Initial Power Conversion Efficiency Value Research Articles

Enhanced Perovskite Solar Cell Performance via 2-Amino-5-iodobenzoic Acid Passivation.

The intrinsic stability issues of the perovskite materials threaten the efficiency and stability of the devices, and stability has become the main obstacle to industrial applications. Herein, the efficient and facile passivation strategy by 2-amino-5-iodobenzoic acid (AIBA) is proposed. The impact of AIBA on the properties of the perovskite films and device performance is systemically studied. The results show that the trap states are eliminated without affecting the crystal properties of the perovskite grains, leading to the enhanced performance and stability of the perovskite solar cells (PSCs). A high power conversion efficiency (PCE) of 20.23% and lower hysteresis index (HI) of 1.49‰ are achieved, which represent one of the most excellent PCE and HI values for the inverted PSCs based on MAPbI3/[6,6]-Phenyl-C61-Butyric Acid Methyl Ester (PCBM) planar heterojunction structure. Moreover, the UV stability of the perovskite films and the thermal and moisture stability of the devices are also enhanced by the AIBA passivation. The PCE of the device with AIBA can maintain about 83.41% for 600 h (40 RH %) and 64.06% for 100 h (55-70 RH %) of its initial PCE value without any encapsulation, while the control device can maintain only about 72.91 and 45.59% of its initial PCE. Density functional theory calculations are performed to study the origins of enhanced performance. Interestingly, the results show that the surface states induced by AIBA can facilitate the photoexcited charge transfer dynamics and reduce the electron-hole recombination loss. The passivation method developed in this work provides an efficient way to enhance the stability and performance of inverted PSCs.

A Trifluoroethoxyl Functionalized Spiro‐Based Hole‐Transporting Material for Highly Efficient and Stable Perovskite Solar Cells

It is crucial to finely optimize the properties of hole transport materials (HTMs) to improve the performance and stability of perovskite solar cells (PSCs). Herein, a new spiro‐based HTM (Spiro‐4TFETAD) is developed by replacement of partial methoxy groups in Spiro‐OMeTAD with trifluoroethoxy substituents. Spiro‐4TFETAD has lower highest occupied molecular orbital level, higher thermal stability (Tg = 140 °C), hole mobility (2.04 × 10−4 cm2 V−1 s−1), and better hydrophobicity with respect to Spiro‐OMeTAD. The PSCs using Spiro‐4TFETAD achieve a power conversion efficiency of 21.11% and excellent humidity resistance. It maintains an average 83% of their initial power conversion efficiency values even in high relative humidity of 60% without encapsulation and 82% of its initial performance after 100 h continuous illumination at the maximum power point. The superior performance underscores the promising potential of the trifluoroethoxyl molecular design in preparing new HTMs toward highly efficient and stable PSCs.

Defect passivation and interface modification by tetra-n-octadecyl ammonium bromide for efficient and stable inverted perovskite solar cells

Charge recombination loss caused by defects and interfaces in the inverted perovskite solar cells (PSCs) significantly impact cell performance and stability. Here, a kind of quaternary ammonium salt of tetra-n-octadecyl ammonium bromide (TODB) with an symmetrical structure is introduced into inverted PSCs to suppress the charge recombination loss. We have comprehensively studied the impact of TODB on the physical properties of the perovskite films and corresponding the performance of the devices. TODB post-treatment results in defect passivation, the built-in electric field enhancement as well as hydrophobicity improvement in the inverted PSCs, which correspondingly enhance device performance and stability. The highest power conversion efficiency (PCE) reaches 20.36 %, which is one of the highest PCE of the inverted PSCs based on methylammonium lead iodide (MAPbI3)/phenyl-C61-butyric acid methyl ester (PCBM) planar heterojunction. The device with TODB modification can maintain 80 % of its initial PCE value in the air for 384 h, while the control device only maintains about 52 % of its initial PCE under the same exposure conditions. This work presents an efficient strategy to improve the performance and stability of the PSCs by passivating the trap states at the interfaces and increasing the hydrophilicity of the perovskite films.

