JIALINGBO

High‐responsive photodetection of 2D layered materials can be achieved by employing a photogating mechanism. However, the corresponding response time is rather slow. Here, a Schottky barrier‐controlled phototransistor is reported. A fast response is obtained via a field‐assisted detrapping process of electrons in the perovskite layer. This provides the feasibility to achieve high‐performance photodetectors with both high responsivity and fast response time.

Abstract

Phototransistors are recognized as highly sensitive photodetectors owing to their high gain induced by a photogating effect. However, the response speed of a typical phototransistor is rather slow due to the long lifetime of trapped carriers in the channel. Here, a novel Schottky barrier‐controlled phototransistor that shows ultrahigh sensitivity as well as a fast response speed is reported. The device is based on a channel of few‐layer black phosphorous modified with a MAPbI_{3− x} Cl _x perovskite layer, whose channel current is limited by the Schottky barrier at the source electrode. The photoresponse speed of the device can be tuned by changing the drain voltage, which is attributed to a field‐assisted detrapping process of electrons in the perovskite layer close to the Schottky barrier. Under optimal conditions, the device exhibits a high responsivity of 10⁶–10⁸ A W⁻¹, an ultrahigh specific detectivity up to 9 × 10¹³ Jones, and a response time of ≈10 ms.

Forming CH₃NH₃PbI₃/SnO₂ interfaces not only weakens the gap states induced by CH₃NH₃PbI₃ surfaces but also enhances the band offset compared to CH₃NH₃PbI₃/TiO₂ interfaces. Moreover, the interfacial properties are dependent on the interface atomic configurations. CH₃NH₃PbI₃/SnO₂ interface with PbI and SnO terminations is the most stable model, while that with PbI and O terminations exhibits the best interfacial charge transport efficiency.

Abstract

Understanding the interfacial properties of perovskite/SnO₂ interface is important for perovskite solar cell design and optimization. Here, interfacial structure and transport properties of CH₃NH₃PbI₃/SnO₂ interfaces are investigated comprehensively by density functional theory and experiment. Forming CH₃NH₃PbI₃/SnO₂ interfaces weakens the gap states induced by CH₃NH₃PbI₃ surfaces. The interfacial transport properties are strongly dependent on the interface atomic configurations. The CH₃NH₃PbI₃/SnO₂ interface with PbI and O terminations is more beneficial for hole blocking and electron transporting due to the largest valence band offset compared to the CH₃NH₃PbI₃/SnO₂ interface with other terminations. Moreover, it exhibits a larger electrostatic potential difference compared with CH₃NH₃PbI₃/TiO₂ interface, leading to the higher electron transfer efficiency. Hence, higher power conversion efficiency is achieved based on CH₃NH₃PbI₃/SnO₂ compared to CH₃NH₃PbI₃/TiO₂ structure in experiments. In addition, CH₃NH₃PbI₃/SnO₂ interfaces with PbI terminations are more stable than those with CH₃NH₃I terminations, suggesting PbI₂ layer may be preferentially formed on SnO₂ substrate during CH₃NH₃PbI₃ fabrication process. Such results could provide a useful understanding on CH₃NH₃PbI₃/SnO₂ interface and contribute to new strategies for the interface optimization.

Cores and effect: Dithieno[3,2‐b:2′,3′‐d]pyrrole cored p‐type semiconductors are developed as dopant‐free hole‐transport materials for perovskite solar cells with an efficiency surpassing 20 %. The modification via π‐conjugation extension and N‐alkylation fine‐tunes the HOMO energy levels, hole mobility, solubility, and film‐forming characteristics.

