2.4 × 105. It also exhibits excellent UV responsivity (R) of 15.8 A/W at −5 V and and detectivity (D*) of 1.14 × 1013 Jones at −4 V, respectively. The excellent performance of the HPD can be attributed to the defect passivation at the interfaces of the heterojunction and the efficient separation of photogenerated carriers by the Al2O3 nanolayer. The external quantum efficiency (EQE) of the HPD as high as 5.4 × 103%, hence implying a large optical gain due to carrier proliferation resulting from impact ionization. Furthermore, the ultrafast response speed with a rise time of 80 µs and a decay time of 184 µs are obtained.

Enhancing Efficiency and Durability of Perovskite Solar Cells with Chlorine‐Functionalized Fully Conjugated Porous Aromatic Framework

Non‐radiative recombination, caused by trap states, significantly hampers the efficiency and stability of perovskite solar cells (PSCs). The emerging porous organic polymers (POPs) show promise as a platform for designing novel defect passivation agents due to their rigid and porous structure. However, the POPs reported so far lack either sufficient stability or clear sites of interactions with the defects. Herein, two chlorine‐functionalized, fully conjugated porous aromatic frameworks (PAFs) were constructed via a decarbonylation reaction. The chlorinated PAFs feature unique long‐range conjugated networks bearing multiple chlorine atoms, significantly improving the photovoltaic performance and stability of doped solar cells. Combined experimental and theoretical analyses confirmed the strong passivation effects of conjugated structure to the defect through Cl sites. Specifically, PAF‐159, bearing a triphenylamine moiety, demonstrated stronger Cl‐Pb bonding and higher passivation efficiency due to the presence of π* anti‐bonding orbitals, which elevate the HOMO energy level and facilitate Cl‐Pb charge transfer. Consequently, we obtained high‐performance PAF‐159‐doped devices with advanced PCE (24.3%), good storage stability (retaining 86% after 3000 hours), and good long‐term operational stability (retaining 92% after 350 hours)

Enhancing Efficiency and Durability of Perovskite Solar Cells With Chlorine-Functionalized Fully Conjugated Porous Aromatic Framework.

Non-radiative recombination, caused by trap states, significantly hampers the efficiency and stability of perovskite solar cells (PSCs). The emerging porous organic polymers (POPs) show promise as a platform for designing novel defect passivation agents due to their rigid and porous structure. However, the POPs reported so far lack either sufficient stability or clear sites of interactions with the defects. Herein, two chlorine-functionalized, fully conjugated porous aromatic frameworks (PAFs) were constructed via a decarbonylation reaction. The chlorinated PAFs feature unique long-range conjugated networks bearing multiple chlorine atoms, significantly improving the photovoltaic performance and stability of doped solar cells. Combined experimental and theoretical analyses confirmed the strong passivation effects of conjugated structure to the defect through Cl sites. Specifically, PAF-159, bearing a triphenylamine moiety, demonstrated stronger Cl-Pb bonding and higher passivation efficiency due to the presence of π* anti-bonding orbitals, which elevate the HOMO energy level and facilitate Cl-Pb charge transfer. Consequently, we obtained high-performance PAF-159-doped devices with advanced PCE (24.3 %), good storage stability (retaining 86 % after 3000 hours), and good long-term operational stability (retaining 92 % after 350 hours).

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.

Comparative study of cesium halide (CsX, X = I, Cl, Br) modifications on defect passivation in tin-based perovskite solar cells

Comparative study of cesium halide (CsX, X = I, Cl, Br) modifications on defect passivation in tin-based perovskite solar cells

The Crystallization Regulation Effect of the Phenyl Ring of Passivators for Blue Perovskite Light-Emitting Diodes.

Although metal halide perovskites (MHPs) have demonstrated remarkable external quantum efficiencies (EQEs) in red and green light-emitting diodes (LEDs), the blue ones confront efficiency and stability problems due to the high defect density in the perovskite films. Large amounts of defect passivation strategies are successfully developed to improve the device performance. Nevertheless, the influence of the molecular configuration of the passivators on the perovskite crystallization process has not been comprehensively investigated so far. Here, we investigate the effect of the phenyl ring on the perovskite crystallization dynamics and the passivation effect. The additive with a phenyl ring performs the π-π stacking ability with phenethylammonium (PEA+) molecules, resulting in a deteriorated crystallinity and a weakened passivation ability. Conversely, the additive without the phenyl ring is helpful to promote the participation of PEA+ molecules in the crystalline process, leading to a higher crystallinity and a stronger passivation effect. As a result, the EQE of the blue perovskite LED has increased from 4.72 to 11.06% by using the phenyl ring-free additive. Therefore, it is advisible to develop the conjugated nonplanar additives in the PEA+-assisted quasi-two-dimensional perovskites. This finding may enlighten the rational design of defect passivators for highly efficient perovskite LEDs.