Passivation Of Surface Defects Research Articles

Enhanced Performance and Stability of CsPbBr3 Perovskite Solar Cells Using Trioctylphosphine Oxide Additive.

This study investigates the application of trioctylphosphine oxide (TOPO) and triphenylphosphine oxide (TPPO) as an additive to enhance the performance of all-inorganic CsPbBr3 perovskite solar cells (PSCs). The addition of TOPO and TPPO passivates surface defects, increases grain size, and reduces surface trap states, leading to better light absorption and accelerated carrier transport. These modifications lead to an optimized energy level distribution, resulting in a significant increase in power conversion efficiency from 5.14 to 9.21% with TOPO and from 5.14% to 7.28% with TPPO. Furthermore, the long alkyl chains in TOPO provide effective isolation from air and water, significantly enhancing device stability for over 2400 h without packaging. The findings demonstrate that oxygen phosphine additives with long alkane chains are more effective in improving PSCs than those with aromatic hydrocarbons, offering new insights for the use of passivators in perovskite solar cells.

Synergistic Modulation of Orientation and Steric Hindrance Induced by Alkyl Chain Length in Ammonium Salt Passivator Toward High‐performance Inverted Perovskite Solar Cells and Modules

AbstractOrganic ammonium salts are extensively utilized for passivating surface defects in perovskite films to mitigate trap‐assisted nonradiative recombination. However, the influence of alkyl chain length on the molecular orientation and spatial steric hindrance of ammonium salt remains underexplored, hindering advancements in more effective passivators. Here, a series of organic ammonium salts is reported with varying alkyl chain lengths to passivate surface defects and optimize band alignment. It is revealed that long alkyl chains promote parallel molecular orientation on the perovskite surface, thereby reinforcing interaction with surface defects, whereas excessive chain length introduces steric hindrance, weakening anion‐perovskite interactions. Nonylammonium acetate (NAAc) with optimal chain length achieves the ideal balance between chemical interactions, resulting in superior passivation. Through NAAc passivation, high‐performance inverted perovskite solar cells (PSCs) and modules are achieved, with power conversion efficiencies (PCE) of 25.79% (certified 25.12%) and 19.62%, respectively. This marks a record PCE for inverted PSCs utilizing vacuum flash technology in ambient conditions. Additionally, the NAAc‐passivated devices retain 91% of their initial PCE after 1200 h of continuous maximum power point operation. This work offers new insights into the interplay between molecular orientation and steric hindrance, advancing the design of high‐performance PSCs.

Enhancing the Efficiency and Stability of Inverted Perovskite Solar Cells and Modules through Top Interface Modification with N‐type Semiconductors

The interface modification between perovskite and electron transport layer (ETL) plays a crucial role in achieving high performance inverted perovskite photovoltaics (i‐PPVs). Herein, non‐fullerene acceptors (NFAs), known as Y6‐BO and Y7‐BO, were utilized to modify the perovskite/ETL interface in i‐PPVs. Non‐polar solvent‐soluble NFAs can effectively passivate surface defects without structural damage of the underlying perovskite films. Additionally, the improved PCBM ETL induced by NFAs modification significantly accelerates the electrons extraction. As a result, both Y6‐BO and Y7‐BO exhibit more effective interface modification effects compared to traditional PI molecules. The power conversion efficiency (PCE) of the inverted perovskite solar cell (i‐PSC) modified with Y7‐BO reaches 25.82%. Moreover, the adoption of non‐polar solvents and the superior semiconductor properties of Y7‐BO molecules also enable perovskite solar modules (i‐PSM) with effective areas of 50 cm2, 400 cm2, and 1160 cm2 to achieve record efficiencies of 23.05%, 22.32%, and 21.1% (certified PCE), respectively, making them the best PCE reported in the literature. Importantly, enhanced interface mechanical strength between the perovskite and PCBM layer results in significantly improved environmental and operational stability of the cells. The cells modified with Y7‐BO maintained 94.4% of the initial efficiency after 1522 hours of maximum power point aging.

Enhancing the Efficiency and Stability of Inverted Perovskite Solar Cells and Modules through Top Interface Modification with N-type Semiconductors.