A study of the effects of a thermally evaporated nanoscale CsBr layer on the optoelectronic properties and stability of formamidinium-rich perovskite solar cells

Incorporation of cesium (Cs) into the perovskite layer has become a good strategy to boost the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, a suitable and scalable method of Cs incorporation in a perovskite film that does not cause a significant increase in the optical bandgap is needed. In this paper, we introduce a thin layer of CsBr into a formamidinium (FA)-rich mixed halide perovskite film using the thermal evaporation technique. The effects of the thickness of the CsBr layer on the microstructural, structural, and optoelectronic properties and surface chemical states of the perovskite film are then studied. The results indicate that the CsBr layer thickness is able to tune the microstructural and optoelectronic properties of the perovskite film. Planar PSCs fabricated with different thicknesses of CsBr layers in the perovskite absorber exhibited different photovoltaic performance characteristics. The CsBr-modified PSC device with a 50 nm layer of CsBr in the perovskite layer showed a better PCE of 16.19% ± 0.17%, which was about 15% higher than that of the control device, and was able to retain nearly 70% of its initial PCE value after 120 days of storage in an unencapsulated state.

Stiffening the Pb-X Framework through a π-Conjugated Small-Molecule Cross-Linker for High-Performance Inorganic CsPbI2Br Perovskite Solar Cells.

Inorganic CsPbI2Br perovskites have witnessed incredible advances as a promising representative for translucent and tandem solar cells, but unfortunately, they are still plagued by serious energy losses and undesired phase instability. Herein, a new type of π-conjugated small molecule of 4-guanidinobenzoic-acid-hydrochloride (4-GBACl) is demonstrated to effectively cross-link the Pb-X framework of perovskites. The strong coordination between 4-GBACl and the [PbX6]4- octahedron of perovskites effectively stiffens the Pb-X framework to suppress the ion migration, thus stabilizing the perovskite phase structure against light and thermal conditions. Apart from the physical barrier for phase instability resulting from the hydrophobic benzene ring at grain boundaries (GBs), guanidinium cations and -COOH and Cl- groups can simultaneously afford the passivation of positively and negatively charged defects at the GBs and surface, including undercoordinated halide species and undercoordinated Pb2+ ions, thereby effectively inhibiting the charge trapping/recombination centers. Two-dimensional confocal-fluorescence mapping images provide a visualized sight into the significantly suppressed nonradiative recombination and the prolonged carrier lifetime. It is suggested that the 4-GBACl additive plays multiple roles in grain cross-linking to regulate crystallization, distinctly reducing the trap-state density, ion migration inhibition, and moisture barrier in CsPbI2Br films. Consequently, the 4-GBACl-treated device exhibits a champion power conversion efficiency (PCE) of 15.59% accompanied with a considerably improved Voc of 1.28 V and maintains 88% of the initial PCE value after 1200 h aging under 20% relative humidity.

Evident Enhancement of Efficiency and Stability in Perovskite Solar Cells with Triphenylamine-Based Macromolecules on the CuSCN Hole-Transporting Layer

The CuSCN-containing perovskite solar cells (PSCs) are presently of great research focus due to the high carrier mobility and well-aligned work function of the CuSCN hole-transporting layer. The improvement of photovoltaic performance and stability is still an important subject in the practical applications of CuSCN-containing PSCs. Herein, a facile approach to improve the efficiency and stability of CuSCN-containing PSCs is developed by spin-coating the triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode, such as linear macromolecule poly-TPD and branched macromolecule CRA-TPA. The maximum power conversion efficiency (PCE) of CuSCN-containing PSCs is increased by linear triphenylamine-based macromolecule poly-TPD to 10.36% while the PCE value of CuSCN-containing PSCs, being modified by branched triphenylamine-based macromolecule CRA-TPA, reaches up to 11.97%. Evidently, the PCE values are nearly two times higher than 5.95% of CuSCN-containing control device. The photovoltaic improvement of macromolecule-modified CuSCN-containing PSCs is mainly caused by the strong hole-transporting capacity of triphenylamine-based macromolecules inducing the reduction of charge recombination, which is derived from the reduced potential barrier of hole transportation including the flatness and coverage improvement in the triphenylamine-based macromolecular functional layer. In addition, the stability of macromolecule-modified CuSCN-containing PSCs is significantly improved due to the protection of triphenylamine-based macromolecular layer on the perovskite film, so that the unencapsulated macromolecule-modified CuSCN-containing PSC device can keep over 70–80% of initial PCE value after 20-day exposure under ambient environment (relative humidity (RH) = 50%, 25°C). This work provides a facile approach to enhance the efficiency and stability of CuSCN-containing PSCs through the modification of triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode.