Abstract

Organic p‐type semiconductors with tunable structures offer great opportunities for hybrid perovskite solar cells (PVSCs). We report herein two dithieno[3,2‐b:2′,3′‐d]pyrrole (DTP) cored molecular semiconductors prepared through π‐conjugation extension and an N‐alkylation strategy. The as‐prepared conjugated molecules exhibit a highest occupied molecular orbital (HOMO) level of −4.82 eV and a hole mobility up to 2.16×10⁻⁴ cm² V⁻¹ s⁻¹. Together with excellent film‐forming and over 99 % photoluminescence quenching efficiency on perovskite, the DTP based semiconductors work efficiently as hole‐transporting materials (HTMs) for n‐i‐p structured PVSCs. Their dopant‐free MA_0.7FA_0.3PbI_2.85Br_0.15 devices exhibit a power conversion efficiency over 20 %, representing one of the highest values for un‐doped molecular HTMs based PVSCs. This work demonstrates the great potential of using a DTP core in designing efficient semiconductors for dopant‐free PVSCs.

Imaging and mapping characterization techniques are used to understand the fundamental properties that allow lead halide perovskites to have excellent performance metrics. In this work, commonly‐used and specialized tools that are used characterize halide perovskite materials and solar cells, including electron microscopy, atomic force microscopy, synchrotron‐based X‐ray mapping, and ultrafast and photoluminescence mapping are reviewed.

Abstract

Perovskite solar cells (PSCs) have attracted much attention as efficiencies have gone beyond 24%. To achieve these impressive numbers, the PSC scientific community is working to improve the perovskite optoelectronic properties. Imaging and mapping characterization techniques have been widely used to understand the fundamental properties that allow lead halide perovskites to achieve high performance. In this review, these techniques are evaluated, from simple tools, such as electron microscopy, to more complex systems that include atomic force microscopy, synchrotron‐based X‐ray mapping, and ultrafast and photoluminescence mapping. These tools have helped understand lead halide perovskites and their impressive optoelectronic properties, which make them outstanding materials for solar cell applications.

The impact of light on the stability of perovskite solar cells (PSCs) is comprehensively investigated. Elevated device temperature and excess charge carriers are the driving forces for defect formation and PSC device degradation under illumination, not the photovoltage or strain. Cooling the device and operating at maximum power point can improve PSC stability.

Abstract

With power conversion efficiencies now reaching 24.2%, the major factor limiting efficient electricity generation using perovskite solar cells (PSCs) is their long‐term stability. In particular, PSCs have demonstrated rapid degradation under illumination, the driving mechanism of which is yet to be understood. It is shown that elevated device temperature coupled with excess charge carriers due to constant illumination is the dominant force in the rapid degradation of encapsulated perovskite solar cells under illumination. Cooling the device to 20 °C and operating at the maximum power point improves the stability of CH₃NH₃PbI₃ solar cells over 100× compared to operation under open circuit conditions at 60 °C. Light‐induced strain originating from photothermal‐induced expansion is also observed in CH₃NH₃PbI₃, which excludes other light‐induced‐strain mechanisms. However, strain and electric field do not appear to play any role in the initial rapid degradation of CH₃NH₃PbI₃ solar cells under illumination. It is revealed that the formation of additional recombination centers in PSCs facilitated by elevated temperature and excess charge carriers ultimately results in rapid light‐induced degradation. Guidance on the best methods for measuring the stability of PSCs is also given.

Nature Communications, Published online: 08 July 2019; doi:10.1038/s41467-019-10985-5

Preventing the degradation of metal perovskite solar cells (PSCs) by humid air poses a substantial challenge for their future deployment. We introduce here a two-dimensional (2D) A₂PbI₄ perovskite layer using pentafluorophenylethylammonium (FEA) as a fluoroarene cation inserted between the 3D light-harvesting perovskite film and the hole-transporting material (HTM). The perfluorinated benzene moiety confers an ultrahydrophobic character to the spacer layer, protecting the perovskite light-harvesting material from ambient moisture while mitigating ionic diffusion in the device. Unsealed 3D/2D PSCs retain 90% of their efficiency during photovoltaic operation for 1000 hours in humid air under simulated sunlight. Remarkably, the 2D layer also enhances interfacial hole extraction, suppressing nonradiative carrier recombination and enabling a power conversion efficiency (PCE) >22%, the highest reported for 3D/2D architectures. Our new approach provides water- and heat-resistant operationally stable PSCs with a record-level PCE.