The interface modification between perovskite and electron transport layer (ETL) plays a crucial role in achieving high performance inverted perovskite photovoltaics (i-PPVs). Herein, non-fullerene acceptors (NFAs), known as Y6-BO and Y7-BO, were utilized to modify the perovskite/ETL interface in i-PPVs. Non-polar solvent-soluble NFAs can effectively passivate surface defects without structural damage of the underlying perovskite films. Additionally, the improved PCBM ETL induced by NFAs modification significantly accelerates the electrons extraction. As a result, both Y6-BO and Y7-BO exhibit more effective interface modification effects compared to traditional PI molecules. The power conversion efficiency (PCE) of the inverted perovskite solar cell (i-PSC) modified with Y7-BO reaches 25.82%. Moreover, the adoption of non-polar solvents and the superior semiconductor properties of Y7-BO molecules also enable perovskite solar modules (i-PSM) with effective areas of 50 cm2, 400 cm2, and 1160 cm2 to achieve record efficiencies of 23.05%, 22.32%, and 21.1% (certified PCE), respectively, making them the best PCE reported in the literature. Importantly, enhanced interface mechanical strength between the perovskite and PCBM layer results in significantly improved environmental and operational stability of the cells. The cells modified with Y7-BO maintained 94.4% of the initial efficiency after 1522 hours of maximum power point aging.

2,2′‐Bipyridyl‐4,4′‐Dicarboxylic Acid Modified Buried Interface of High‐Performance Perovskite Solar Cells

AbstractThe regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2′‐bipyridyl‐4,4′‐dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb2+) atoms through Lewis acid‐base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO2 and buried perovskite layers. In addition, the electron‐deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO2. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41 % under standard AM 1.5G conditions, along with remarkable environmental stability.

Surface n-Doped Metal Halide Perovskite for Efficient and Stable Solar Cells through Organic Chelation.

Perovskite solar cells (PSCs) have emerged as a leading photovoltaic technology due to their high efficiency and low cost. Even though they have developed rapidly since their inception, with efficiencies of over 26%, inverted PSCs face challenges such as nonradiative recombination and ion migration. Surface treatment, especially the utilization of organic compounds, has improved efficiency and stability by optimizing the perovskite-charge transport layer interface. Herein, we report a facile and effective strategy by introducing 2,2'-bipyridyl to modify the surface of perovskite, achieving a power conversion efficiency of 24.43% with increasing open-circuit voltage and fill factor and good repeatability on multiple devices. We reveal that the 2,2'-bipyridyl molecule can chelate lead ions on the surface of perovskite, effectively suppressing nonradiative recombination. Furthermore, this modification can induce surficial n-doping to refine the energy level alignment, thereby minimizing charge transport losses. Additionally, the device maintained over 92% of the initial efficiency after 1000 h of operation at the maximum power point under continuous illumination. This surface chelation and defect passivation strategy employing 2,2'-bipyridyl offers a promising avenue for exploring the details of potential long-term degradation mechanisms and the development of commercially viable high-performance p-i-n PSCs.

Low-dimensional phase optimization and defect passivation of quasi-2D perovskite to enhance electroluminescence by introducing b-NA

The energy funnel effect holds significant potential for enhancing light-emitting diodes (LEDs) performance in the Quasi-two-dimensional (Quasi-2D) perovskite, which feature a unique multi-quantum well structure. However, random phase distribution and defects within Quasi-2D films pose challenges, leading to inefficient energy transfer and nonradiative recombination, thereby limiting device performance. Here, sodium 2-naphthalene sulfonate (b-NA) is introduced into the Quasi-2D perovskite film to enhance its the optical and electrical properties. The strong interaction between the S = O group and Na+ in b-NA with the perovskite matrix leads to reduced grain size, facilitating agglomeration and densification. This modification decreases the proportion of the low-n phase, enhances thermal stability, and passivates surface defects. Therefore, compared to the control device, the maximum brightness and external quantum efficiency of Quasi-2D perovskite LEDs with the optimal concentration (8b-NA) more than double, and the operational lifetime (T50) of the unpackaged device extends from 70.1 min to 168.5 min.

Functional design and understanding of effective additives for achieving high-quality perovskite films and passivating surface defects

Achieving high-quality perovskite films without surface defects is regarded as a crucial target for the development of durable high-performance perovskite solar cells. Additive engineering is commonly employed to simultaneously control the growth of perovskite crystals and passivate defects. Here, 4-(trifluoromethyl)benzoic anhydride (4-TBA) composed of benzene rings functionalized with carbonyl and trifluoromethyl groups was used as an example additive to study the characteristics of additives used for producing high-quality perovskites and controlling their surface properties. The interaction between 4-TBA and perovskite precursor materials was investigated using density functional theory (DFT) simulations. The electron-rich carbonyl group efficiently passivated the under-coordinated lead-ion defects. Additionally, hydrogen bonding between trifluoromethyl and organic cations prevents the generation of cation vacancies. Because of its intrinsic hydrophobicity, the trifluoromethyl group simultaneously improves the moisture and heat stability of the film. 4-TBA serves as a universal modifier for various perovskite compositions. The power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) based on methylammonium (MA) with 4-TBA was improved from 16.15% to 19.28%. Similarly, the PCE of inverted PSCs based on a cesium formamidinium MA (CsFAMA) perovskite film increased from 20.72% to 23.58%, upon addition of 4-TBA. Furthermore, the moisture and thermal stability of 4-TBA-treated films and devices was significantly enhanced, along with prolonged device performance. Our work provides guidance on selecting the structure and functional groups that are essential for surface defect passivation and the production of high-quality perovskites.

