Chen Weijie

Controlling the film-forming kinetics is critical to obtain appropriate heterojunction morphologies for organic solar cells (OSCs). Herein, by employing an asymmetric π-bridge for acceptor–donor–acceptor (A–D–A) type acceptor, the molecular aggregation and film-forming processes are successfully optimized for the active layers, and realize over 19% high photovoltaic efficiencies. This study provides a new approach to managing the film-forming kinetics for efficient OSCs.

Abstract

Blending morphologies are critical to bulk-heterojunction (BHJ) organic solar cells (OSCs) to realize satisfactory photovoltaic performance. Therefore, rationally manipulating film-forming kinetics is of great importance to building suitable phase-separations to balance exciton dissociation and charge transport. Herein, by employing a unilateral π-bridge approach, a new acceptor, WA6 is reported to optimize the film-forming process of active layers and their microstructures. Meanwhile, the possible influencing factors are proposed, including intermolecular electrostatic interactions and donor/acceptor compatibility in the vital solution-to-film transformation stage. Beneficial from the appropriate fibrous phase-separation, the PM6:WA6 based solar cells refined exciton/charge properties, leading to 15.39% high efficiency and much greater than the control device based on the counterpart acceptor without π-bridge. Furthermore, the WA6 can serve as efficient guest component as well, and achieved 19.21% efficiency in the resultant ternary solar cells. This study provides a feasible approach to modulate the molecular aggregation and film-forming procedure, for the construction of high-performance OSCs with eligible blending morphologies.

S-Gua and A-Gua are used as passivation agents to enlarge the grain sizes and to reduce the defects of MA-free perovskite films by which high-efficiency and stable inverted perovskite solar cells are achieved.

Abstract

Power conversion efficiencies (PCEs) of the methylammonium-free (MA-free) perovskite solar cells (PSCs) are constantly lagging behind those of the most extensively researched triple cation mixed PSCs due to their subpar perovskite films. Here, two guanidine-based passivation agents are proposed, that are, sulfaguanidine (S-Gua) and 1-acetylguanidine (A-Gua) that can be applied to optimize the film quality of MA-free perovskite for minimizing the efficiency discrepancy between the two types of PSCs. Through strong coordination with Pb²⁺ and hydrogen bonding with formamidinium (FA⁺), the two passivation additives can reduce bulk defects and suppress non-radiative recombination, which in turn enhance the charge extraction and transfer efficiency. Consequently, the S-Gua- and A-Gua-treated devices achieve PCEs of 24.34% and 23.77%, respectively. Both PCEs are greater than that of the control device (23.03%), and the 24.34% PCE is comparable with that of the best MA-free inverted PSCs with narrower bandgaps. Moreover, the S-Gua-treated devices maintain 89.3% and 82.0% of their initial PCEs after aging for 800 h and heating (85 °C) for 340 h in ambient air without any encapsulation, respectively. This work offers comprehensive insights into the use of guanidine-based additives to achieve high-quality perovskite films and subsequently state-of-the-art MA-free PSCs.

Inverted CsPbI₃ PSCs treated with inorganic-derived 0D Cs₄PbBr₆ perovskite nanocrystals show improved surface lattice arrangement, achieving a PCE of 21.03% and maintaining 92.48% stability after 1000 h under 1-sun and damp heat conditions. Additionally, a module with a 64 cm² aperture area demonstrates a PCE of 17.39%.

Abstract

The inverted inorganic CsPbI₃ perovskite solar cells (PSCs) are prospective candidates for next-generation photovoltaics owing to inherent robust thermal/photo-stability and compatibility for tandems. However, the performance and stability of the inverted CsPbI₃ PSCs fall behind the n-i-p counterparts due to poor energetic alignment and abundant interfacial defect states. Here, an inorganic 0D Cs₄PbBr₆ with a good lattice strain arrangement is implemented as the surface anchoring capping layer on CsPbI₃. The Cs₄PbBr₆ perovskite induces enhanced electron-selective junction and thus facilitates efficient charge extraction and effectively inhibits non-radiative recombination. Consequently, the CsPbI₃ PSCs with Cs₄PbBr₆ demonstrate the highest power conversion efficiency (PCE) of CsPbI₃-based inverted PSCs, reaching 21.03% PCE from a unit cell and 17.39% PCE from a module with a 64 cm² aperture area. Furthermore, the resulting devices retain 92.48% after 1000 h under simultaneous 1-sun and damp heat (85 °C / 85% relative humidity) environment.

