JIALINGBO

High‐efficiency solution‐processed hybrid tandem photovoltaic devices, employing inorganic perovskite and organic bulk‐heterojunction as the photoactive layers, are demonstrated. A PCE of 18.04% in the hybrid tandem device is achieved, which is significantly higher than the comparable single‐junction devices, owing to a near‐optimal absorption spectral match.

Abstract

Although the power conversion efficiency (PCE) of inorganic perovskite‐based solar cells (PSCs) is considerably less than that of organic‐inorganic hybrid PSCs due to their wider bandgap, inorganic perovskites are great candidates for the front cell in tandem devices. Herein, the low‐temperature solution‐processed two‐terminal hybrid tandem solar cell devices based on spectrally matched inorganic perovskite and organic bulk heterojunction (BHJ) are demonstrated. By matching optical properties of front and back cells using CsPbI₂Br and PTB7‐Th:IEICO‐4F BHJ as the active materials, a remarkably enhanced stabilized PCE (18.04%) in the hybrid tandem device as compared to that of the single‐junction device (9.20% for CsPbI₂Br and 10.45% for PTB7‐Th:IEICO‐4F) is achieved. Notably, the PCE of the hybrid tandem device is thus far the highest PCE among the reported tandem devices based on perovskite and organic material. Moreover, the long‐term stability of inorganic perovskite devices under humid conditions is improved in the hybrid tandem device due to the hydrophobicity of the PTB7‐Th:IEICO‐4F back cell. In addition, the potential promise of this type of hybrid tandem device is calculated, where a PCE of as much as ≈28% is possible by improving the external quantum efficiency and reducing energy loss in the sub‐cells.

A homochiral molecular ferroelectric was incorporated into a perovskite film to enlarge the built‐in electric field of the perovskite solar cell, thereby facilitating charge separation and transportation for improved device performance. In their Research Article (DOI: https://doi.org/10.1002/anie.20200849410.1002/anie.202008494), J. Zhao, W.‐Q. Liao, G.‐F. Zou, and co‐workers show that the molecular ferroelectric component of the perovskite solar cell passivates the defects in the perovskite active layers, reducing nonradiative recombination.

The commercially available pyridinedicarboxylic acid (PDA) molecule with one pyridine and two carboxylic acid groups is used as a passivating agent to cure the defects at both the surfaces and grain boundaries of MAPbI₃ perovskites. A champion power conversion efficiency (PCE) approaching 19% with optimized long‐term stability and thermal stability is achieved in PDA‐passivated perovskite solar cells (PSCs).

Electronic defects and grain boundaries of perovskite films will significantly deteriorate both the efficiency and the stability of perovskite solar cells (PSCs), and various methods aimed to reduce these defects are proposed. Herein, an organic solid molecule of pyridinedicarboxylic acid (PDA) with one pyridine and two carboxylic acid groups is used as a passivating agent to cure the defects by regulating the perovskite microstructures in a multiple manner. The defects located at both the surfaces and grain boundaries of polycrystalline MAPbI₃ perovskites are simultaneously passivated through the multiple coordination effects between the used functional groups and uncoordinated Pb²⁺, regardless of the substitution sites of the carboxylic acid and pyridine. Impressively, the PDA‐passivated inverted PSCs achieve remarkably enhanced power conversion efficiencies (PCEs) from 16.43% to nearly 19% and maintain over 90% of its original PCE after 1300 h under an inert environment. These findings indicate that the commercially available PDA molecule emerges as an efficient passivating agent of perovskite defects capable of stimulating the combined effects of the multiple functional groups, which is highly promising for the practical applications of PSCs with both high efficiency and good stability.

A homochiral molecular ferroelectric was incorporated into a perovskite film to enlarge the built‐in electric field of the perovskite solar cell, thereby facilitating charge separation and transportation for improved device performance. In their Research Article on https://doi.org/10.1002/anie.202008494page 19974, J. Zhao, W.‐Q. Liao, G.‐F. Zou, and co‐workers show that the molecular ferroelectric component of the perovskite solar cell passivates the defects in the perovskite active layers, reducing nonradiative recombination.