Selective passivation of 2D MoS2 nanosheets surface defects by spontaneous growth of Au nanoparticles for full response-recovery NO2 detection at room temperature

Full recovery at room temperature (RT) is quite challengng for two dimensional transition metal dichalcogenides chemiresistive gas sensors. The main reason for the incomplete recovery is the strong bonding of gas molecules onto sensing layer defects. Here, we show that the recovery rate of MoS2 chemiresistive NO2 sensors can be improved by selective passivation of MoS2 nanosheets (NSs) defects with Au nanoparticles (NPs) via a simple spontaneous reduction method. MoS2 NSs were produced by liquid shear exfoliation. Pristine and Au NPs functionalized MoS2 were characterized using ς-potential, UV–Visible spectroscopy, TEM, SEM, AFM, EDS, XRD, XPS and Raman spectroscopy. The analyses confirm the presence of Au NPs on the edges of MoS2 NSs at defective sites with NP sizes of 1–4 nm and 5–30 nm. Both pristine MoS2 and Au-decorated MoS2 NSs were employed to fabricate NO2 chemiresistive devices. Au-decorated MoS2 sensors showed an improved performance (for 1 ppm NO2, Au-MoS2 sensor exhibited a response of 5.6 % instead of 2.2 % for MoS2 sensor), and gave faster response and better recovery time. Concurrently, the functionalization is independent of the adsorption and desorption of NO2. Most importantly, the functionalization of MoS2 NSs helps to full response-recovery within one hour, without either thermal or UV irradiation treatment.

Oxygen plasma treatment to passivate surface defects for high stability CsPbCl2Br light emitting diodes

Metal halide perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for blue light emission by mixing halides such as bromine (Br) and chlorine (Cl). However, these mixed halide perovskites often suffer from halogen separation under light illumination, leading to spectral shifts and performance degradation. Reducing surface defects in perovskites is critical to preventing ion migration, enhancing film stability, and preventing photo-induced phase separation. In this study, we develop an oxygen plasma treatment strategy to create new perovskite surfaces with lower trap densities by optimizing the plasma power and treatment duration. This treatment dissociates oxygen into ions that form strong Pb–O bonds with uncoordinated lead ions on the perovskite surface, effectively passivating surface defects and prevent ion migration. As a result, the photoluminescence intensity of the CsPbCl2Br film is significantly improved, with no halogen separation observed even after 12 h of continuous 25 W/cm2 laser illumination. Use the optimized thin film, we fabricated all-inorganic Ag/N–Si/CsPbCl2Br/NiO/ITO LEDs that achieved deep blue light emission with high color purity at a 443 nm (full width at half maxima of 18 nm). Notably, these PeLEDs exhibite excellent spectral stability, with only a slight EL peak shift even at a high operational voltage of 7 V. The oxygen plasma treatment demonstrated in this study provides a promising method for reducing surface defects and suppressing phase separation in mixed halides, offering significant potential for developing highly stable deep blue perovskite LED applications.

Efficient Energy Transfer from Quantum Dots to Closely‐Bound Dye Molecules without Spectral Overlap

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD‐dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD‐dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady‐state and time‐resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange‐type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD‐molecule hybrids for a wide range of applications.

Efficient Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules without Spectral Overlap.

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD-dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD-dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady-state and time-resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange-type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD-molecule hybrids for a wide range of applications.

Formation and Passivation of Surface Defects in Lead-Free Tin Halide Perovskites

Formation and Passivation of Surface Defects in Lead-Free Tin Halide Perovskites

Vertically Oriented 2D Perovskite Layer with n = 1 Phase Enables Efficient and Stable Inverted Perovskite Solar Cells.

