Reduction Of Defect Density Research Articles

Enhanced Performance of Sn-Based Perovskite Photodetectors Through Double-Sided Passivation for Near-Infrared Applications.

The development of high-performance Sn-based perovskite photodetectors is presented with double-sided passivation using large alkylammonium interlayers of PEAI and BDAI₂. This dual passivation strategy, applied to the top and bottom of FASnI₃ films, effectively improves film quality by reducing defect density, enhancing carrier mobility, and minimizing non-radiative energy losses at the interfaces. At 720nm, the photodetectors demonstrate a responsivity of 0.37AW-1, a detectivity of 6.12×10¹3 Jones, and an external quantum efficiency (EQE) of 65.60%, with a rapid response time of 9 µs. Additionally, at 850nm, the detectivity reaches as high as 3.27 × 10¹3 Jones. Furthermore, the device demonstrated a low 1/f noise of 1.21 × 10⁻¹⁵ AHz⁻⁰.⁵ at 10Hz. Transient photocurrent (TPC) and transient photovoltage (TPV) measurements revealed a significant increase in charge recombination lifetime (τe) and improved charge transfer efficiency. These results showcase the potential of Sn perovskite photodetectors for near-infrared applications, including autonomous vehicles, biometric recognition, and biomedical treatments.

Carboxymethyl‐Based Ionic Liquid Engineering for Efficient and Stable Inverted Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered significant attention due to their tunable bandgap, superior charge carrier properties, and easy fabrication processes, making them highly efficient energy conversion devices. Despite these advantages, nonradiative recombination due to defects in the perovskite layer continues to limit performance. This study addresses this issue by introducing 1‐CarboxyMethyl‐3‐MethylImidazolium chloride (ImAcCl) into precursor solution to enhance film quality and suppress defect‐induced recombination. The carboxylate groups (CO) and hydrogen donors (NH) in ImAcCl form coordination and hydrogen bonds, helping to reduce defect density of the perovskite film. Additive ImAcCl improves crystallinity, reduces surface roughness, and enhances charge carrier transport, leading to higher photovoltaic performance. With the ImAcCl additive, the power conversion efficiency and short‐circuit current of PSCs significantly improve by 23.92% and 25.35 mA cm−2, with a notable reduction in nonradiative recombination losses. This study highlights the significant potential of ImAcCl as an effective additive for defect passivation in PSCs, offering a promising pathway toward further efficiency improvements in next‐generation solar cells.

Enhancing Flexibility, Long-Term Stability, and Efficiency in Full Air Fabricated Perovskite Solar Cells via Multifunctional Fluorinated Polyurethane Additives.

Perovskite films often suffer from surface and grain boundary defects, including uncoordinated ions, lattice distortions, and dangling bonds, coupled with lattice distortions due to solvent volatilization anisotropy and the thermal expansion coefficient. Such defects severely compromise both the photovoltaic efficiency and long-term solar cell stability. Here, fluorinated polyurethane (FPU) was synthesized and introduced into the perovskite precursor as a multifunctional additive. Excess Pb2+ ions interact with the carbonyl group (C═O) of FPU, thereby reducing nonradiative recombination. The perovskite and FPU form various hydrogen bonds via MA+ with F and -NH with -I. This multiplies the passivation of grain boundary defects, increases grain size, reduces defect density, releases residual lattice stress, and facilitates charge transport. Accordingly, the power conversion efficiency of the FPU-modified perovskite solar cells (PSCs) on rigid substrates and flexible substrates reached 21.18 and 17.76%, respectively. Notably, the long-chain C-F compound, which constructs a moisture-resistant barrier, could inhibit moisture corrosion in the perovskite films. After 2000 h of storage at ambient temperature in dark, the PSCs's initial efficiency still remained 82%. Additionally, after it undergoes 300 bending cycles (r = 0.7 cm), the device maintains 92.4% of its initial efficiency.