Nature Nanotechnology, Published online: 21 September 2020; doi:10.1038/s41565-020-0765-7

The emerging metal halide perovskite arrays are promising components for next‐generation optoelectronic devices. Methods for the construction of perovskite arrays, including template‐assisted growth, substrate‐assisted growth, capillary force‐assisted growth, and direct patterning technologies, are summarized. Various applications of perovskite arrays in integrated optoelectronics are introduced. The challenges and perspectives related to perovskite arrays are discussed.

Abstract

Inorganic semiconductor arrays revolutionize many areas of electronics, optoelectronics with the properties of multifunctionality and large‐scale integration. Metal halide perovskites are emerging as candidates for next‐generation optoelectronic devices due to their excellent optoelectronic properties, ease of processing, and compatibility with flexible substrates. To date, a series of patterning technologies have been applied to perovskites to realize array configurations and nano/microstructured surfaces to further improve device performances. Herein, various construction methods for perovskite crystal or thin film arrays are summarized. The optoelectronic applications of the perovskite arrays are also discussed, in particular, for photodetectors, light‐emitting diodes, lasers, and nanogratings.

Further improvement and stabilization of perovskite solar cell (PSC) performance are essential to achieve the commercial viability of next-generation photovoltaics. Considering the benefits of fluorination to conjugated materials for energy levels, hydrophobicity, and noncovalent interactions, two fluorinated isomeric analogs of the well-known hole-transporting material (HTM) Spiro-OMeTAD are developed and used as HTMs in PSCs. The structure–property relationship induced by constitutional isomerism is investigated through experimental, atomistic, and theoretical analyses, and the fabricated PSCs feature high efficiency up to 24.82% (certified at 24.64% with 0.3-volt voltage loss), along with long-term stability in wet conditions without encapsulation (87% efficiency retention after 500 hours). We also achieve an efficiency of 22.31% in the large-area cell.

An interfacial layer of triphenylamine–polystyrene blend is used between the perovskite layer and charge‐transporting layer to concurrently suppress energy loss and improve device stability. The energy loss is reduced from 0.49 to 0.35 eV, along with a large open‐circuit voltage of 1.18 V and a high power conversion efficiency of 22.1% in air‐stable perovskite solar cells.

Energy loss induced by nonradiative recombinations plays a critical role in determining power conversion efficiencies in perovskite solar cells, whereas device stability impacts their long‐time reliability in the ambient environment. It is an important challenge to suppress energy loss and improve device stability simultaneously. Herein, an interfacial layer of triphenylamine (TPA):polystyrene (PS) blend coated on the hybrid perovskite layer to concurrently suppress energy loss and improve device stability is reported. The energy loss is suppressed from 0.49 to 0.35 eV by passivating surface defects in hybrid perovskites via Lewis acid–base interactions with the combination of electron‐donating aromatic nucleus in PS and tertiary amine in TPA, leading to perovskite solar cells with a high open‐circuit voltage of 1.18 V, a fill factor of about 80%, and a power conversion efficiency of 22.1%. Meanwhile, the device stability in the ambient environment is improved significantly by the TPA:PS blend due to its superior hydrophobicity which is suggested by its high contact angle of 91.1° as compared to 64.0° for the pristine perovskite film. Herein, an efficient interfacial engineering approach with the TPA:PS blend to suppress energy loss and improve device stability simultaneously towards realistic applications is demonstrated.

A coherent interface of PMA₂PbI₄ and FAPbI₃ induces epitaxial growth of α‐FAPbI₃. Facilitated formation of α‐FAPbI₃ at low temperature results in minimal structural disorder and enhanced charge‐carrier transport properties. A perovskite solar cell based on PMA₂PbI₄ and Cs_0.02FA_0.98PbI₃ exhibits an efficiency of 21.25% and stabilized efficiency of 19.95%.