Surface passivation with 2D perovskites has been reported to be important for high-performance perovskite solar cells (PSCs). However, it is challenging to achieve a controlled growth of 2D perovskites, which typically feature random orientation and various n number. In this paper, we fabricate a 2D layer with a highly ordered orientation and pure n = 1 phase on top of the perovskite film using the organic spacer molecule 7-fluoro-1,2,3,4-tetrahydroisoquinolinehydrochloride (7-FTH). The formed 2D perovskites feature a highly ordered orientation normal to the substrate and a pure n = 1 phase, which efficiently passivates surface defects of the as-prepared perovskite films and improves the energy level alignment between the perovskite film and electron transport layer. Consequently, the modified PSCs achieve a champion power conversion efficiency (PCE) of 24.65% with improved VOC and fill factor. After being stored in an N2 glovebox for 1200 h and kept in ambient air (room temperature and relative humidity of 50-70%) for 840 h, the modified devices retain 93% and 95% of its initial PCE, respectively.

One‐Stone‐For‐Three‐Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells

AbstractThe electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one‐stone‐for‐three‐birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60‐TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60‐TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60‐TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C60‐TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

One-Stone-For-Three-Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells.

The electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C60-TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

Improvement of photoluminescence efficiency and photoelectricity performances of InP quantum dots through the passivation of surface defects

At present, InP quantum dot-sensitized solar cells (QDSSCs) still show moderate power conversion efficiency (PCE), because of charge recombination on the surface defects. Herein, we report a method to reduce the surface defects of InP quantum dots by Ga-doped and ZnS shell coating, which improves the performance of InP QDSSCs. Simultaneous enhancement of photoluminescence (PL) and photo-electricity performance of Ga doped InP (Ga:InP) quantum dots (QDs), Ga:InP/ZnS core/shell QDs were achieved. The maximum PL quantum yield of Ga:InP QDs and Ga:InP/ZnS QDs reached 14.9% and 76%, respectively. The maximum PCE value of Ga:InP and Ga:InP/ZnS QDSSCs reached 3.0% and 4.5% under 1 sun illumination (AM 1.5 G, 100 mW/cm2), respectively. The J-V curve revealed that Ga doping and ZnS shell coating reduced the surface recombination and increased the cell efficiency and stability. These results provided a new approach to obtaining quantum dot materials with high luminescence properties or good solar cell performances.

2,2'-Bipyridyl-4,4'-Dicarboxylic Acid Modified Buried Interface of High-Performance Perovskite Solar Cells.

The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2'-bipyridyl-4,4'-dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb2+) atoms through Lewis acid-base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO2 and buried perovskite layers. In addition, the electron-deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO2. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41 % under standard AM 1.5G conditions, along with remarkable environmental stability.

Research on the Fabrication and X‐Ray Detection Performance of MAPbBr3‐Based 3D/2D Heterojunctions

Perovskite materials, renowned for their high mean atomic number, charge carrier mobility–lifetime product, and X‐ray absorption coefficient, have emerged as exceptional candidates for the fabrication of high‐sensitivity X‐ray detectors. Herein, a BA2PbBr4/MAPbBr3 heterojunction is epitaxially grown, with ion migration effectively suppressed through the passivation of surface defects of the 3D heterojunction. Additionally, the presence of an internal electric field within the heterojunction facilitated the extraction and accumulation of photoinduced charge carriers, further enhancing device sensitivity (5964.05 μC Gy−1 cm−2). The fabricated 2D/3D perovskite heterojunction devices show outstanding self‐driven X‐ray detection performance at 0 V mm−1 bias (1195.5 μC Gy−1 cm−2), surpassing that of α‐Se detectors (20 μC Gy−1 cm−2). The proposed method for the fabrication of self‐driven detectors is relatively simple and is therefore expected to contribute to the commercialization of perovskite‐based X‐ray detectors.

Molecularly tailored bifunctional nano-overlayers for efficient and stable inverted perovskite solar cells

Triple cation perovskite solar cells (PSCs) have made remarkable progress in power conversion efficiency (PCE), which is also related to the interface regulation layers between the active layer and electron transport layer (ETL). The ionic nature of the perovskite lattice has enabled approaches to passivate molecular defects through the interaction of functional groups. Herein, a passivator OXD-7 is introduced as a modified layer to passivate surface defects and accelerate electron transfer. It has been observed that OXD-7 can alleviate the micro-strain of the perovskite thin films through intermolecular bonding, which suppresses the iodide vacancy on the perovskite surface. Additionally, the OXD-7 reduces the surface energy of the perovskite films and inhibits the formation of δ-FAPbI3 on the surface of perovskite film. Consequently, the resulting devices demonstrate improved fill factor and device stability. Under optimal fabrication conditions, triple cation mixed perovskite solar cells with an inverted structure achieve a PCE of 23.83%.