Publication date: August 2019

Source: Nano Energy, Volume 62

Author(s): Daniele Benetti, Efat Jokar, Che-Hsun Yu, Amir Fathi, Haiguang Zhao, Alberto Vomiero, Eric Wei-Guang Diau, Federico Rosei

Graphical abstract

Sulfur‐incorporated bismuth‐based perovskite films are obtained by a low‐pressure vapor‐assisted solution process (LP‐VASP) method. A homogeneous and highly compact MBI film with a narrower bandgap of 1.67 eV is successfully achieved. In addition, the obtained film has a low trap‐state density of 1.9 × 10¹⁶ cm⁻³ and the optimal PCE of MA₃Bi₂I_9‐2x S _x PSCs reached 0.152%.

Methylammonium (MA) bismuth iodide ((CH₃NH₃)₃Bi₂I₉) is a promising perovskite material for solar cell application considering the air stability and the nontoxic lead‐free molecular constitution. However, the further improvement of the device performances is prohibited by the wide bandgap (≈2.1 eV) and unsatisfied crystallinity of the (CH₃NH₃)₃Bi₂I₉ films. Herein, a developed low‐pressure vapor‐assisted solution process (LP‐VASP) method is applied to obtain the sulfur‐incorporated bismuth‐based perovskites films. Due to the presence of sulfur, both the crystal quality and the energy band property are improved effectively in the as‐fabricated lead‐free perovskite films. After a systematic study of the influence of the reaction time on the device performances, the optimized reaction time is found to be 30 min, under which, the sulfur‐incorporated MA₃Bi₂I_9‐2x S _x perovskite films exhibit a reduced bandgap of 1.67 eV and a compact morphology. The corresponding optimal PCE reaches 0.152%. This study provides a new way for the incorporation of sulfur in the lead‐free bismuth‐based perovskite solar cells.

Photostability is one of the most vital challenges for perovskite solar cells (PSCs). With the embedding of black phosphorus (BP), well known for its self‐healing and superior property to regulate charge recombination, into MAPbI₃ perovskites, the associated devices exhibit significant enhancement in photostability. The incorporation of BP effectively inhibits Pb⁰ defect formation and retards hot carrier recombination.

Photostability is one of the most vital challenges for organic–inorganic hybrid perovskite solar cells (PSCs). With the incorporation of black phosphorus (BP), well known for self‐healing and its superior property to regulate charge recombination, into CH₃NH₃PbI₃ perovskites (MAPbI₃/BP), the associated PSCs exhibit significant enhancement in photostability in addition to the photovoltaic (PV) performance. The MAPbI₃/BP‐based PSCs retain ≈94% of initial efficiency after 1000 h continuous white light LED illumination in a dry N₂ glovebox whereas their counterparts without the incorporation of BP decrease to ≈30%. Although BP has very small influence on the morphology and structure of the perovskite crystals, Pb⁰ defects are effectively inhibited and hot carrier recombination is found to be retarded as confirmed by femtosecond optical spectroscopy. The utilization of the material to simultaneously inhibit Pb⁰ defect formation and retard charge recombination, such as BP, is a promising strategy to enhance the photostability of organic–inorganic hybrid perovskite‐based PSCs and their siblings.

Chlorine‐substituted graphdiyne (ClGD) is employed into electron transport layers of MAPbI₃‐based perovskite solar cells. It is experimentally and theoretically demonstrated that the interactions of derivated graphdiyne and PCBM stem from four types of noncovalent bonds, which contribute to the improved device performance. Perovskite solar cells based on the ClGD‐PCBM obtain an enhanced power conversion efficiency (PCE) of 20.34%.