This work demonstrates that the capability of hole molecules to strengthen the interface bonding and interactions between molecules and interfaces is crucial to maximally passivate defects, affording robust interface, inhibition of ion migration, and photostable perovskite solar cells. Consequently, the newly developed mDPA-SFX enables cells with a PCE of 24.8 %, and an excellent T ₈₀ lifetime of 2,238 h at maximum power point tracking.

Abstract

Poor operational stability is a crucial factor limiting the further application of perovskite solar cells (PSCs). Organic semiconductor layers can be a powerful means for reinforcing interfaces and inhibiting ion migration. Herein, two hole-transporting molecules, pDPA-SFX and mDPA-SFX, are synthesized with tuned substituent connection sites. The meta-substituted mDPA-SFX results in a larger dipole moment, more ordered packing, and better charge mobility than pDPA-SFX, accompanying with strong interface bonding on perovskite surfaces and suppressed ion motion as well. Importantly, mDPA-SFX-based PSCs exhibit an efficiency that has significantly increased from 22.5 % to 24.8 % and a module-based efficiency of 19.26 % with an active area of 12.95 cm². The corresponding cell retain 94.8 % of its initial efficiency at maximum power point tracking (MPPT) after 1,000 h (T ₉₅=1,000 h). The MPPT T ₈₀ lifetime is as long as 2,238 h. This work illustrates that a small degree of structural variation in organic compounds leaves considerable room for developing new HTMs for light stable PSCs.

Nature Communications, Published online: 17 August 2024; doi:10.1038/s41467-024-51551-y

The strategic incorporation of a para-amino-2,3,5,6-tetrafluorobenzoic acid (PATFBA) buffer layer at the NiO_X/perovskite heterojunction effectively modulates the interfacial energy levels, enhances hole transport efficiency, and prevents redox reactions by passivating the inevitable surface defects. This synergistic bi-directional interaction optimally improves the quality of NiO_X and buried perovskite interfaces, reduces interfacial recombination, and significantly boosts both photovoltaic performance and stability.

Abstract

The quality of the buried heterojunction of nickel oxide (NiO_X)/perovskite is crucial for efficient charge carrier extraction and minimizing interfacial non-radiative recombination in inverted perovskite solar cells (PSCs). However, NiO_X has limitations as a hole transport layer (HTL) due to energy level mismatch, low conduction, and undesirable redox reactions with the perovskite layer, which impede power conversion efficiency (PCE) and long-term stability. In this study, para-amino 2,3,5,6-tetrafluorobenzoic acid (PATFBA) is proposed as a bifacial defect passivator to tailor the NiO_X/perovskite interface. The acid group and adjacent fluorine atoms of PATFBA effectively passivate NiO_X surface defects, thereby improving its Ni³⁺/Ni²⁺ ratio, hole extraction capability, and energy band alignment with perovskite, while also providing active sites for homogenous nucleation. Meanwhile, the amine and adjacent fluorine atomsstabilize the buried perovskite interface by passivating interfacial defects, resulting in higher crystalline perovskite films with supressed non-radaitive recombination. Furthermore, the PATFBA buffer layer prevents redox reactions between Ni³⁺ and perovskite.These synergistic bi-directional interactions lead to optimized inverted PSCs with a PCE of 20.51% compared to 16.89% for pristine devices and the unencapsulated PATFBA-modified devices exhibit outstanding thermal and long-term stability. This work provides a new engineering approach to buried interfaces through the synergy of functional groups.

A feasible ternary-precursor method with an iodide source self-filling ability is reported for the synthesis of the perovskite quantum dots with high optoelectronic properties. The obtained perovskite quantum dots can suppress the surface defects-induced nonradiative recombination and achieve the high orientation of perovskite quantum dot solids, significantly facilitating charge carrier transport in high-performance solar cells.