CsF Improved Buried Interface for Efficient and Stable Inverted All-inorganic CsPbI2.85Br0.15 Perovskite Solar Cells

All-inorganic CsPbIxBr3-x is frequently used as the top cells in tandem devices due to its tunable bandgap, making it highly promising for future development. However, CsPbIxBr3-x films typically contain numerous defects at the interfaces and grain boundaries, significantly hindering carrier transport and thus reducing the device performance. Interface modification is commonly employed to passivate defects and enhance carrier transport at the interfaces. In this work, CsF was used to modify the buried interface between the perovskite film and self-assembled monolayers (SAMs). The interaction between fluoride ions (F⁻) and uncoordinated Pb2⁺ contributed to reduce defect density, enhance crystallization quality, and suppress non-radiative carrier recombination at buried interface. Consequently, the efficiency of inverted CsPbI2.85Br0.25 PSCs with CsF improved from 16.15% to 18.24%, compared to the control device. Moreover, the unencapsulated CsF-modified device retained 89% of its initial efficiency after storing for 600 h in ambient air with room-temperature and relative humidity (RH) of 20%. This demonstrates that CsF modification significantly enhances both the performance and stability of CsPbI2.85Br0.15 perovskite solar cells.

Epitaxial films and devices of transparent conducting oxides: La:BaSnO3

This paper reviews recent developments in materials science and device physics of high-quality epitaxial films of the transparent perovskite La-doped barium stannate, La:BaSnO3. It presents current efforts in the synthesis science of epitaxial La:BaSnO3 films for achieving reduced defect densities and high electron mobility at room temperature. We discuss the scattering mechanisms and the route toward engineering defect-free epitaxial La:BaSnO3 heterostructures. By combining chemical surface characterization and electronic transport studies, special emphasis is laid on the proper correlation between the transport properties and the electronic band structure of La:BaSnO3 films and heterostructures. For application purposes, interesting optical properties of La:BaSnO3 films are discussed. Finally, for their potential application in oxide electronics, an overview of current progress in the fabrication of La:BaSnO3-based thin-film field-effect transistors is presented together with recent progress in the fundamental realization of two-dimensional electron gases with high electron mobility in La:BaSnO3-based heterostructures. Future experimental studies to reveal the potential deployment of La:BaSnO3 films in optoelectronic and transparent electronics are also discussed.

Tuning leakage current and ferroelectric properties in spin-coated BiFeO3 films through Cr doping and post-annealing atmosphere control

Effective enhancement of ferroelectric properties in BiFe1-xCrxO3 films prepared via the sol-gel method is crucial. Here, by adjusting the Cr content, BiFe1-xCrxO3 films with smooth surfaces and uniform grain structures were successfully synthesized. X-ray photoelectron spectroscopy (XPS) analyses revealed that Cr doping significantly reduces the concentrations of Fe2+ and oxygen vacancies within the BFO films, thereby mitigating leakage currents and enhancing ferroelectricity. Additionally, we investigated the microstructure and electrical characteristics of BiFe0.98Cr0.02O3 thin films subjected to post-annealing in different atmospheres (N2, Air, and O2). Notably, annealing in an O2 atmosphere notably enhanced the crystallinity and grain uniformity of BiFe0.98Cr0.02O3 thin films. This treatment resulted in superior ferroelectric polarization switching behavior, achieving the highest remanent polarization (Pr = 153.1 μC/cm2) due to reduced defect densities. Our findings underscore the critical roles of Cr3+ ions and O2 annealing atmospheres in suppressing leakage currents and boosting ferroelectric properties in BFO films.

(Invited) Vacuum-Processable Additive for Controlling Growth of Perovskite Crystals in All Vacuum Processed Perovskite Solar Cell

We present a novel method for controlling the growth of perovskite crystals in a vacuum thermal evaporation process by utilizing a vacuum-processable additive, propylene urea (PU). Co-evaporating of perovskite precursors and PU retards the direct reaction between the perovskite precursors. This facilitates larger domain size and reduced defect density. In this study, we present a novel method for controlling the growth of perovskite crystals in a vacuum thermal evaporation process by utilizing a vacuum-processable additive, propylene urea (PU). By co-evaporating perovskite precursors with PU to form the perovskite layer (Figure1), PU, acting as a Lewis base additive, retards the direct reaction between the perovskite precursors. This facilitates larger domain size and reduced defect density (Figure 2). Following the removal of the residual additive, the perovskite layer, exhibiting improved crystallinity, demonstrates reduced charge recombination, as confirmed by time-resolved microwave conductivity analysis. Consequently, there is a notable enhancement in open-circuit voltage and power conversion efficiency, increasing from 1.05 V to 1.15 V and from 17.17% to 18.31%, respectively. The incorporation of a vacuum-processable and removable Lewis’s base additive into the fabrication of vacuum-processed perovskite solar cells offers new avenues for optimizing these devices. Figure 1

Efficient Blade-Coated Wide-Bandgap and Tandem Perovskite Solar Cells via a Three-Step Restraining Strategy.