Chlorine‐substituted graphdiyne (ClGD) is employed into electron transport layers (ETLs) of MAPbI₃‐based perovskite solar cells for the first time, forming a high‐quality film with superior film morphology and electrical conductivity as compared with pristine [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) film. Strikingly, a champion power conversion efficiency of 20.34% is achieved, showing a 19% enhancement compared with the counterparts (17.08%). Simultaneously, ClGD‐PCBM‐based devices show suppressed J–V hysteresis. It is experimentally and theoretically demonstrated that the interactions of derivated graphdiyne and PCBM stem from four types of noncovalent bonds, which contribute to the improved device performance. The results suggest that derivated graphdiyne‐based interfacial material is promising for the applications in solar cells and other photoelectric devices.

A high voltage aqueous zinc–organic hybrid flow battery is developed by utilizing a three‐electrolyte, two‐membrane configuration with a high operating voltage of 2.0 V. The acidic positive electrolyte is effectively paired with an alkaline negative electrolyte. The electrochemical reversibility and kinetics of the organic redox species is enhanced by an electrocatalyst.

Abstract

Water‐soluble redox‐active organic molecules have attracted extensive attention as electrical energy storage alternatives to redox‐active metals that are low in abundance and high in cost. Here an aqueous zinc–organic hybrid redox flow battery (RFB) is reported with a positive electrolyte comprising a functionalized 1,4‐hydroquinone bearing four (dimethylamino)methyl groups dissolved in sulfuric acid. By utilizing a three‐electrolyte, two‐membrane configuration this acidic positive electrolyte is effectively paired with an alkaline negative electrolyte comprising a Zn/[Zn(OH)₄]²⁻ redox couple and a hybrid RFB is operated at a high operating voltage of 2.0 V. It is shown that the electrochemical reversibility and kinetics of the organic redox species can be enhanced by an electrocatalyst, leading to a cyclic voltammetry peak separation as low as 35 mV and enabling an enhanced rate capability.

Nonfullerene n‐type organic semiconductors possess unique advantages over inorganic semiconductors and/or fullerene derivatives in perovskite solar cells. This research news article summarizes and discusses the recent development of the multifunctional nonfullerene n‐type organic semiconductors used in perovskite solar cells.

Abstract

Compared to inorganic semiconductors and/or fullerene derivatives, nonfullerene n‐type organic semiconductors present some advantages, such as low‐temperature processing, flexibility, and molecule structure diversity, and have been widely used in perovskite solar cells (PSCs). In this research news article, the recent advances in nonfullerene n‐type organic semiconductors which function as electron‐transporting, interface‐modifying, additive, and light‐harvesting materials in PSCs are summarized. The remaining challenges and promising future directions of nonfullerene‐based PSCs are also discussed.

The rapid development of n‐type polymers has boosted the efficiency of all‐polymer solar cells, which has improved from 2% to 10% in only seven years. There is a strong need to summarize the design criteria, synthesis, structure–property relationships and recent advances of n‐type polymers, which is addressed in this review. Moreover, the challenges and prospects for further development of all‐PSCs are briefly discussed.

Abstract

All‐polymer solar cells (all‐PSCs) based on n‐ and p‐type polymers have emerged as promising alternatives to fullerene‐based solar cells due to their unique advantages such as good chemical and electronic adjustability, and better thermal and photochemical stabilities. Rapid advances have been made in the development of n‐type polymers consisting of various electron acceptor units for all‐PSCs. So far, more than 200 n‐type polymer acceptors have been reported. In the last seven years, the power conversion efficiency (PCE) of all‐PSCs rapidly increased and has now surpassed 10%, meaning they are approaching the performance of state‐of‐the‐art solar cells using fullerene derivatives as acceptors. This review discusses the design criteria, synthesis, and structure–property relationships of n‐type polymers that have been used in all‐PSCs. Additionally, it highlights the recent progress toward photovoltaic performance enhancement of binary, ternary, and tandem all‐PSCs. Finally, the challenges and prospects for further development of all‐PSCs are briefly considered.

A low temperature–processed metal oxide with excellent mechanical properties and thickness‐insensitivity is exploited as an electron transporting layer for high‐efficiency robust flexible polymer solar cells (PSCs). A record efficiency of 11.5% is achieved for the flexible PSCs, and over 91% of initial efficiency is well maintained after 1500 bending cycles.

