Chen Weijie

Recent progress in the fabrication of CsPbIBr₂ perovskite films and their applications in halide perovskite solar cells are overviewed, with special attention paid to the fabrication technique modification of CsPbIBr₂ films and the resulting performance enhancement of the photovoltaic devices.

CsPbIBr₂ photovoltaic materials attract remarkable attention in the field of all‐inorganic halide perovskite solar cells (HPSCs) due to their superior humidity stability and heat endurance. Since the first report in 2016, the power conversion efficiency (PCE) of CsPbIBr₂‐based HPSCs (Cs‐HPSCs) has increased from 4.7% to 11.53% with an almost 2.5‐fold leap in a short time. Cs‐HPSCs have also become one of the most researched materials in the all‐inorganic perovskite family. Here, the crystal structure and spectrum properties of CsPbIBr₂ are first elucidated to provide a preliminary overview. Subsequently, significantly modified strategies, including various assisting procedures for spin coating, interface engineering, and element impurity doping for superior perovskites and better‐performing cells are meticulously introduced. Overall, the development process of the CsPbIBr₂ materials is focused on, and the feasible strategies to improve fabrication techniques for superior perovskite films and corresponding device PCEs are emphatically summarized, with the aim to provide some constructive guidelines for the rapid development of Cs‐HPSCs.

No rush: High‐efficiency CH₃NH₃PbI₃ perovskite solar cells (19.8 % power‐conversion efficiency, PCE) and large‐area eight‐cell modules (14.2 % PCE, 8.64 V) were readily fabricated from a purified perovskite precursor material, CH₃NH₃PbI₃⋅DMF (see picture). The low volatility of the pure DMSO solvent (as compared to DMF/DMSO) extended the allowable time for low‐speed spin programs and relaxed the precision needed for the antisolvent addition step.

Abstract

A high‐purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH₃NH₃PbI₃⋅DMF, is introduced as an effective precursor material for fabricating high‐quality solution‐processed perovskite layers. Spin‐coated films of the solvent‐intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing. The low volatility of the pure DMSO solvent extended the allowable time for low‐speed spin programs and considerably relaxed the precision needed for the antisolvent addition step. An optimized, reliable fabrication method was devised to take advantage of this extended process window and resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 % power‐conversion efficiency (PCE). The optimized method was also used to fabricate a 22.0 cm², eight‐cell module with 14.2 % PCE (active area) and 8.64 V output (1.08 V/cell).

An ingenious surface chlorination treatment method is used to passivate the interface defects of perovskite/zinc oxide (ZnO), which effectively reduces the interface charge recombination loss and improves the poor interface chemical characteristics. Thus, the fabricated zinc oxide–chlorine (ZnO–Cl)‐based device achieves an enhanced efficiency and suppressed hysteresis, as well as strengthened stability in perovskite solar cells.

Defect states on the zinc oxide (ZnO) surface cause severe interfacial charge recombination and perovskite decomposition during device operation, which inevitably leads to efficiency loss and poor device stability, making the usage of ZnO in perovskite solar cells (PSCs) problematic. Herein, a simple and effective method of inorganic chlorination treatment is used to passivate the surface defects of the ZnO electron transport layer. It is shown that chlorine (Cl) effectively fills the oxygen vacancy defects of ZnO, suppressing charge recombination and facilitating charge transport at the perovskite/ZnO interface. Therefore, the resulting CH₃NH₃PbI₃‐based device achieves an enhanced power conversion efficiency with suppressed hysteresis. Meanwhile, the chlorination of the ZnO surface protects the perovskite layer from decomposition, thus improving device stability. Herein, an ingenious method is developed to further improve the device performance of ZnO‐based PSCs and useful guidance is provided for the development of other perovskite optoelectronics, especially those with ZnO as the charge transport layer.

Intermolecular hydrogen bonding is a potential strategy for organic solar cells to realize low cost, high efficiency, good device and morphology stability, excellent composition, and film thickness tolerance.