Blade-coating techniques have attracted significant attention for perovskite solar cells (PSCs)due to their high precursor utilization and simplicity. However, the power conversion efficiency (PCE) of blade-coated PSCs often lags behind that of spin-coated devices, mainly due to difficulties in precisely controlling perovskite film formation during pre-nucleation, heterogeneous nucleation, and crystallization in the blade-coating and N2-knife drying processes. In this work, a three-step restraining strategy is introduced utilizing functional glycine amide hydrochloride to regulate pre-nucleation clustering, suppress excessive heterogeneous nucleation, and decelerate crystallization, enabling comprehensive control of the perovskite film formation processes. This approach results in enlarged grains, reduced defect densities, and highly oriented crystalline wide-bandgap perovskite films with significantly prolonged carrier lifetimes, achieving a maximum PCE of 19.97% for 1.77 eV-bandgap blade-coated PSCs. Furthermore, two-terminal tandem cells, composed of wide-bandgap perovskite top cells and 1.25 eV-bandgap perovskite bottom cells fabricated via blade coating, yield an impressive PCE of 27.11% (stabilized at 26.87%). This study offers comprehensive insights into controlling pre-nucleation, heterogeneous nucleation, and crystallization during blade coating, providing valuable guidance for developing high-performance, large-area devices in the future.

6-Trifluoromethylnicotinamide Bilaterally Anchored All Cations Implementing Efficient and Humidity-Stable Perovskite Solar Cells.

For organic-inorganic hybrid perovskite solar cells (PSCs), the volatilization of organic components and the presence of undercoordinated Pb2+ ions are the primary causes of device stability imbalance. These factors also serve as significant determinants that restrict the commercialization scale of PSCs. Here, 6-trifluoromethylnicotinamide (TNA) molecules, featuring amide and trifluoromethyl groups at both ends, were introduced as Lewis additives into the precursor solution of perovskite to anchor all cation defect sites and optimize the crystallization process of perovskite. Theoretical calculations confirmed that the -NH2 and C═O groups within the amide group on one side of the TNA molecule synergistically passivated the undercoordinated Pb2+ ions, whereas the trifluoromethyl group on the other side formed hydrogen bonds with the organic components of perovskite. The scorpion-like bilateral all-cation anchoring ability of TNA molecules was further substantiated through experimental characterization. Upon optimization of the TNA treatment concentration, a perovskite film characterized by large grains and a reduced defect density of states was achieved. The photovoltaic performance of PSCs incorporating TNA exhibited significant enhancement with an increase in efficiency from 22.42% (Control) to 24.15%. Under a harsh high-humidity environment, the comprehensive cation passivation effect of TNA significantly hindered the decomposition and phase transition of perovskite films, thereby ensuring excellent humidity stability for the PSCs.

Oxide-nitride nanolayer stacks for enhanced passivation of p-type surfaces in silicon solar cells

In the quest for ultra-high-efficiency silicon solar cells, optimising surface passivation has emerged as a critical pathway to minimise losses and enhance device performance. Recent breakthroughs in aluminium oxide (AlOx) passivation show an interface to Si with low interface defect density and high negative charge density after activation annealing at 400–450 °C, enabling low surface recombination velocities. The formation of an interfacial SiOx layer has been recognised as a key factor. In this study, we present an in-depth investigation of a SiOx/AlOx/SiNx nanolayer stack interface with Si, where the SiOx is wet chemically grown. By varying the AlOx deposition from 5 to 40 ALD cycles, we observed a reduction in interface defect density, indicating the presence of negatively charged hydrogen in the AlOx layer. We reveal a distinctly different interface between Si and nanolayer stacks with or without AlOx. Activation annealing significantly reduced recombination losses for stacks with AlOx, attributed to increased charge density and decreased carrier capture velocity at the valence band-tail. We find lower electron capture rates in nanolayer stacks containing AlOx, suggesting effective passivation of donor states by negatively charged hydrogen. Additionally, the formation of new acceptor states was detected by an increase in hole capture velocity at the interface after annealing. Electron energy loss spectroscopy (EELS) identified an Al:SiOxNy layer of ∼2.5 nm thick with excess oxygen content and a mixture of tetrahedral and octahedral coordinated Al, likely contributing to the formation of acceptor defects and suggest an intrinsic link between the chemical and field-effect passivation.