Abstract

Landmark power conversion efficiency (PCE) over 14% has been accomplished for single‐junction polymer solar cells (PSCs). However, the inevitable fracture of inorganic transporting layers and deficient interlayer adhesion are critical challenges to achieving the goal of flexible PSCs. Here, a bendable and thickness‐insensitive Al‐doped ZnO (AZO) modified by polydopamine (PDA) has emerged as a promising electron transporting layer (ETL) in PSCs. It has special ductility and adhesion to the active layer for improving the mechanical durability of the device. Nonfullerenes PSCs based on PBDB‐T‐2F:IT‐4F with AZO:1.5% PDA (80 nm) ETL yield the best PCE of 12.7%. More importantly, a prominent PCE, approaching 11.5%, is reached for the fully flexible device based on Ag‐mesh flexible electrode, and the device retains >91% of its initial PCE after bending for 1500 cycles. Such thickness insensitivity, mechanical durability, and interfacial adhesion properties for the inorganic ETLs are desired for the development of flexible and wearable PSCs with reliable photovoltaic performance and large‐area roll‐to‐roll printing manufacture.

An oxidized poly(3,4‐ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) monolayer is constructed to demonstrate the in‐plane movement of charge carriers in the charge transfer layer, which possibly leads to severe charge recombination at the interfaces. Consequently, a perovskite solar cell fabricated on the oxidized PEDOT:PSS monolayer yields a power conversion efficiency of 18.8% with a high fill factor of 82%.

Charge extraction at the active layer‐electrode interfaces is critical in obtaining highly efficient planar perovskite solar cells (PSCs). It is commonly achieved by enhancing the charge carrier mobility of the charge transfer layer (CTL) that possesses a desirable energy level. Nevertheless, the in‐plane movement of charge carriers in the CTL possibly leads to severe charge recombination in the presence of defects at the interfaces. To verify this overlooked possibility, herein, an oxidized monolayer of poly(3,4‐ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) hole transfer layer (HTL) is constructed by water rinsing followed by H₂O₂ oxidation. The oxidized PEDOT:PSS monolayer ensures a high charge transfer ability from perovskite to electrode, but at the same time limits in‐plane charge transport. An inverted planar PSC fabricated on the oxidized PEDOT:PSS monolayer yields a power conversion efficiency (PCE) of 18.8%, higher than 17.0% of the control device based on a pristine PEDOT:PSS monolayer. The main contribution comes from the fill factor (FF), which is as high as 82%. Characterizations indicate that the conjugation length of PEDOT chains is decreased after H₂O₂ oxidation, which lowers the conductivity of PEDOT:PSS HTL in the in‐plane direction. This study suggests that the charge recombination at the electrode interfaces due to in‐plane charge transport in the CTLs is not to be neglected.

A betaine‐based zwitterionic polymer poly sulfobetaine methacrylate (PSBMA) is employed as interfacial material in p‐i‐n perovskite solar cells. Through improving the interfacial affinity and regulating the energy level at the anode and cathode, respectively, the power conversion efficiency as well as storage stability of the devices greatly improve. In addition, PSBMA also shows advantages in large active area devices.

To improve the performance of perovskite solar cells (Pero‐SCs), a betaine‐based zwitterionic polymer poly(sulfobetaine methacrylate) (denoted by PSBMA) is employed as interlayers at both the anode and cathode in p‐i‐n Pero‐SCs. 1) At the anode side, PSBMA acts as a glue to stitch the two interfacially unfavorable materials: perovskite and poly(bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine), by which the quality of perovskite films as well as the corresponding device performance greatly improve. 2) At the cathode side, PSBMA smoothes the energy levels between PC₆₁BM and Al, and thus facilitates the electron injection efficiency. The power conversion efficiency (PCE) is promoted from 17.31% to 19.16% after PSBMA is introduced as both anode and cathode sides of the p‐i‐n Pero‐SCs. More importantly, PSBMA also shows great potential for large active area (1 cm × 1 cm) Pero‐SCs, and a PCE as high as 15.7% is achieved.