Abstract

Low dimensional (LD) perovskite materials generally exhibit superior chemical stability against ambient moisture and thermal stress than that of 3D perovskites. Recently, LD perovskite has been used as a passivation layer on the surface of 3D perovskite grains. Although various LD perovskites have been developed focusing on their hydrophobicity, the impact of crystal structure of LD perovskite on the photovoltaic performance of perovskite solar cell (PSC) is still uncertain. In this work, the effects of the structural characteristics of LD perovskites on the crystal formation of formamidinium lead triiodide (α‐FAPbI₃) and on the optoelectrical properties of PSCs are elucidated. The phase‐transformation kinetics of FAPbI₃ mixed with LD perovskites is studied using the Johnson–Mehl–Avrami–Kolmogorov model. It is found that the arrangement of PbI₆ octahedra in the LD perovskite changes the rate of α‐FAPbI₃ formation. Facilitated nucleation of α‐FAPbI₃ at the LD/FAPbI₃ interface results in minimal structural disorder and prolonged charge‐carrier lifetimes. As a result, the PSC with the optimized LD perovskite structure exhibits a power conversion efficiency of 21.25% from a reverse current–voltage scan, and stabilized efficiency of 19.95% with excellent ambient stability without being encapsulated.

A biological polymer is employed to regulate the arrangement of SnO₂ nanocrystals on a substrate and induce vertical crystal growth of a perovskite layer on top. The enhanced interface contact between the electron‐transport layer and the perovskite layer significantly contributes to the improvement of efficiency and stability of derived planar perovskite solar cells.

Abstract

Perovskite solar cells (PSCs) have rapidly developed and achieved power conversion efficiencies of over 20% with diverse technical routes. Particularly, planar‐structured PSCs can be fabricated with low‐temperature (≤150 °C) solution‐based processes, which is energy efficient and compatible with flexible substrates. Here, the efficiency and stability of planar PSCs are enhanced by improving the interface contact between the SnO₂ electron‐transport layer (ETL) and the perovskite layer. A biological polymer (heparin potassium, HP) is introduced to regulate the arrangement of SnO₂ nanocrystals, and induce vertically aligned crystal growth of perovskites on top. Correspondingly, SnO₂–HP‐based devices can demonstrate an average efficiency of 23.03% on rigid substrates with enhanced open‐circuit voltage (V _OC) of 1.162 V and high reproducibility. Attributed to the strengthened interface binding, the devices obtain high operational stability, retaining 97% of their initial performance (power conversion efficiency, PCE > 22%) after 1000 h operation at their maximum power point under 1 sun illumination. Besides, the HP‐modified SnO₂ ETL exhibits promising potential for application in flexible and large‐area devices.

Organic‐inorganic hybrid perovskite materials have emerged as promising photovoltaic candidates. Herein, a supramolecular complex [(C₈H₁₇)₄N]₄[SiW₁₂O₄₀] is synthesized and introduced into SnO₂ to produce a mutifunctionalized electron transport layer (ETL). Suppressed trap state density and improved band alignment are attained in modified perovskite solar cells. Devices with [(C₈H₁₇)₄N]₄[SiW₁₂O₄₀] show a champion efficiency of 22.84% and stable performance under irradiation.

Recently, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been developed to exceed 25%, and charge transport layer optimization is a promising strategy for further efficiency improvement in PSCs. Herein, a supramolecular complex [(C₈H₁₇)₄N]₄[SiW₁₂O₄₀] (TASiW‐12) is synthesized and its doped form in SnO₂ (hereafter S‐SnO₂) is used as a charge transport layer (electron transport layer, ETL). This study demonstrates that S‐SnO₂ introduction is a practical and effective way to improve the bulk ETL and those of the ETL/perovskite interface. S‐SnO₂ leads to improved band alignment, suppressed trap‐assisted charge recombination, and enhanced electron mobility. In addition, an enhanced open‐circuit voltage (V _oc) of 1.16 V and an efficiency of 22.8% are successfully achieved in n–i–p planar PSCs. Meanwhile, S‐SnO₂ acts as a crucial agent to reduce charge accumulation at the S‐SnO₂/perovskite interface. The device possesses superior stability for 3072 h with only a 5.65% loss of the initial PCE. These results indicate that high‐efficiency PSCs can be easily attained by introducing a TASiW‐12‐doped ETL with integrated functions.