Abstract

Perovskite quantum dots (PQDs) become a kind of competitive material for fabricating high-performance solar cells due to their solution processability and outstanding optoelectronic properties. However, the current synthesis method of PQDs is mostly based on the binary-precursor method, which results in a large deviation of the I/Pb input ratio in the reaction system from the stoichiometric ratio of PQDs. Herein, a ternary-precursor method with an iodide source self-filling ability is reported for the synthesis of the CsPbI₃ PQDs with high optoelectronic properties. Systematically experimental characterizations and theoretical calculations are conducted to fundamentally understand the effects of the I/Pb input molar ratio on the crystallographic and optoelectronic properties of PQDs. The results reveal that increasing the I/Pb input molar ratio can obtain ideal cubic structure PQDs with iodine-rich surfaces, which can significantly reduce the surface defects of PQDs and realize high orientation of PQD solids, facilitating charge carrier transport in the PQD solids with diminished nonradiative recombination. Consequently, the PQD solar cells exhibit an impressive efficiency of 15.16%, which is largely improved compared with that of 12.83% for the control solar cell. This work provides a feasible strategy for synthesizing high-quality PQDs for high-performance optoelectronic devices.

Large-scale X-ray detectors based on 2D/3D mixed perovskite are fabricated via spraying coating method. The addition of 2D perovskite effectively inhibits the ion migration of the detector, thus reducing the lowest detection limit. Consequently, the required dose rate for X-ray imaging can be significantly diminished, offering advancements in medical imaging with lower radiation exposure.

Abstract

X-ray detection and imaging are widely used in medical diagnosis, product inspection, security monitoring, etc. Large-scale polycrystalline perovskite thick films possess high potential for direct X-ray imaging. However, the notorious problems of baseline drift and high detection limit caused by ions migration are still remained. Here, ion migration is reduced by incorporating 2D perovskite into 3D perovskite, thereby increasing the ion activation energy. This approach hinders ion migration within the perovskite film, consequently suppressing baseline drift and reducing the lowest detection limit(LOD) of the device. As a result, the baseline drifting declines by 20 times and the LOD reduces to 21.1 nGy s⁻¹, while the device maintains a satisfactory sensitivity of 5.6 × 10³ µC Gy⁻¹ cm⁻². This work provides a new strategy to achieve low ion migration in large-scale X-ray detectors and may provide new thoughts for the application of mixed-dimension perovskite.

Functionalized 2D/3D heterojunction is constructed through reversible iodine-alkenes reaction in 3-butenylamine (BEA) based 2D perovskite (BEA)₂[PbBr₄]. (BEA)₂[PbBr₄] can adsorb photo-generated iodine species during perovskite degradation, inhibiting the iodine loss issue in PSCs. These adsorbed iodine can still react with Pb⁰, eliminating related defects. The resulting PSCs exhibit good operational stability without encapsulation, retaining ≈94% of initial efficiency after MPP tracking for 2000 h at 65 °C with ISOS-L-2 protocol.

Abstract

Long-term operational stability remains a big challenge for perovskite solar cells (PSCs), especially under ISOS protocol with high temperature. One key reason lies in the iodine loss issue during PSCs aging. Motived by the reversible iodine-alkenes reaction, 3-butenylamine (BEA) based 2D perovskite (BEA)₂[PbBr₄] is used to construct a functionalized 2D/3D heterojunction in PSCs. (BEA)₂[PbBr₄] can chemically adsorb photo-generated iodine species during perovskite degradation through a typical reaction between neutral iodine and terminal alkenes, thus inhibiting iodine loss or diffusion in PSCs. Besides, owing to the reversible reaction nature, these adsorbed iodine species can be partially released slowly under heat conditions, further reacting with and eliminating potential metallic Pb⁰ defects. The resulting PSCs exhibit a high efficiency of 24.5% with good operational stability even without encapsulation, retaining ≈94% of initial efficiency after MPP tracking for 2000 h at 65 °C with ISOS-L-2 protocol.

A dual-interface modification strategy is employed not only to passivate the perovskites but also to induce homogenous crystallization and reduce residual stress in the perovskite film. Specially, APC interlayer eliminates the localized edge states induced by the iodine vacancies near the conduction band edge and enables homogenous crystallization due to the uniform molecular adsorption energy. As a result of this dual interface modification strategy, a champion PCE of 24.57% is achieved for the inverted PSCs built on a NiOx/PTAA bilayer HTL.