Embracing perovskite grains in a soft fullerene network represents a new and scalable approach, to make perovskite mechanically stable and thus compatible with flexible substrates. The method is demonstrated to prepare flexible perovskite solar cells with the highest ever reported power conversion efficiency. The superior mechanical stability from device performance under working conditions is characterized in situ.

Abstract

Halide perovskite films processed from solution at low‐temperature offer promising opportunities to make flexible solar cells. However, the brittleness of perovskite films is an issue for mechanical stability in flexible devices. Herein, photo‐crosslinked [6,6]‐phenylC₆₁‐butyric oxetane dendron ester (C‐PCBOD) is used to improve the mechanical stability of methylammonium lead iodide (MAPbI₃) perovskite films. Also, it is demonstrated that C‐PCBOD passivates the grain boundaries, which reduces the formation of trap states and enhances the environmental stability of MAPbI₃. Thus, MAPbI₃ perovskite solar cells are prepared on solid and flexible substrates with record efficiencies of 20.4% and 18.1%, respectively, which are among the highest ever reported for MAPbI₃ on both flexible and solid substrates. The result of this work provides a step improvement toward stable and efficient flexible perovskite solar cells.

The small organic molecule (2‐(1,10‐phenanthrolin‐3‐yl)naphth‐6‐yl)diphenylphosphine oxide is explored as cathode interfacial material to reduce the extraction barrier between phenyl‐C61‐butyric acid methyl ester and Ag. With the better contact quality thanks to this molecule, both opaque and semitransparent p‐i‐n perovskite solar cell achieve improved performance and stability.

Abstract

Metal halide perovskite solar cells (PSCs) in the inverted planar p‐i‐n configuration often employ phenyl‐C61‐butyric acid methyl ester (PC₆₁BM) as electron transport layer, onto which Ag is deposited as outer electrode. However, the energy offset between PC₆₁BM and Ag imposes an energy barrier for electron extraction. In this work, to improve the contact quality of this stack, a small organic molecule (2‐(1,10‐phenanthrolin‐3‐yl)naphth‐6‐yl)diphenylphosphine oxide (DPO) as a cathode interfacial material (CIM), inserted between PC₆₁BM and Ag, is introduced. In devices with the indium tin oxide (ITO)/NiO _x /methylammonium lead iodide (MAPbI₃)/PC₆₁BM/CIM/Ag configuration, it is found that this results in fill factor (FF) and short‐circuit current density values (J _SC) that are up to ≈34% and ≈1 mA cm⁻² higher, respectively, compared to DPO‐free devices. Inserting additional thin ZnO nanoparticle layers further improves the contact quality, leading to a power conversion efficiency of 18.2%. Semitransparent PSCs, utilizing DPO as an interlayer buffer layer are also realised. Resultant devices exhibit improved performance compared to DPO‐free devices. This proves that DPO withstands the sputtering of ITO, and may thus find application in perovskite‐based tandem devices. It is concluded that DPO acts as an excellent cathode modifier, opening new device‐engineering opportunities for p‐i‐n PSCs, especially in their semitransparent implementation.

Organic n‐type materials as electron transport layers (ETLs) in inverted perovskite solar cells (p–i–n PSCs) have attracted many scientists' attention, not only because of their several advantages, including easy synthesis, tunable frontier molecular orbitals, decent electron mobility, and reasonable chemical/thermal stability, but also because of their ability to make large‐scale solution‐processing p–i–n PSCs possible.