Abstract

For comprehensive development of organic solar cells (OSCs), some factors such as environmental stability, low cost, insensitive film thickness, component contents tolerance, and green preparation processes are equally crucial to achieve high power conversion efficiencies (PCEs). In this work, a small molecule 3‐(diethylamino)‐7‐imino‐7H‐benzo[4,5]imidazo[1,2‐a]chromeno[3,2‐c]pyridine‐6‐carbonitrile (DIBC), which is commercially available at low cost, is utilized to realize high‐performance ternary OSCs. Demonstrated via Fourier transform infrared and 2D‐¹HNMR, DIBC can form hydrogen bond interactions with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) in solid films. Further electrostatic potential (ESP) calculations indicate that the hydrogen bond interaction enhances the ESP of PC₇₁BM and accelerates charge transport between donor and acceptor. As a result, poly(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b0]dithiophene‐2,6‐diylalt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl (PTB7‐Th):DIBC:PC₇₁BM‐based ternary OSC achieves a maximum efficiency of 12.17%, which is the best result of green solvent processed fullerene OSCs at present. It is noteworthy that the ternary OSCs also show great tolerance to film thickness and blend ratios. These unique properties are attributed to the hydrogen‐bond‐linked DIBC and PC₇₁BM, which modulates molecule distribution and improves film morphology with an interpenetrating network structure. Furthermore, the DIBC containing device also exhibits good thermal and light radiation stability. These results illustrate that intermolecular hydrogen bond interaction has great potential for realizing high‐performance OSCs.

A novel strategy is reported where control over the surface‐adsorbed water on a transparent conducting oxide substrate is used to mediate the in situ nanocrystalline regrowth of a SnO₂ electron transport layer (ETL) at near room temperature. The new ETL is key to achieving a high power conversion efficiency of 20.5% and 17.5% in rigid and flexible perovskite solar cells, respectively.

Abstract

Electron transport layer (ETL) is a functional layer of great significance for boosting the power conversion efficiency (PCE) of perovskite solar cells (PSCs). To date, it is still a challenge to simultaneously reduce the surface defects and improve the crystallinity in ETLs during their low‐temperature processing. Here, a novel strategy for the mediation of in situ regrowth of SnO₂ nanocrystal ETLs is reported: introduction of controlled trace amounts of surface absorbed water on the fluorinated tin oxide (FTO) or indium–tin oxide (ITO) surfaces of the substrates using ultraviolet ozone (UVO) pretreatment. The optimum amount of adsorbed water plays a key role in balancing the hydrolysis–condensation reactions during the structural evolution of SnO₂ thin films. This new approach results in a full‐coverage SnO₂ ETL with a desirable morphology and crystallinity for superior optical and electrical properties, as compared to the control SnO₂ ETL without the UVO pretreatment. Finally, the rigid and flexible PSC devices based on the new SnO₂ ETLs yield high PCEs of up to 20.5% and 17.5%, respectively.

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.

Crystalline DRCN5T is used to optimize the performance of thick‐film ternary organic solar cells by forming obvious interpenetrating network morphology with decreased π‐π stacking and enhanced domain purity. More importantly, DRCN5T can precisely modulate vertical distribution of the active layer due to contrasting miscibility with PTB7‐Th and PC₇₀BM, which drives the enrichment of PTB7‐Th on the active layer surface.

Abstract

Blending multidonor or multiacceptor organic materials as ternary devices has been recognized as an efficient and potential method to improve the power conversion efficiency of bulk heterojunction devices or single‐junction components in tandem design. In this work, a highly crystalline molecule, DRCN5T, is involved into a PTB7‐Th:PC₇₀BM system to fabricate large‐area organic solar cells (OSCs) whose blend film thickness is up to 270 nm, achieving an impressive performance of 11.1%. The significant improvement of OSCs after adding DRCN5T is due to the formation of an interconnected fibrous network with decreased π–π stacking and enhanced domain purity, in addition to the optimized vertical distribution of PTB7‐Th and PC₇₀BM, producing more effective charge separation, transport, and collection. The optimized morphology and performance are actually determined by the miscibility in different components, which can be quantitatively described by the Flory–Huggins interaction parameter of −0.80 and 2.94 in DRCN5T:PTB7‐Th and DRCN5T:PC₇₀BM blends, respectively. The findings in this work can potentially guide the selection of an appropriate third additive for high‐performance OSCs for the sake of large‐area printing and roll‐to‐roll fabrication from the view of miscibility.

SnO₂ has recently emerged as an attractive n‐type layer for perovskite solar cells, with advantages of high optical transparency, high electron mobility, UV‐stabilized properties as well as low‐temperature processing. Here, a detailed study of structure and morphology of a critical aspect of these devices is reported—the electron transport layer (ETL)—demonstrating improved energy level alignment, reduced hysteresis, and interfacial recombination, which translates to enhanced device performance and stability.