Tailored conductive fullerenes-based passivator for efficient and stable inverted perovskite solar cells

Interfacial defects result in a limitation to the development of highly efficient and stable perovskite solar cells. The passivation of these defects by adopting various interfacial defects passivation agents is a common method for boosting device performance. However, most existing interfacial defects passivation agents form poorly conductive aggregates at the perovskite interface with the electron transport layer (ETL), hindering the transport of charge carriers. In addition, the electron mobility of passivation agents is an important factor that affects the electron communication between the adjacent layers. Herein, a fullerene-based molecular passivator, [60]fullerene-4-(1-(4-(tert-butyl)phenyl)pyrrolidin-2-yl)benzenaminium (C60-tBu-I), is designed and synthesized. This novel n-doping fullerene ammonium iodide is developed as an interfacial modification agent to accelerate charge transport from the perovskite active layer into the ETL while hindering the nonradiative charge carrier recombination. Hence, compared with the control devices (15.66%), C60-tBu-I-modified device presents a higher efficiency of 17.75%. More importantly, the tert-butyl group dramatically enhances the resistance of perovskite films to water molecular. As a result, C60-tBu-I-modified devices exhibit excellent long-term stability, remaining at more than 87% of the initial power conversion efficiency value after storage for 500 h.

Ultra-thin and high transparent Cu2ZnSnSe4/NiOx double-layered inorganic hole-transporting layer for inverted structure CH3NH3PbI3 perovskite solar cells

Inorganic hole transporting layer (HTL) plays the most important role to fabrication of low cost and stable in perovskite solar cells. Herein, we present low cost highly transparent and ultra-thin sputtered Cu2ZnSnSe4 (CZTSe) combined with solution-processed NiOx films as a double-layered inorganic HTL applied in inverted CH3NH3PbI3 perovskite solar cells, which is beneficial to enhance hole extraction and suppress electron transport. Sputtered CZTSe films have high transmittance (> 85%), high hole mobility (15.1 cm2 v−1 s−1), low resistivity (0.33 Ω-cm), earth-abundant elemental constituents, and non-toxic properties, which is one of the promising p-type inorganic hole-transporting material. An obvious enhancement of open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of a 600 °C-annealed-CZTSe/NiOx double-layered HTL based inverted perovskite solar cell was observed, and final Voc, Jsc, FF, and PCE of 1.03 V, 17.9 mA cm−2, 73%, and 13.46% were achieved, respectively. Importantly, the ultra-thin CZTSe/NiOx double-layer HTL makes the perovskite solar cell exhibit improved stability, of which this device remains 73% of the initial PCE value after 350 h′ storage in the nitrogen-filled glove box.

Enhanced Efficiency and Mechanical Robustness of Flexible Perovskite Solar Cells by Using HPbI3 Additive

High efficiency and mechanical stability are in great demand for commercial applications of the flexible perovskite solar cells (PSCs) in portable and wearable electronics. Herein, power conversion efficiency (PCE) and mechanical robustness of the methylammonium (MA)‐free flexible PSCs are simultaneously enhanced by incorporating a HPbI3 additive with optimal content in the perovskite precursor solution. The HPbI3 additive facilitates an improved morphology and crystallinity, as well as a decreased work function of the perovskite films, leading to improved device performance. As a result, PCEs of 20.1% and 18.74% are obtained for the rigid and flexible PSCs, respectively, which are among the best results for inverted MA‐free PSCs. The flexible PSCs maintain 95% and 70% of the initial PCE value after 1000 and 5000 bending cycles, respectively, at a bending radius of 4 mm. The current result reveals that using the HPbI3 additive is a universal strategy to enhance performance of the flexible PSCs effectively and promote the development of the perovskite‐based photovoltaics.

Influence of Inorganic NiOx Hole Transport Layer on the Growth of CsBi3I10 Perovskite Films for Photovoltaic Applications

AbstractLead (Pb)‐free bismuth (Bi) halide perovskites are promising alternatives to Pb‐based ones for the fabrication of perovskite solar cells (PSCs). However, the energy‐level mismatch at the interface between Bi perovskite (CsBi3I10;CBI) and the charge carrier transport layer limits the performance of the PSCs. Here, spray pyrolysis processed nickel oxide (sp‐NiOx) is reported as a hole transport layer (HTL) for CBI‐based inverted planar PSCs. Influence of inorganic NiOx HTL is systematically studied on the structural and morphological properties of the CBI perovskite layer growth. The CBI perovskite deposited on top of the sp‐NiOx exhibits improved crystallinity. The fabricated sp‐NiOx layer also exhibits favorable optical and electrical properties. The deep valence band (−5.4 eV) of the sp‐NiOx HTL is able to reduce the energy‐level mismatch up to 0.3 eV at the interface with the CBI layer. The PSCs fabricated with sp‐NiOx as HTL also exhibits a power conversion efficiency (PCE) of 0.72%, with a short‐circuit current density of 2.89 mA cm−2. The sp‐NiOx HTL based device maintains 85% of its initial PCE value even after 100 h of light soaking. This work highlights the importance of having a suitable HTL along with appropriate interface engineering for the Bi halide photovoltaic devices.