Abstract

Organic n‐type materials (e.g., fullerene derivatives, naphthalene diimides (NDIs), perylene diimides (PDIs), azaacene‐based molecules, and n‐type conjugated polymers) are demonstrated as promising electron transport layers (ETLs) in inverted perovskite solar cells (p–i–n PSCs), because these materials have several advantages such as easy synthesis and purification, tunable frontier molecular orbitals, decent electron mobility, low cost, good solubility in different organic solvents, and reasonable chemical/thermal stability. Considering these positive factors, approaches toward achieving effective p–i–n PSCs with these organic materials as ETLs are highlighted in this Review. Moreover, organic structures, electron transport properties, working function of electrodes caused by ETLs, and key relevant parameters (PCE and stability) of p–i–n PSCs are presented. Hopefully, this Review will provide fundamental guidance for future development of new organic n‐type materials as ETLs for more efficient p–i–n PSCs.

Publication date: 19 June 2019

Source: Joule, Volume 3, Issue 6

Author(s): Rui Wang, Jingjing Xue, Lei Meng, Jin-Wook Lee, Zipeng Zhao, Pengyu Sun, Le Cai, Tianyi Huang, Zhengxu Wang, Zhao-Kui Wang, Yu Duan, Jonathan Lee Yang, Shaun Tan, Yonghai Yuan, Yu Huang, Yang Yang

Context & Scale

Summary

Graphical Abstract

The combination of perylene diimide and fullerene results in a new hybrid as electron transporting material (ETM) in inverted perovskite solar cells. This hybrid ETM enables a high power conversion efficiency of 18.6 % and good device stability.

Abstract

Electron transport materials (ETM) play an important role in the improvement of efficiency and stability for inverted perovskite solar cells (PSCs). This work reports an efficient ETM, named PDI‐C₆₀, by the combination of perylene diimide (PDI) and fullerene. Compared to the traditional PCBM, this strategy endows PDI‐C₆₀ with slightly shallower energy level and higher electron mobility. As a result, the device based on PDI‐C₆₀ as electron transport layer (ETL) achieves high power conversion efficiency (PCE) of 18.6 %, which is significantly higher than those of the control devices of PCBM (16.6 %) and PDI (13.8 %). The high PCE of the PDI‐C₆₀‐based device can be attributed to the more matching energy level with the perovskite, more efficient charge extraction, transport, and reduced recombination rate. To the best of our knowledge, the PCE of 18.6 % is the highest value in the PSCs using PDI derivatives as ETLs. Moreover, the device with PDI‐C₆₀ as ETL exhibits better device stability due to the stronger hydrophobic properties of PDI‐C₆₀. The strategy using the PDI/fullerene hybrid provides insights for future molecular design of the efficient ETM for the inverted PSCs.

An innovative interfacial modifier, namely, 3‐phenyl‐2‐propen‐1‐amine (t‐PPEA) is developed for perovskite solar cells to overcome the dilemma of the trade‐off between transport and stability of the device, with a unique “quasi‐coplanar” rigid geometrical configuration and distinct electron delocalization characteristic.

Abstract

Interfacial ligand passivation engineering has recently been recognized as a promising avenue, contributing simultaneously to the optoelectronic characteristics and moisture/operation tolerance of perovskite solar cells. To further achieve a win‐win situation of both performance and stability, an innovative conjugated aniline modifier (3‐phenyl‐2‐propen‐1‐amine; PPEA) is explored to moderately tailor organolead halide perovskites films. Here, the conjugated PPEA presents both “quasi‐coplanar” rigid geometrical configuration and distinct electron delocalization characteristics. After a moderate treatment, a stronger dipole capping layer can be formed at the perovskite/transporting interface to achieve favorable banding alignment, thus enlarging the built‐in potential and promoting charge extraction. Meanwhile, a conjugated cation coordinated to the surface of the perovskite grains/units can form preferably ordered overlapping, not only passivating the surface defects but also providing a fast path for charge exchange. Benefiting from this, a ≈21% efficiency of the PPEA‐modified solar cell can be obtained, accompanied by long‐term stability (maintaining 90.2% of initial power conversion efficiency after 1000 h testing, 25 °C, and 40 ± 10 humidity). This innovative conjugated molecule “bridge” can also perform on a larger scale, with a performance of 18.43% at an area of 1.96 cm².