Abstract

Interfacial defects between perovskite and adjacent charge transport layers present a significant obstacle, hindering the enhancement of power conversion efficiency (PCE) and stability in perovskite solar cells (PSCs). To address this challenge, a dual-interface modification is proposed to aim at improving the performance of mixed-halide PSCs. Specifically, the hole-collecting side is modified with 5-Aminopyridine-2-carboxylic Acid (APC), while the electron-collecting side is modified with 2-thiopheneethylammonium chloride (TEACl). The multifunctional APC enhances charge transfer by tailoring the interface between the perovskite and poly(triarylamine) (PTAA) through multiple bonding interactions, thereby suppressing interfacial nonradiative recombination. Density functional theory studies reveal that APC on the perovskite surface induces uniform adsorption energy, promoting homogenous crystallization without residual stress. Additionally, APC interlayer eliminates the localized edge states induced by the iodine vacancies near the conduction band edge. Further improvement in the device performance is achieved by passivating the top perovskite surface with TEACl, leading to well-matched energy bands and reduced vacancy trap states. As a result, champion cell achieves a PCE of 24.87% with an open-circuit voltage of 1.188 V. Furthermore, The dual-interface modification improves thermal stability due to enhanced ion-migration activation energy.

A functionalized ultraviolet-conversion small molecule is judiciously introduced into perovskite to effectively enhance device efficiency and operational stability. Benefiting from the down-conversion effect and stabilized perovskite structure with remarkably reduced intrinsic defects, the resultant device produces substantially increased photocurrent, resulting in a champion PCE of 24.73%, accompanied by greatly improved resistance to ultraviolet radiation, thermal stress, and illumination.

Abstract

Despite the swift development in perovskite solar cells (PSCs), great concerns regarding environmental vulnerability propose a big challenge for their long-term operational stability. Herein, a novel functionalized ultraviolet (UV) conversion small molecule, Coumarin 153 (C153), is judiciously introduced into perovskite precursor to effectively enhance device efficiency and operational stability against UV radiation. It is found that the uncoordinated Pb²⁺ and A-site vacancies of perovskite can be successfully fixed through Lewis acid–base coordination and hydrogen bonding upon C153 treatment, resulting in a stabilized structure with remarkably reduced intrinsic defects. Concurrently, the incremental visible light absorption derived from the down-conversion effect of C153 molecules together with the optimized energy level arrangement contribute to the substantially enhanced photocurrent of the device. As a result, the resultant device delivers a champion efficiency of 24.73%, accompanied by greatly improved operational stability against environments, with retaining over 90% of initial PCE for ≈380, ≈1400, and 1710 h aging under continuous UV radiation, heating stress, and illumination, respectively. This work provides an effective and feasible strategy toward high-efficiency and environment-stable PSCs.

Publication date: November 2024

Source: Nano Energy, Volume 130

Author(s): Jiaheng Nie, Yaming Zhang, Jizheng Wang, Lijie Li, Yan Zhang

Publication date: 20 November 2024

Source: Joule, Volume 8, Issue 11

Author(s): Xingcheng Li, Shuang Gao, Xin Wu, Qi Liu, Leilei Zhu, Chenyue Wang, Yangkai Wang, Zheng Liu, Wenjing Chen, Xinyu Li, Peng Xiao, Qiuping Huang, Tao Chen, Zhenyu Li, Xingyu Gao, Zhengguo Xiao, Yalin Lu, Xiaocheng Zeng, Shuang Xiao, Zonglong Zhu

Publication date: 20 November 2024

Source: Joule, Volume 8, Issue 11

Author(s): Min Ju Jeong, Jae Won Ahn, Soo Woong Jeon, Sung Yong Kim, Jun Hong Noh

State-of-the-art perovskite solar cells (PSCs) continue to encounter stability challenges because of the instable organic component within the light-absorbing layer. Herein, the study has developed a surface Formamidine (FA) cation immobilization strategy through hydrogen bond effect, accompanied by surface Cl^– doping, to obtain stable FA-based perovskites. The resultant perovskite demonstrates outstanding light/thermal stability and significant improved photovoltaics performance.