Pinhole‐free perovskite films with large grains are fabricated in ambient air by a spinning–bathing–spinning method. The effects of moisture on the formation of I‐dominant grain and Cl‐enriched boundaries and surfaces in the perovskite films are revealed, which enable the air‐processed perovskite solar cells with a high efficiency of more than 20%.

Metallic halide perovskite films are usually fabricated in inert environment due to their high sensitivity to moisture and oxygen. However, the fabrication process in the strictly controlled environment is not economical for mass production. Therefore, the fabrication of high‐quality perovskite films in ambient air is more practical for optoelectronic devices. Herein, a spinning–bathing–spinning (SBS) method is demonstrated to deposit pinhole‐free perovskite films with large grains in ambient air for solar cells. The effect of moisture on the rapid crystallization and grain coarsening can be suppressed using this SBS method. Furthermore, the moisture is found to encourage the halogen separation in the perovskite films when using PbI₂–PbCl₂ as the lead halide precursor, resulting in the formation of I‐dominant perovskite grains and Cl‐enriched boundaries and surface in the films. The Cl‐enriched grain boundaries and film surface, which mainly originate from the confined methylammonium chloride (MACl), can passivate defects and prevent further damage from moisture and oxygen. This spontaneous inner‐to‐outside passivation enables the air‐processed perovskite solar cells with the high power conversion efficiencies of more than 20% and improved stability.

Sodium dodecyl benzene sulfonate (SDBS) is used as a multifunctional chemical additive for efficient and stable planar fully air‐processed perovskite solar cells (PSCs). The introduction of SDBS can promote the preferential growth of crystal orientation, reduce defects, inhibit the migration of iodide ions, enhance the built‐in potential, and improve the water resistance of perovskite films.

The device performance of organic–inorganic hybrid halide perovskite solar cells (PSCs) is highly dependent on the quality of perovskite layer. Herein, a multifunctional chemical additive strategy is reported to simultaneously improve the efficiency and stability of fully air‐processed PSCs. The planner methylammonium lead trihalide (MAPbI₃)‐based PSCs incorporating sodium dodecyl benzene sulfonate (SDBS) exhibit a champion power conversion efficiency (PCE) of 19.20% and negligible hysteresis, which is one of the top efficiencies of MAPbI₃‐based PSCs made in air. The increased efficiency is due to the reduction of defects and inhibition of ion migration in the perovskite films. Furthermore, the enhancement of device performance and stability can also be ascribed to highly preferred and efficient perovskite crystals protecting the perovskite films from humidity. The corresponding unencapsulated device retains 92.34% of its initial efficiency after 90 days (>2100 h) storage in air and maintains 85.20% of its original PCE after being exposed to 85 °C for 27 h. The results indicate that SDBS is a promising chemical additive to enhance the performance of air‐processed PSCs for future applications.

This article reports the interfacial modification of compact TiO₂ ETL with Au NPs functionalized with fully conjugated fullerene C₆₀ derivative. This interlayer facilitates charge transfer and reduces charge carrier recombination pathways at interfaces. Consequently, the performance and stability of the modified devices are improved as compared to the reference devices.