Abstract

Nanostructured tin (IV) oxide (SnO₂) is emerging as an ideal inorganic electron transport layer in n–i–p perovskite devices, due to superior electronic and low‐temperature processing properties. However, significant differences in current–voltage performance and hysteresis phenomena arise as a result of the chosen fabrication technique. This indicates enormous scope to optimize the electron transport layer (ETL), however, to date the understanding of the origin of these phenomena is lacking. Reported here is a first comparison of two common SnO₂ ETLs with contrasting performance and hysteresis phenomena, with an experimental strategy to combine the beneficial properties in a bilayer ETL architecture. In doing so, this is demonstrated to eliminate room‐temperature hysteresis while simultaneously attaining impressive power conversion efficiency (PCE) greater than 20%. This approach highlights a new way to design custom ETLs using functional thin‐film coatings of nanomaterials with optimized characteristics for stable, efficient, perovskite solar cells.

Highly‐efficient, low‐cost, solution‐processed perovskite solar cells, exhibiting remarkable environmental stability, are reported. The fabrication strategy relies on the rational design of the molecular structure of arylamine‐substituted copper(II) phthalocyanine (CuPc) derivatives, which are used as dopant‐free hole‐transport materials. The resulting devices reach a power conversion efficiency of 19.7% and display enhanced long‐term stability with respect to standard (doped) materials.

Abstract

A power conversion efficiency (PCE) as high as 19.7% is achieved using a novel, low‐cost, dopant‐free hole transport material (HTM) in mixed‐ion solution‐processed perovskite solar cells (PSCs). Following a rational molecular design strategy, arylamine‐substituted copper(II) phthalocyanine (CuPc) derivatives are selected as HTMs, reaching the highest PCE ever reported for PSCs employing dopant‐free HTMs. The intrinsic thermal and chemical properties of dopant‐free CuPcs result in PSCs with a long‐term stability outperforming that of the benchmark doped 2,2′,7,7′‐Tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐Spirobifluorene (Spiro‐OMeTAD)‐based devices. The combination of molecular modeling, synthesis, and full experimental characterization sheds light on the nanostructure and molecular aggregation of arylamine‐substituted CuPc compounds, providing a link between molecular structure and device properties. These results reveal the potential of engineering CuPc derivatives as dopant‐free HTMs to fabricate cost‐effective and highly efficient PSCs with long‐term stability, and pave the way to their commercial‐scale manufacturing. More generally, this case demonstrates how an integrated approach based on rational design and computational modeling can guide and anticipate the synthesis of new classes of materials to achieve specific functions in complex device structures.

In contrast to conjugated donaor–acceptor (D–A) alternating copolymers, incorporating a third component, either D′‐ or A′‐unit, to their D–A type polymer backbones can improve their light absorption, and tune energy levels and interchain packing synergistically. Moreover, the well‐controlled stoichiometry for these components in terpolymers also provides further access to fine‐tune these factors, thus resulting in high photovoltaic performance in polymer solar cells.

Abstract

The development of conjugated alternating donor–acceptor (D–A) copolymers with various electron‐rich and electron‐deficient units in polymer backbones has boosted the power conversion efficiency (PCE) over 17% for polymer solar cells (PSCs) over the past two decades. However, further enhancements in PCEs for PSCs are still imperative to compensate their imperfect stability for fulfilling practical applications. Meanwhile development of these alternating D–A copolymers is highly demanding in creative design and syntheses of novel D and/or A monomers. In this regard, when being possible to adopt an existing monomer unit as a third component from its libraries, either a D′ unit or an A′ moiety, to the parent D–A type polymer backbones to afford conjugated D–A terpolymers, it will give a facile and cost‐effective method to improve their light absorption and tune energy levels and also interchain packing synergistically. Moreover, the rationally controlled stoichiometry for these components in such terpolymers also provides access for further fine‐tuning these factors, thus resulting in high‐performance PSCs. Herein, based on their unique features, the recent progress of conjugated D–A terpolymers for efficient PSCs is reviewed and it is discussed how these factors influence their photovoltaic performance, for providing useful guidelines to design new terpolymers toward high‐efficiency PSCs.

Nature Photonics, Published online: 27 May 2019; doi:10.1038/s41566-019-0435-1

Publication date: 21 August 2019

Source: Joule, Volume 3, Issue 8

Author(s): Xiaopeng Zheng, Joel Troughton, Nicola Gasparini, Yuanbao Lin, Mingyang Wei, Yi Hou, Jiakai Liu, Kepeng Song, Zhaolai Chen, Chen Yang, Bekir Turedi, Abdullah Y. Alsalloum, Jun Pan, Jie Chen, Ayan A. Zhumekenov, Thomas D. Anthopoulos, Yu Han, Derya Baran, Omar F. Mohammed, Edward H. Sargent

Context & Scale

Summary

Graphical Abstract

Nickel oxide (NiO _x ) as the most commonly used hole transport layer in inverted perovskite solar cells is doped by nitrogen for the first time, affording an obvious enhancement of average power conversion efficiency from 15.28% to 17.02%. This is primarily due to increased electrical conductivity and lowered valence band energy of the NiO _x film after nitrogen doping.