Abstract

State-of-the-art perovskite solar cells (PSCs) continue to encounter stability challenges throughout their current commercialization process, primarily due to the instable organic components. Especially, surface (interface) imperfections, like the undercoordinated Pb²⁺ and halide sites, further compromise the confinement of organic cations at the surface (interface) and provide a rapid pathway for ion migration and volatilization, decreasing stability and efficiency. Herein, the study has developed a surface Formamidine (FA) cation immobilization strategy through hydrogen bond effect, achieved by a post-treatment of piperazine dihydrochloride (PDCl₂), to obtain stable FA-based perovskites. The piperazine can immobilize surface FA⁺ cation through hydrogen bond. Moreover, the post-treatment of PDCl₂ can induce surface Cl^– doping to establish strong coordinating bond with the uncoordinated Pb²⁺, reducing the imperfections of surface octahedral cage. Such a synergistic effect effectively constrains surface FA⁺ cations, simultaneously alleviates surface lattice stress. Because of improved surface properties, the resultant perovskite demonstrates not only outstanding light/thermal stability, but also more pronounced n-type characteristics and uniform potential distribution for improving charge transfer dynamics. Finally, the champion PSCs exhibit a significantly enhanced efficiency from 23.15% to 25.52%. Moreover, these PSCs exhibit excellent stability: retain 91% of their initial efficiency after over 1000 h maximum power point test.

Substrate-induced re-growth strategy is proposed to induce p- to n-transition of perovskite surface. Bulk perovskite grows on ITO/P3CT-N and shows p-type, while its surface re-grows on ITO/SnO₂ and transits to n-type, introducing an interfacial junction. Resulting inverted perovskite solar cells exhibit >25% efficiency with good stability, retaining 90% of initial efficiency after MPP tracking for 800 h at 65 °C.

Abstract

The p- or n-type property of semiconductor materials directly determine the final performance of photoelectronic devices. Generally, perovskite deposited on p-type substrate tends to be p-type, while perovskite deposited on n-type substrate tends to be n-type. Motived by this, a substrate-induced re-growth strategy is reported to induce p- to n-transition of perovskite surface in inverted perovskite solar cells (PSCs). p-type perovskite film is obtained and crystallized on p-type substrate first. Then an n-type ITO/SnO₂ substrate with saturated perovskite solution is pressed onto the perovskite film and annealed to induce the secondary re-growth of perovskite surface region. As a result, p- to n-type transition happens and induces an extra junction at perovskite surface region, thus enhancing the built-in potential and promoting carrier extraction in PSCs. Resulting inverted PSCs exhibit high efficiency of over 25% with good operational stability, retaining 90% of initial efficiency after maximum power point (MPP) tracking for 800 h at 65 °C with ISOS-L-2 protocol.

The self-assembled 2D perovskite layer (BA₂PbBr₄) is engineered as a tunneling layer to mitigate the band alignment mismatch between SnO₂ and wide bandgap perovskite layers. This approach significantly enhanced the open-circuit voltage, achieving values of 1.30 and 1.33 V, and resulted in power conversion efficiencies of 21.54% and 19.16% for bandgaps of 1.7 and 1.8 eV, respectively.

Abstract

Reducing non-radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high-performance wide-bandgap perovskite solar cells. This study proposes the self-organization of a thin two-dimensional (2D) perovskite BA₂PbBr₄ layer beneath a wide-bandgap three-dimensional (3D) perovskite Cs_0.17FA_0.83Pb(I_0.6Br_0.4)₃, forming a 2D/3D bilayer structure on a tin oxide (SnO₂) layer. This process is driven by interactions between the oxygen vacancies on the SnO₂ surface and hydrogen atoms of the n-butylammonium cation, aiding the self-assembly of the BA₂PbBr₄ 2D layer. The 2D perovskite acts as a tunneling layer between SnO₂ and the 3D perovskite, neutralizing the energy level mismatch and reducing non-radiative recombination. This results in high power conversion efficiencies of 21.54% and 19.16% for wide-bandgap perovskite solar cells with bandgaps of 1.7 and 1.8 eV, with open-circuit voltages over 1.3 V under 1-Sun illumination. Furthermore, an impressive efficiency of over 43% is achieved under indoor conditions, specifically under 200 lux white light-emitting diode light, yielding an output voltage exceeding 1 V. The device also demonstrates enhanced stability, lasting up to 1,200 hours.