Abstract

Titanium dioxide (TiO₂) is an extensively used electron transporting layer (ETL) in n–i–p perovskite solar cells (PSCs). Although, TiO₂ ETL experiences the high surface defect together with low electron extraction ability, which causes severe energy loss and poor stability in the PSC. In this study, a new intermediate layer consisting of gold nanoparticles functionalized with fully conjugated fullerene C₆₀ derivative (C₆₀‐BCT@Au NPs) that enhances the interfacial contact at ETL/perovskite interface leading to a perovskite film with improved crystallinity and morphology is reported. Moreover, the studies demonstrate that the interface modification of the TiO₂ ETL with C₆₀‐BCT@Au NPs substantially improves the charge extraction efficiency from the perovskite layer and suppresses charge recombination processes. Consequently, the resulting device yields a champion efficiency of 19.08% as well as devaluation in hysteresis. In addition, the unencapsulated PSCs with c‐TiO₂/C₆₀‐BCT@Au NPs ETL retain 83% and 90% of their original PCEs after 500 h storage in air and exposure to continuous UV illumination for 200 h, respectively. This study provides an effective method to address the electron transporting issues between perovskite and c‐TiO₂ ETL for developing stable and efficient PSCs.

In article number https://doi.org/10.1002/aenm.2020016102001610, Zonghao Liu, Liyuan Han, Wei Chen and co‐workers, review the stability improvement strategy of perovskite solar cells from the view point of barrier designs. The barriers can address adverse issues like product volatilization, ion diffusion, electrode corrosion, and fight off the harmful influence of external stresses including sunlight, heat, H₂O/O₂, electric bias, etc.

Solution‐processed fullerene derivative, [6,6]‐phenyl‐C61 butyric acid n‐hexyl ester, is reported as an effective electron transport material in perovskite solar cells. It allows smooth capping of the perovskite surface, resulting in high efficiencies, reaching 18.4% for large‐area, flexible devices. Furthermore, compared to other fullerenes, it shows reduced recombination losses at the interface with perovskite and facile scalability with the ink‐jet printing technique.

Abstract

Metal halide perovskites have raised huge excitement in the field of emerging photovoltaic technologies. The possibility of fabricating perovskite solar cells (PSCs) on lightweight, flexible substrates, with facile processing methods, provides very attractive commercial possibilities. Nevertheless, efficiency values for flexible devices reported in the literature typically fall short in comparison to rigid, glass‐based architectures. Here, a solution‐processable fullerene derivative, [6,6]‐phenyl‐C61 butyric acid n‐hexyl ester (PCBC6), is reported as a highly efficient alternative to the commonly used n‐type materials in perovskite solar cells. The cells with the PCBC6 layer deliver a power conversion efficiency of 18.4%, fabricated on a polymer foil, with an active area of 1 cm². Compared to the phenyl‐C61‐butyric acid methyl ester benchmark, significantly enhanced photovoltaic performance is obtained, which is primarily attributed to the improved layer morphology. It results in a better charge extraction and reduced nonradiative recombination at the perovskite/electron transporting material interface. Solution‐processed PCBC6 films are uniform, smooth and displayed conformal capping of perovskite layer. Additionally, a scalable processing of PCBC6 layers is demonstrated with an ink‐jet printing technique, producing flexible PSCs with efficiencies exceeding 17%, which highlights the prospects of using this material in an industrial process.

Perovskite Solar Cells

In article number 2000197, Wei‐Fang Su and co‐workers incorporate a cation of acetamidinium (Aa⁺) into conventional perovskite layer (MAPbI₃). The Aa⁺ cation effectively hinders the ion migration and enhances the long‐term stability of perovskite solar cells. The champion device achieves 20.68% efficiency. More than 80% of initial power conversion efficiency is maintained after 1300 h of 85°C/85 RH% test as encapsulated.

The charge‐extracting properties of PC₆₀BM, the electron transporting layer (ETL) widely used in perovskite solar cells, are greatly enhanced by complementing with Al:ZnO and triphenyl‐phosphine oxide films. Using these triple‐ETL results in a major improvement in device performance in terms of both efficiency and stability, due to better energy alignment, reduced trap‐assisted recombination, and higher built‐in voltage.