Assembly of Fe(III)‐Grafted Metal–Organic Complexes as p‐Type Dopants for Efficient and Stable Perovskite Solar Cells

Realizing the rapid/controllable oxidation of 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) under an inert atmosphere, reducing the J–V hysteresis and enhancing the air stability of devices is extremely significant to fabricate high‐performance perovskite solar cells (PSCs). Herein, the Fe(III) ion grafted metal–organic complexes (Fe(III) ⊂ MOCs) are assembled and used as the p‐type dopants of hole transport layers (HTLs) to prepare efficient and stable PSCs. Consequently, the optimal Fe(III) ⊂ In‐2‐bpydc‐doped device presents a significantly enhanced power conversion efficiency (PCE) of 20.46%, benefitting from the improved hole extraction and weakened carrier recombination at the interface between HTLs and perovskite films. More importantly, the modified device possesses a reduced J–V hysteresis index (HI) of 0.094, and can maintain nearly 90% of its initial PCE value after being exposed to the air at ≈25 °C and relative humidity (RH) of ≈35% for 4 weeks, which is attributed to the restrained detrimental penetration behavior by the MOC carrier part of dopants. This work is of important guiding significance for the application of MOC materials in photovoltaic fields.

Enhancing efficiency and decreasing photocatalytic degradation of perovskite solar cells using a hydrophobic copper-modified titania electron transport layer

The electron transport layer (ETL) plays a pivotal role in obtaining perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Titanium dioxide is a widely used ETL, however it suffers from low electron mobility, poor conductivity and may act as a photocatalyst of chemical reactions leading to degradation of the perovskite. Herein, copper cations employed to modify the titania ETL of PSCs, mitigate the photocatalytic action of the compact layer, increase its conductivity and electron mobility, adjust favorably the energy levels, improve the ETL/perovskite interface, thus enhance perovskite’s light absorption and provoke passivation of the perovskite surface trap states. The investigation of structural and surface chemistry properties revealed the uniform distribution of Cu1+ in TiO2 and confirmed the determining role of copper in the fast extraction of the photogenerated charge carriers to the adjacent electrode. As a result, the champion planar PSCs based on the hydrophobic Cu-TiO2 ETL showed a 18.15 % PCE outperforming the reference devices (based on pristine TiO2 ETL) which showed a PCE equal to 15.78 %. The results followed the same trend also in the case of mesoporous PSCs, proving the universality of our approach. Finally, aging tests confirmed that the copper-modified devices showed higher stability in comparison with the non-modified ones retaining the 53 % of the initial PCE value after 51 days of storage in relative humidity (RH = 25 %) and dark conditions. Photostability experiments proved that the Cu-TiO2 based devices showed remarkable robustness and retained approximately 91 % of their initial PCE, even after 5 h under continuous UV stress. These results are associated with the suppression of the photocatalytic activity of the ETL and open new perspectives for improving the performance of TiO2-based PSCs.

Gold nanoparticle decorated carbon nanotube nanocomposite for dye-sensitized solar cell performance and stability enhancement

• AuNP/MWCNT inlaid mesoporous TiO 2 films are fabricated as photoanodes for DSSCs. • An enhancement of ~31% in PCE is achieved by using AuNP/MWCNT nanocomposite. • AuNP/MWCNT increases the PCE of the DSSC with a thin anode. • The developed nanocomposite is able to significantly improve the long-term stability of DSSCs. Improving the conversion efficiency of dye-sensitized solar cells (DSSCs) requires enhancing the photogeneration of charge carriers as well as facilitating their transport to electrodes before charge recombination or quenching can occur. Here we describe a simple, fast and large-area scalable procedure for the preparation of a nanocomposite made of functional gold nanoparticles (AuNPs) and multiwall carbon nanotubes (MWCNTs) to improve the performance of DSSCs. We fabricated AuNP/MWCNT inlaid mesoporous TiO 2 films as photoanodes in DSSCs, to improve crucial factors including light absorption, charge-carrier generation, collection and transport. By using a AuNP/MWCNT nanocomposite directly inlaid in TiO 2 as the working electrode, a power conversion efficiency (PCE) of 6.61% and short-circuit photocurrent density ( J sc ) of 12.26 mA cm −2 were obtained, representing an enhancement of ~31% in PCE and ~19% in J sc compared to a control cell based on TiO 2 alone. In addition, DSSCs based on the TiO 2 /AuNP/MWCNT photoanode remained remarkably stable compared with the control device, retaining 92% of the initial PCE value after ten days of continuous illumination.