All-In-One Additive Enabled Efficient and Stable Narrow-Bandgap Perovskites for Monolithic All-Perovskite Tandem Solar Cells.

Hybrid tin-lead (Sn-Pb) perovskites have garnered increasing attention due to their crucial role in all-perovskite tandem cells for surpassing the efficiency limit of single-junction solar cells. However, the easy oxidation of Sn2+ and fast crystallization of Sn-based perovskite present significant challenges for achieving high-quality hybrid Sn-Pb perovskite films, thereby limiting the device's performance and stability. Herein, an all-in-one additive, 2-amino-3-mercaptopropanoic acid hydrochloride (AMPH) is proposed, which can function as a reducing agent to suppress the formation of Sn4+ throughout the film preparation. Furthermore, the strong binding between AMPH and Sn-based precursor significantly slows down the crystallization process, resulting in a high-quality film with enhanced crystallinity. The remaining AMPH and its oxidation products within the film contribute to improves oxidation resistance and a substantial reduction in defect density, specifically Sn vacancies. Benefiting from the multifunctionalities of AMPH, a power conversion efficiency (PCE) of 23.07% is achieved for single-junction narrow-bandgap perovskite solar cells. The best-performing monolithic all-perovskite tandem cell also exhibits a PCE of 28.73% (certified 27.83%), which is among the highest efficiency reported yet. The tandem devices can also retain over 85% of their initial efficiencies after 500 hours of continuous operation at the maximum power point under one-sun illumination.

Hexafluoroisopropanol modified MXene for perovskite surface remodeling and interfacial dipole effect enhancement

The development of high-efficiency and stable perovskite (PVK) solar cells (PSCs) still faces the challenge of non-ideal interfaces between PVK and charge transport layers. Herein, the hexafluoroisopropanol (HFIP) modified two-dimensional Ti3C2Tx MXene is custom-made (MX-HFIP) and employed as the interlayer between the PVK and hole transport layer (HTL) interface by forming hydrogen bonds. The MX-HFIP serves to reinforce the interface contact and remodel the surface of PVK, leading to a high-quality PVK film with a significantly reduced defect density, suppressed nonradiative recombination, and inhibited invasion of water and oxygen. Moreover, the synergistic effect of MXene and HFIP results in an enhanced interfacial dipole effect and an optimized energy-level alignment, thereby increasing the driving force for charge extraction and transport at the PVK/HTL interface. Therefore, the MX-HFIP treated PSC achieves a substantially-enhanced power conversion efficiency (PCE) of 22.33 %, as compared to 20.05 % of the untreated device. Besides, the MX-HFIP treated PSC delivers significantly enhanced stabilities, with 88 % of its initial PCE after 1656 h of storage at 25 °C under 30 %⁓40 % relative humidity. These findings demonstrate the advancement using fluorine-rich molecule modified MXene to improve interfacial properties for enhancing performances and stabilities of optoelectronic devices.

Defect enriched luminescent MXene-derived TiO2 for supercapacitors

To utilize the intriguing properties of MXene and titania, here in this work, we have synthesized defect-enriched TiO2 by thermal annealing of MXene phase (Mxene-derived-TiO2) and characterized using X-ray diffraction, Raman spectroscopy, Field emission, and transmission electron microscopy. Such uniquely derived MXene-derived-TiO2 displayed bright blue light photoluminescence (PL) under near UV excitation. The electrochemical analysis underscores the superior electrochemical performance of MXene-derived-TiO2, particularly in terms of specific capacitance and pseudocapacitive behavior, making them highly suitable for supercapacitors. The oxygen and titanium vacancies present in MXene-derived-TiO2 are responsible for its excellent PL and supercapacitor action. Such defect-induced origin of PL and supercapacitive action is further validated by the addition of NiO. Electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) suggested addition of NiO to Mxene-derived-TiO2 leads to a reduction in defect density of titanium vacancies and is reflected in the lowering of PL intensity and resulted in inferior supercapacitive properties.