Abstract

Power conversion efficiencies of perovskite solar cells (PSCs) have rapidly increased from 3.8% to a certified 25.2% within only a decade. Eliminating possible recombination losses at the interfaces is essential to further improve both efficiency and stability of this class of emerging photovoltaic technology. Herein, a simple approach for improving the electron extraction of the PC₆₀BM electron transport layer (ETL) is presented by sequentially depositing Al:ZnO (AZO) and triphenyl‐phosphine oxide (TPPO) on top of it, in a p–i–n device configuration. The efficiency of the resulting CH₃NH₃PbI₃‐based solar cell is shown to improve from 14.6%, measured for the control PC₆₀BM‐only cell, to 17.9% for double‐ETL (PC₆₀BM/AZO) and 19.2% for triple‐ETL (PC₆₀BM/AZO/TPPO)‐based devices, respectively. Optimized triple‐ETL‐based cells exhibit high fill factor of 82%. The combination of electrical and quantum mechanical calculations shows that efficiency improvement is attributed to reduced trap‐assisted recombination at the interface and better energy level alignment due to chemical interactions between PC₆₀BM, AZO, and TPPO. Moreover, it is shown that the use of multilayer ETL results in better device stability (T ₈₀ ≈ 800 h) under constant illumination. This work opens new possibilities for inexpensive highly efficient and stable multilayered contacts for PSCs by combining organic small molecules and metal oxides.

Perovskite light‐emitting diodes attract much attention because of their advantages such as high color purity, easy and wide color tunability, and high photoluminescence quantum yields. The recent developments of ideal multifunctional charge transport layers are discussed by considering the fundamental limitations including defects, morphological and phase instability, high refractive index, and poor outcoupling of perovskites.

Abstract

Despite their low exciton‐binding energies, metal halide perovskites are extensively studied as light‐emitting materials owing to narrow emission with high color purity, easy/wide color tunability, and high photoluminescence quantum yields. To improve the efficiency of perovskite light‐emitting diodes (PeLEDs), much effort has been devoted to controlling the emitting layer morphologies to induce charge confinement and decrease the nonradiative recombination. The interfaces between the emitting layer and charge transporting layer (CTL) are vulnerable to various defects that deteriorate the efficiency and stability of the PeLEDs. Therefore, the establishment of multifunctional CTLs that can improve not only charge transport but also critical factors that influence device performance, such as defect passivation, morphology/phase control, ion migration suppression, and light outcoupling efficiency, are highly required. Herein, the fundamental limitations of perovskites as emitters (i.e., defects, morphological and phase instability, high refractive index with poor outcoupling) and the recent developments with regard to multifunctional CTLs to compensate such limitations are summarized, and their device applications are also reviewed. Finally, based on the importance of multifunctional CTLs, the outlook and research prospects of multifunctional CTLs for the further improvement of PeLEDs are discussed.

A universal synthetic strategy is proposed for encapsulation and in situ passivation of perovskite nanocrystals in AlPO‐5 zeolite. The perovskite–zeolite composite exhibits enhanced photoluminescence emission and ultrahigh stability under ambient exposure or in water.

Abstract

Metal halide perovskites have been widely applied in optoelectronic fields, but their poor stability hinders their actual applications. A perovskite–zeolite composite was synthesized via in situ growth in air from aluminophosphate AlPO‐5 zeolite crystals and perovskite nanocrystals. The zeolite matrix provides quantum confinement for perovskite nanocrystals, achieving efficient green emission, and it passivates the defects of perovskite by H‐bonding interaction, which leads to a longer lifetime compared to bulk perovskite film. Furthermore, the AlPO‐5 zeolite also acts as a protection shield and enables ultrahigh stability of perovskite nanocrystals under 150 °C heat stress, under a 15‐month long‐term ambient exposure, and even in water for more than 2 weeks, respectively. The strategy of in situ passivation and encapsulation for the perovskite@AlPO‐5 composite was amenable to a range of perovskites, from MA‐ to Cs‐based perovskites. Benefiting from high stability and photoluminescence performance, the composite exhibits great potential to be virtually applied in light‐emitting diodes (LEDs) and backlight displays.