Efficient, Hysteresis‐Free, and Flexible Inverted Perovskite Solar Cells Using All‐Vacuum Processing

The fabrication of efficient perovskite solar cells (PSCs) using all‐vacuum processing is still challenging due to the limitations in the vacuum deposition of the hole transporting layer (HTL). Herein, inverted PSCs using copper (II) phthalocyanine (CuPC) as an ideal alternative HTL for vacuum processing are fabricated. After proper optimization, a PSC with a power conversion efficiency (PCE) of 20.3% is achieved, which is much better than the PCEs (16.8%) of devices with solution‐based CuPC. As it takes a long time to dissolve CuPC in the solution‐based device, the evaporation approach has better advantage in terms of fast processing. In addition, the device with the evaporated CuPC HTL indicates an excellent operational stability, showing only 9% PCE loss under continuous illumination after 100 h, better than its counterpart device. Interestingly, the device shows negligible hysteresis. As all fabrication processes are conducted at low temperatures, flexible PSCs are also fabricated on ITO/PET substrates and a PCE of 18.68% is obtained. After 200 bending cycles, the flexible device retains 87.5% of its initial PCE value, indicating its great flexibility. Herein, the role of a suitable HTL for the fabrication of all‐vacuum‐processing PSCs with great efficiency and stability is highlighted.

Stable and Highly Flexible Perovskite Solar Cells with Power Conversion Efficiency Approaching 20% by Elastic Grain Boundary Encapsulation

Here, we show that flexible perovskite solar cells (PSCs) with high operational stability and power conversion efficiency (PCE) approaching 20% were achieved by elastic grain boundary (GB) encapsul...

HClO4-assisted fabrication of SnO2/C60 bilayer electron-transport materials for all air-processed efficient and stable inverted planar perovskite solar cells

In inverted planar perovskite solar cells (PSCs), fullerene (C60) and its derivatives are widely utilized as electron-transport layer (ETL) materials, however, possess some drawbacks such as low electron mobility, interfacial degradation, and relatively inferior stability. In this work, we develop a facile thermal annealing-free hydrothermal route to synthesize high-crystalline SnO2 nanocrystals through controlling the crystallization process with HClO4. An interlayer of SnO2 nanocrystals is inserted between C60 ETL and Ag electrode. The SnO2 interlayer can not only serve as an ETL to help improve electron extraction and transport but also act as a passivation/barrier layer to prevent oxygen and moisture ingress and ion migration. Based on the p-i-n structure of fluorine-doped tin oxide (FTO)/NiOx/MAPbI3/C60/SnO2/Ag, the power conversion efficiency (PCE) of the champion device is up to 16.36% with almost negligible hysteresis. The unencapsulated inverted PSCs retain more than 80% of its initial PCE value after storage in atmosphere for 90 days (>2100 h), and degrade only about 20% its initial efficiency after 41 h under heating at 85 °C. More important, all the preparation processes are performed under ambient conditions. Our work provides a viable strategy for assembling highly efficient and stable inverted PSCs in the air.

Constructing m-TiO2/a-WOx hybrid electron transport layer to boost interfacial charge transfer for efficient perovskite solar cells

Recently, the rapid improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) with surprising and efficient PSCs is considered to be the most promising alternative to the next generation photovoltaic. In PSCs, the interfacial charge transfers between perovskite and electron transporting layers (ETLs) play an important role in enhancing the PCE, hysteresis, and stability. Here, an amorphous WOx (a-WOx) interlayer is interposed between the perovskite layer and mesoporous TiO2 (m-TiO2) layer to boost the hetero-interface charge transport. The room-temperature processed a-WOx has a wide bandgap and high electron mobility, which is capable of efficiently transporting photo-generated electrons, thereby reducing interfacial charge accumulation in the PSCs. Besides, we first found that the m-TiO2/a-WOx hybrid ETLs have better non-wettability, which subsequently improves the crystallization of the perovskite films by promoting the grain boundary mobility. Consequently, under optimized MAPbI3 solar cells having m-TiO2/a-WOx hybrid ETLs exhibits the highest Voc of 1.16 V and the PCE of 20.98%. Stability tests indicate that the PCE value based on the m-TiO2/a-WOx device remains more than 91% after exposure to 45% humidity for 30 days in the dark at room temperature, much higher than the m-TiO2 based cell, which retains about 70% of the initial PCE value.