Nickel oxide (NiO _x ) is commonly used as a hole transport layer (HTL) in inverted‐structure (p‐i‐n) planar perovskite solar cells (PSCs), playing a critical role in the device performance. However, a solution‐processed NiO _x HTL usually suffers from low electrical conductivity, consequently resulting in an inefficient interfacial charge transport. Herein, a facile method is developed to prepare nitrogen‐doped NiO _x (N:NiO _x ), which is applied as a novel HTL in inverted PSCs for the first time, achieving a decent improvement in average power conversion efficiency (PCE) from 15.28% to 17.02%. The effects of nitrogen doping on the electrical conductivity and the energy band structure of NiO _x as well as the quality of CH₃NH₃PbI₃ perovskite layer atop are studied by a series of characterizations, revealing that nitrogen doping leads to increased electrical conductivity and lowered valence band energy of the NiO _x film, which are beneficial to interfacial hole transport. In addition, the trap density of the CH₃NH₃PbI₃ perovskite film atop N:NiO _x layer is reduced, prohibiting unfavorable charge recombination.

A sulfur/nitrogen‐enriched polyimide (E‐PI) with high glass transition temperature (>200 °C) is synthesized and introduced as an interlayer for inverted‐type polymer:nonfullerene solar cells. The 3 nm‐thick E‐PI interlayers result in the improved efficiency and stability of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b″]dithiophene))‐alt‐(5,5‐(1″,3″‐di‐2‐thienyl‐5″,7″‐bis(2‐ethylhexyl)benzo[1″,2″‐c:4″,5″‐c″]dithiophene‐4,8‐dione))] (PBDB‐T):3,9‐bis(6‐methyl‐2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2″,3″‐d″]‐s‐indaceno[1,2‐b:5,6‐b″]dithiophene) solar cells due to the increased work function (electron mobility) of zinc oxide electron‐collecting buffer layers.

Herein, it is reported that sulfur/nitrogen‐enriched polyimide can act as a stable interlayer for inverted‐type polymer:nonfullerene solar cells because it improves the power conversion efficiency (PCE) and stability of the devices. The sulfur/nitrogen‐enriched polyimide (E‐PI) interlayers are prepared on the zinc oxide layers via the thermal imidization of corresponding films of soluble precursor polymer, poly(N‐(2‐((carboxymethyl)(2‐((5‴‐methyl‐[2,2″:5″,2″:5″,2‴‐quaterthiophen]‐5‐yl)amino)‐2‐oxoethyl)amino)ethyl)‐N‐(2‐(methylamino)‐2‐oxoethyl)glycine acid), which is synthesized from ethylenediaminetetraacetic dianhydride and 5,5‴‐diamino‐2,2″:5″,2″:5″,2‴‐quaterthiophene. The E‐PI films exhibit high glass transition temperature (≈204 °C) and broad optical absorption up to ≈1000 nm (absorption edge). Results show that the average PCE of polymer:nonfullerene solar cells is increased from 10.86% to 11.6% at the E‐PI thickness of 3 nm. In particular, the stability of polymer:nonfullerene solar cells is clearly improved by inserting the 3 nm‐thick E‐PI interlayers.

The fabrication of efficient organic solar cells (OSCs) via the combination of one‐step doctor‐blade printing and solvent vapor annealing (SVA) is reported for the first time. SVA improves the spontaneous stratification of the interlayer between the active layer and electrode. The achieved efficiency of 11.14% is among the highest reported to date for doctor‐blade‐coated OSCs.