A bilinkable contact passivation strategy is developed for modifying charge kinetics at the charge transport layer:active layer interface in solar cells. The use of the bifunctional molecule 3‐thiophenecarboxylic acid (TCA) passivates undercoordinated Ti (ETL‐side) and Pb (perovskite‐side), enabling efficient electron extraction through the interface. TCA‐treated films show an increase of PCE of 21.2% compared to 19.8% for reference devices.

Abstract

Charge recombination due to interfacial defects is an important source of loss in perovskite solar cells. Here, a two‐sided passivation strategy is implemented by incorporating a bilinker molecule, thiophene‐based carboxylic acid (TCA), which passivates defects on both the perovskite side and the TiO₂ side of the electron‐extracting heterojunction in perovskite solar cells. Density functional theory and ultrafast charge dynamics reveal a 50% reduction in charge recombination at this interface. Perovskite solar cells made using TCA‐passivated heterojunctions achieve a power conversion efficiency of 21.2% compared to 19.8% for control cells. The TCA‐containing cells retain 96% of initial efficiency following 50 h of UV‐filtered MPP testing.

An N‐type semiconductor material, (CH₃)₂Sn(COOH)₂ (CSCO), is prepared for the first time as an electron transport layer for n‐i‐p planar perovskite solar cells, which leads to one of the highest power conversion efficiencies of 22.21%, and to remarkable stability, retaining over 83% of its initial power conversion efficiency without encapsulation after 130 days of storage in ambient conditions.

Abstract

The electron transport layer (ETL) has an important influence on the power conversion efficiency (PCE) and stability of n‐i‐p planar perovskite solar cells (PSCs). This paper presents an N‐type semiconductor material, (CH₃)₂Sn(COOH)₂ (abbreviated as CSCO) that is synthesized and prepared for the first time as an ETL for n‐i‐p planar PSCs, which leads to a high PCE of 22.21% after KCl treatment, one of the highest PCEs of n‐i‐p planar PSCs to date. Further analysis reveals that the high PCE is attributed to the excellent conductivity of CSCO because of its more delocalized electron cloud distribution due to its unique −O=C−O− group, and to the defect passivation of the Cs_0.05(FA_0.85MA_0.15)_0.95Pb(I_0.85Br_0.15)₃ (denoted as CsFAMA) perovskite through the interaction between the O (Sn) atoms of CSCO and the Pb (halogen) atoms of CsFAMA at CSCO/CsFAMA interface, while the traditional ETL materials such as SnO₂ film lack this function. In addition to the high PCE, the optimal PSCs using CSCO as ETL show remarkable stability, retaining over 83% of its initial PCE without encapsulation after 130 days of storage in ambient conditions (≈25 °C at ≈40% humidity), much better than the traditional SnO₂‐based n‐i‐p PSCs.

SnO₂ has been applied as an efficient electron transport layer for perovskite solar cells over the past few years. In this progress report, recent advances in SnO₂ modification toward high efficiency and stability are summarized from the perspective of the optimization strategies, and the remaining challenges as well as opportunities for future research are also discussed.

Abstract

The electron transport layer plays a key role in affecting the charge dynamics and photovoltaic parameters in perovskite solar cells. Compared to other counterparts, SnO₂ has unique advantages such as low temperature fabrication and high electron extraction ability, and it receives extra attentions from the research community since the first report. Planar‐type perovskite solar cells based on SnO₂ exhibit a simple architecture and state of art device can achieve a power conversion efficiency of over 23%, which can compete with traditional devices using mesoporous TiO₂. The modification engineering of SnO₂ has contributed significantly to the enhanced device performance during the past years. There is still great potential for further improvement in the efficiency and long‐term stability. Herein recent advances toward modifying the optoelectronic properties of SnO₂ from the perspective of the optimization strategies are summarized and the remaining challenges as well as opportunities for future research are discussed. The continuous efforts dedicated to this exciting field may pave the way for developing commercial perovskite solar cells.