Quantum-Confined Perovskite Nanocrystals Enabled by Negative Catalyst Strategy for Efficient Light-Emitting Diodes.

The perovskite nanocrystals (PeNCs) are emerging as a promising emitter for light-emitting diodes (LEDs) due to their excellent optical and electrical properties. However, the ultrafast growth of PeNCs often results in large sizes exceeding the Bohr diameter, leading to low exciton binding energy and susceptibility to nonradiative recombination, while small-sized PeNCs exhibit a large specific surface area, contributing to an increased defect density. Herein, Zn2+ ions as a negative catalyst to realize quantum-confined FAPbBr3 PeNCs with high photoluminescence quantum yields (PL QY) over 90%. Zn2+ ions exhibit robust coordination with Br- ions is introduced, effectively retarding the participation of Br- ions in the perovskite crystallization process and thus facilitating PeNCs size control. Notably, Zn2+ ions neither incorporate into the perovskite lattice nor are absorbed on the surface of PeNCs. And the reduced growth rate also promotes sufficient octahedral coordination of PeNC that reduces defect density. The LEDs based on these optimized PeNCs exhibits an external quantum efficiency (EQE) of 21.7%, significantly surpassing that of the pristine PeNCs (15.2%). Furthermore, the device lifetime is also extended by twofold. This research presents a novel approach to achieving high-performance optoelectronic devices.

Ionic Liquid-Assisted Strategy for Morphology Engineering of Inorganic Cesium-Based Perovskite Thin Films Toward High-Performance Solar Cells.

The wide bandgap CsPbI2Br perovskite materials have attracted significant attention due to their high thermal stability and compatibility with narrow bandgap materials in tandem devices. The performance of perovskite solar cells (PSCs) is highly dependent on the quality of the perovskite layer, which is governed by the crystallization process during solution processing. However, the crystallization dynamics of CsPbI2Br thin films remain less explored compared to conventional organic-inorganic perovskites. Achieving high-quality CsPbI2Br films with uniform morphology and large perovskite grains remains challenging with standard solution techniques. This study applies the ionic liquid (IL) [EMIM]+[PF6]- as an additive within the bulk CsPbI2Br absorber layer. Within our experimental regime, [EMIM]+[PF6]- accelerates the crystallization process while promoting the formation of large perovskite grains, a feature not commonly observed in previous studies. Our experimental results suggest that the IL acts as heterogeneous nucleation sites, and varying IL incorporation amount significantly impacts the morphology of CsPbI2Br perovskite films. Consistent UV-vis and photoluminescence (PL) red-shifts are observed in the IL-incorporated CsPbI2Br films, with X-ray diffraction (XRD) data projecting an influence on the perovskite crystal structure. These findings provide new insights into the role of ILs in controlling crystallization and morphology that have been minimally discussed in the literature. The incorporation of an optimized amount of [EMIM]+[PF6]- promotes the formation of highly crystalline perovskite thin films with excellent morphology, reducing defect density, enhancing carrier transport, and yielding large grain sizes. As a result, PSCs fabricated with [EMIM]+[PF6]- achieved a power conversion efficiency (PCE) of 17.11% (stabilized at 15.87%) and an open-circuit voltage (VOC) of 1.39 V, along with improved stability compared to control devices. This work provides a straightforward approach for producing high-quality CsPbI2Br thin films with high reproducibility, contributing valuable advancements to Cs-based PSCs.

Enhanced Performance of Close-Spaced Sublimation Processed Antimony Sulfide Solar Cells via Seed-Mediated Growth.

Antimony sulfide (Sb2S3) has attracted much attention due to its great prospect to construct highly efficient, cost-effective, and environment-friendly solar cells. The scalable close-spaced sublimation (CSS) is a well-developed physical deposition method to fabricate thin films for photovoltaics. However, the CSS-processed absorber films typically involve small grain size with high-density grain boundaries (GBs), resulting in severe defects-induced charge-carrier nonradiative recombination and further large open-circuit voltage (VOC) losses. In this work, it is demonstrated that a chemical bath deposited-Sb2S3 seed layer can serve as crystal nuclei and mediate the growth of large-grained, highly compact CSS-processed Sb2S3 films. This seed-mediated Sb2S3 film affords reduced defect density and enhanced charge-carrier transport, which yields an improved power conversion efficiency (PCE) of 4.78% for planar Sb2S3 solar cells. Moreover, the VOC of 0.755V that is obtained is the highest reported thus far for vacuum-based evaporation and sublimation processed Sb2S3 devices. This work demonstrates an effective strategy to deposit high-quality low-defect-density Sb2S3 films via vacuum-based physical methods for optoelectronic applications.