Efficient Bidentate Molecules Passivation Strategy for High‐Performance and Stable Inorganic CsPbI2Br Perovskite Solar Cells

All inorganic mixed‐halide CsPbI2Br perovskites with suitable bandgap and superior thermal durability have ignited rising interests in the field of perovskite solar cells (PSCs). However, the serious energy losses derived from deleterious trap‐assisted defects–induced notorious nonradiative recombination and inferior moisture durability are still the primary hindrance on the way to develop high‐performance CsPbI2Br PSCs. Herein, a novel passivation strategy is presented by introducing dual‐functionalized bidentate molecule 2‐(2′‐thienyl)pyridine (2‐ThPy) to modulate perovskite crystallization and passivate halogen vacancy defects. Compared with monodentate counterparts, 2‐ThPy can anchor Pb2+ sites via S and N atomic bonding simultaneously, and the synthesized CsPbI2Br films exhibit enlarged grain size, show advantages to passivate defect states, and dramatically reduce trap density, thereby lessening the detrimental carrier recombination. Consequently, a champion power conversion efficiency (PCE) of 12.69% with negligible hysteresis is delivered for the fabricated CsPbI2Br PSCs treated with 2‐ThPy. Moreover, the moisture stability of CsPbI2Br PSCs with 2‐ThPy is also greatly enhanced, and the device without encapsulation retains 92% of initial PCE value after 30 days aging under 25 °C and 40% relative humidity in ambient environment. The bidentate molecules passivation strategy paves a promising avenue to implement efficient and stable inorganic PSCs.

The role of hafnium acetylacetonate buffer layer on the performance of lead halide perovskite solar cells derived from dehydrated lead acetate as Pb source

In this research, we demonstrated the use of hafnium acetylacetonate (Hfaca) dissolved in ethanol as a buffer layer for perovskite solar cells from non-halide Pb (dehydrated lead acetate) source material. The inverted p-i-n planar heterojunction structure was employed in this work. A one step spin-coating method was used in depositing the perovskite solution before thermal annealing at 90 °C for 5 min to form the perovskite film. Hfaca has been previously used as a buffer layer, but the optimal concentration has not been reported. The optimum concentration of Hfaca was found to be 1.0 mg/ml, resulting in a power conversion efficiency (PCE) of 12.23% corresponding to more than 30% improvement when compared to the control device (phenyl-C61-butyric acid methyl ester/Ag) without Hfaca, which has a PCE of 8.89%. Hfaca as a buffer layer leads to superior stability, retaining about 90% of its original PCE values after 15 days of storage in a glove box, compared to the control device, which retains 70% of the initial PCE value under the same storage.

Dendritic PAMAM polymers for strong perovskite intergranular interaction enhancing power conversion efficiency and stability of perovskite solar cells

The modification of perovskite intergranular perovskite/perovskite interface plays a critical role for power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). In this work, polyamidoamine (PAMAM) dendrimers are utilized as the dendritic crystallization framework templating the perovskite-crystallizing process. The interactions at the perovskite intergranular interface are considerably strengthened at an ambient environment with dendritic PAMAMs crosslinking the perovskite grains. Consequently, the perovskite morphology is remarkably improved by suppressing the grain/grain-aggregate boundaries for the pinhole removal, which produces a compact, uniform and non-pinhole perovskite film. Finally, the strengthened interfacial interactions dramatically enhance the PCE value of unencapsulated PSCs about 42.6% at an ambient condition. Besides, the unencapsulated PAMAM-modified device can keep 73% of initial PCE value in 400 h while the control device decays to 5% of initial PCE value in 50 h. These results reveal that dendritic polymers might remarkably improve the PCE value and the stability of PSCs. This work provides a new molecular design guideline to effectively regulate the perovskite intergranular interfacial interactions.