A pronounced enhancement of the power conversion efficiency (PCE) by 38% is achieved in one‐step doctor‐blade printing organic solar cells (OSCs) via a simple solvent vapor annealing (SVA) step. The organic blend composed of a donor polymer, a nonfullerene acceptor, and an interfacial layer (IL) molecular component is found to phase‐separate vertically when exposed to a solvent vapor‐saturated atmosphere. Remarkably, the spontaneous formation of a fine, self‐organized IL between the bulk heterojunction (BHJ) layer and the indium tin oxide (ITO) electrode facilitated by SVA yields solar cells with a significantly higher PCE (11.14%) than in control devices (8.05%) without SVA and in devices (10.06%) made with the more complex two‐step doctor‐blade printing method. The stratified nature of the ITO/IL/BHJ/cathode is corroborated by a range of complementary characterization techniques including surface energy, cross‐sectional scanning electron microscopy, grazing incidence wide angle X‐ray scattering, and X‐ray photoelectron spectroscopy. This study demonstrates that a spontaneously formed IL with SVA treatment combines simplicity and precision with high device performance, thus making it attractive for large‐area manufacturing of next‐generation OSCs.

Two perylene diimide (PDI)–based small molecular acceptors containing a 3D Alq₃ core flanked by PDI or PDI2 end units are developed for efficient polymer solar cells. The coordination between Alq₃ and the newly used 4,4′‐bipyridine additive allows a high fill factor, power conversion efficiency, and stability to be simultaneously achieved in PDI‐based polymer solar cells.

Abstract

Two novel perylene diimide (PDI)–based derivatives, Alq₃‐PDI and Alq₃‐PDI2, are synthesized by flanking a 3D tri(8‐hydroxyquinoline)aluminum(III) (Alq₃) core with PDI and a helical PDI dimer (PDI2) to construct high‐performance small molecular nonfullerene acceptors (SMAs). The 3D Alq₃ core significantly suppresses the molecular aggregation of the resulting SMAs, leading to a well‐mixed blend with a PTTEA donor polymer and weak phase separation. Compared with Alq₃‐PDI, the extended π‐conjugation of Alq₃‐PDI2 results in higher‐order molecular packing, which improves the absorption and phase separation behavior. Thus, the Alq₃‐PDI2 devices have higher J _sc and FF values and better device performance, which are further enhanced by a small amount of 4,4′‐bipyridine (Bipy) as an additive. The coordination between Bipy and the Alq₃ core promotes molecular packing and phase separation, which lower charge recombination and enhanced charge collection in the resulting devices. Therefore, a largely improved J _sc of 15.74 mA cm⁻² and very high FF of 71.27% are obtained in the Alq₃‐PDI2 devices, resulting in a power conversion efficiency of 9.54%, which is the best value reported for PDI‐based polymer solar cells. The coordination can also serve as a “molecular lock,” which prevents molecular motion and thus improves device stability.

In situ synthesis of polycrystalline SnO₂ electron‐transfer layers (ETLs) at temperatures as low as 130 °C is developed. The best efficiency of devices fabricated using these ETLs is up to 20.52% for those based on glass and 18% for those based on a flexible substrate, among the best for planar n–i–p‐type perovskite (MAPbI₃) solar cells.

Abstract

A high‐quality polycrystalline SnO₂ electron‐transfer layer is synthesized through an in situ, low‐temperature, and unique butanol–water solvent‐assisted process. By choosing a mixture of butanol and water as a solvent, the crystallinity is enhanced and the crystallization temperature is lowered to 130 °C, making the process fully compatible with flexible plastic substrates. The best solar cells fabricated using these layers achieve an efficiency of 20.52% (average 19.02%) which is among the best in the class of planar n–i–p‐type perovskite (MAPbI₃) solar cells. The strongly reduced crystallization temperature of the materials allows their use on a flexible substrate, with a resulting device efficiency of 18%.

A water‐based TiO₂ nanocrystal solution is developed to use as an electron transport layer for perovskite solar cells that show substantially reduced organic molecules and a high Cl content on the TiO₂ nanocrystal surface, which effectively passivate the interface between TiO₂ and perovskite layer with significantly reduced defects. Corresponding solar cells demonstrate a 20.5% power conversion efficiency and 500 h of operational stability.

Halide perovskite solar cells (PSCs) provide a new opportunity for next‐generation photovoltaic applications. However, traditional low‐temperature solution‐processed TiO₂ that acts as an electron transport layer for PSCs shows an inferior stability compared with solar cells based on high‐temperature (typically 500 °C) TiO₂; however, the high‐temperature process is energy consuming and is not compatible with flexible device processing. Traditional TiO₂ nanoparticles made from titanium tetrachloride dispersed in an organic solvent usually have many organic molecules attached on their surface that lead to the formation of deep‐level defect states during long‐term operations. Herein, environmentally friendly, water‐based Cl‐passivated TiO₂ nanoparticles (W‐TiO₂) are invented, and surface organic molecules are removed by a vacuum rotary evaporation process. W‐TiO₂‐based PSCs can reach up to a 20.5% power conversion efficiency with reduced hysteresis and can maintain 80% of their initial performance after 500 h of continuous operation under 1 sun illumination at the maximum power point. This improved performance is ascribed to the organic‐molecule‐free and Cl‐passivated surfaces. The water‐based TiO₂ nanoparticle dispersion also offers a convenient and universal way to introduce other passivation agents to further improve the photovoltaic performance of PSCs.