Performance enhancement of MOCVD grown Zn-doped β-Ga2O3 Deep-Ultraviolet photodetectors on silicon substrates via TiN buffer layers

Integrating β-Ga2O3-based devices on silicon substrates faces challenges due to lattice and thermal expansion mismatches, leading to performance-degrading defects. Therefore, this work explores the utilization of a titanium nitride (TiN) buffer layer in order to enhance the performance of MOCVD grown Zn-doped β-Ga2O3-based deep-ultraviolet (DUV) photodetectors (PDs) on silicon substrates with 12, 24, and 36 sccm diethylzinc (DEZn) flow rates. The XPS depth profiles revealed the presence of TiN buffer layer in β-Ga2O3/TiN/Si films, which served as a diffusion barrier during deposition, preserving interface integrity and reducing defect density. Zn-doped β-Ga2O3/TiN/Si based DUV PDs revealed remarkable results. The 12 sccm Zn-doped β-Ga2O3/TiN/Si PDs demonstrated an exceptional maximum responsivity of 31.4 A/W, which is 7 times higher compared to the undoped β-Ga2O3/TiN/Si (4.47 A/W) under a 5 V bias and 240 nm wavelength illumination. This PD exhibited the detectivity of 1.68 × 1013 Jones and EQE of 1.63 × 104 %. This PD possess quick rise time of 6.5 s and fall time of 0.5 s. The energy band diagram for Zn-doped β-Ga2O3/TiN/Si metal–semiconductor-metal type PDs is discussed. This work demonstrates that TiN buffer layers and Zn doping significantly improve the performance and reliability of β-Ga2O3-based DUV photodetectors on silicon substrates.

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.

Vertical Compositional Heterogeneity Induces Instability in All-Inorganic CsPbIBr2 Perovskites.

Understanding the vertical compositional homogeneity and defect distribution is of paramount importance in elucidating and maximizing the performance of halide-perovskite-based optoelectronic devices. This work reports the depth-dependent study of the chemical composition and metallic Pb0 content of all-inorganic CsPbIBr2 perovskite films undertaken using lab-based hard X-ray photoelectron spectroscopy and soft X-ray photoelectron spectroscopy. The presence of elemental or metallic Pb (Pb0), in the bulk and at the surface of the perovskite films highlights the formation of defect or recombination centers throughout the analyzed depth. The Pb0 content was found to be of higher concentration in the bulk of the CsPbIBr2 films compared to that at the surface. Engineering the CsPbIBr2 film growth using appropriate antisolvents resulted in the overall reduction and/or complete elimination of Pb0 at the surface and at the bulk of the perovskite films. However, the effect of antisolvent treatment was significantly pronounced in the bulk-like region as compared to that at the surface. Pb0 is synonymous with defect states/recombination centers in perovskite films and this reduction in defect density due to the antisolvent treatment corroborates the enhanced phase stability and improved solar cell performance of the corresponding CsPbIBr2 devices.

Enhancing Performance and Stability of Perovskite Solar Cells with a Novel Formamidine Group Additive.

Perovskite materials, particularly FAPbI3, have emerged as promising candidates for solar energy conversion applications. However, these materials are plagued by well-known defects and suboptimal film quality. Enhancing crystallinity and minimizing defect density are therefore essential steps in the development of high-performance perovskite solar cells. In this study, 1H-Pyrazole-1-carboximidamide hydrochloride (PCH) is introduced into FAPbI3 perovskite films. The molecular structure of PCH features a pyrazole ring bonded to formamidine (FA). The FA moiety of PCH facilitated the incorporation of this additive into the film lattice, while the negatively charged pyrazole ring effectively passivated positively charged iodine vacancies. The presence of PCH led to the fabrication of an FAPbI3 device with improved crystallinity, a smoother surface, and reduced defect density, resulting in enhanced Voc and fill factor. A record power conversion efficiency of 24.62% is achieved, along with exceptional stability under prolonged air exposure and thermal stress. The findings highlight the efficacy of PCH as a novel additive for the development of high-performance perovskite solar cells.