Crystalline DRCN5T is used to optimize the performance of thick‐film ternary organic solar cells by forming obvious interpenetrating network morphology with decreased π‐π stacking and enhanced domain purity. More importantly, DRCN5T can precisely modulate vertical distribution of the active layer due to contrasting miscibility with PTB7‐Th and PC₇₀BM, which drives the enrichment of PTB7‐Th on the active layer surface.

Abstract

Blending multidonor or multiacceptor organic materials as ternary devices has been recognized as an efficient and potential method to improve the power conversion efficiency of bulk heterojunction devices or single‐junction components in tandem design. In this work, a highly crystalline molecule, DRCN5T, is involved into a PTB7‐Th:PC₇₀BM system to fabricate large‐area organic solar cells (OSCs) whose blend film thickness is up to 270 nm, achieving an impressive performance of 11.1%. The significant improvement of OSCs after adding DRCN5T is due to the formation of an interconnected fibrous network with decreased π–π stacking and enhanced domain purity, in addition to the optimized vertical distribution of PTB7‐Th and PC₇₀BM, producing more effective charge separation, transport, and collection. The optimized morphology and performance are actually determined by the miscibility in different components, which can be quantitatively described by the Flory–Huggins interaction parameter of −0.80 and 2.94 in DRCN5T:PTB7‐Th and DRCN5T:PC₇₀BM blends, respectively. The findings in this work can potentially guide the selection of an appropriate third additive for high‐performance OSCs for the sake of large‐area printing and roll‐to‐roll fabrication from the view of miscibility.

Inspired by the competitive growth in forests, a competitive growth mechanism‐driven perovskite grain growth approach via CD disk printing wettability‐patterned substrates is proposed to achieve large grain size and avoid the discontinuous perovskite films caused by the nonwettability of substrates, resulting in efficiencies over 20% for the micro‐contact print perovskite solar cells.

Abstract

Novel photovoltaic perovskite solar cells (PSCs) with high‐efficient photovoltaic property are largely in thrall to the uncertain perovskite grain size and inevitable defects. Here, inspired by the competitive growth between tree and grass in the forest system, a competitive perovskite grain growth approach via micro‐contact print (MicroCP) method (CD disk as templates) for printing wettability‐patterned substrate is proposed, aiming to achieve large‐grained perovskite and avoid discontinuous perovskite films caused by the low wettability of substrates. A MicroCP process is employed to construct a patterned wettability surface for the perovskite competitive growth mechanism on the electrode surface. This approach modifies the substrates quickly, ensures the uniform coverage of perovskite due to the function of ‐NH₂ and Pb²⁺ bonds, and converts the perovskite films composed of small grains and pinholes into high‐quality perovskite films, free from pinholes and made up of large grains, resulting in efficiencies over 20% for the MicroCP PSCs.

Inspired by the competitive growth in forests, a competitive growth mechanism‐driven perovskite grain growth approach via CD disk printing wettability‐patterned substrates is proposed to achieve large grain size and avoid the discontinuous perovskite films caused by the nonwettability of substrates, resulting in efficiencies over 20% for the micro‐contact print perovskite solar cells.

Abstract

Novel photovoltaic perovskite solar cells (PSCs) with high‐efficient photovoltaic property are largely in thrall to the uncertain perovskite grain size and inevitable defects. Here, inspired by the competitive growth between tree and grass in the forest system, a competitive perovskite grain growth approach via micro‐contact print (MicroCP) method (CD disk as templates) for printing wettability‐patterned substrate is proposed, aiming to achieve large‐grained perovskite and avoid discontinuous perovskite films caused by the low wettability of substrates. A MicroCP process is employed to construct a patterned wettability surface for the perovskite competitive growth mechanism on the electrode surface. This approach modifies the substrates quickly, ensures the uniform coverage of perovskite due to the function of ‐NH₂ and Pb²⁺ bonds, and converts the perovskite films composed of small grains and pinholes into high‐quality perovskite films, free from pinholes and made up of large grains, resulting in efficiencies over 20% for the MicroCP PSCs.