Here, thiourea isomer derivatives [(3,5-dichlorophenyl)amino]thiourea (AT) and N-(3,5-dichlorophenyl)hydrazinecarbothioamide (HB) were developed. It is found that AT can effectively regulate crystallization process and passivate defects of perovskite by binding with undercoordinated Pb²⁺ through synergistic interaction between N1 and C=S group with a defect formation energy of 1.80 eV. The AT-treated device engenders an efficiency of 25.71 % and excellent stability.

Abstract

Various isomers have been developed to regulate the morphology and reduce defects in state-of-the-art perovskite solar cells (PSCs). To insight the structure-function-effect correlations for the isomerization of thiourea derivatives on the performance of the PSCs, we developed two thiourea derivatives [(3,5-dichlorophenyl)amino]thiourea (AT) and N-(3,5-dichlorophenyl)hydrazinecarbothioamide (HB). Supported by experimental and calculated results, it was found that AT can bind with undercoordinated Pb²⁺ defect through synergistic interaction between N1 and C=S group with a defect formation energy of 1.818 eV, which is much higher than that from the synergistic interaction between two −NH− groups in HB and perovskite (1.015 eV). Moreover, the stronger interaction between AT and Pb²⁺ regulates the crystallization process of perovskite film to obtain a high-quality perovskite film with high crystallinity, large grain size, and low defect density. Consequently, the AT-treated FACsPbI₃ device engenders an efficiency of 25.71 % (certified as 24.66 %), which is greatly higher than control (23.74 %) and HB-treated FACsPbI₃ devices (25.05 %). The resultant device exhibits a remarkable stability for maintaining 91.0 % and 95.2 % of its initial efficiency after aging 2000 h in air condition or tracking at maximum power point for 1000 h, respectively.

Nature Energy, Published online: 13 August 2024; doi:10.1038/s41560-024-01608-5

Nature Energy, Published online: 15 August 2024; doi:10.1038/s41560-024-01613-8

Publication date: 16 October 2024

Source: Joule, Volume 8, Issue 10

Author(s): Jianhua Han, Han Xu, Anirudh Sharma, Maxime Babics, Jules Bertrandie, Xunchang Wang, Luis Huerta Hernandez, Yongcao Zhang, Yuanfan Wen, Diego Rosas Villalva, Nicolas Ramos, Sri Harish K. Paleti, Jaime Martin, Fuzong Xu, Joel Troughton, Renqiang Yang, Julien Gorenflot, Frédéric Laquai, Stefaan De Wolf, Derya Baran

This work presents a ternary passivation strategy designed to enhance carrier collection and transportation, manage the energy level match, thereby suppressing the recombination process to improve device performance. In the end, the champion device demonstrates outstanding performance, achieving an efficiency of 14.64%. Importantly, the device also exhibits robust operational and stored stability.

Abstract

The exploration of nontoxic Sn-based perovskites as a viable alternative to their toxic Pb-based counterparts has garnered increased attention. However, the power conversion efficiency of Sn-based perovskite solar cells lags significantly behind their Pb-based counterparts. This study presents a ternary passivation strategy aimed at enhancing device performance, employing [6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM), poly(3-hexylthiophene) (P3HT), and indene C60 bisadduct (ICBA). These components play crucial roles in managing energy levels and enhancing carrier transportation, respectively. The results reveal that the introduction of the ternary system leads to improvements in carrier collection and transportation, accompanied by a suppression of the recombination process. Ultimately, the champion device achieves a remarkable performance with an efficiency of 14.64%. Notably, the device also exhibits robust operational and long-term stored stability.

Chiral graphene quantum dots significantly improve perovskite solar cell (PSC) performanceby passivating defects at interface and improve film quality, leading to increased charge extraction and reduced nonradiative recombination. This boosts PSC efficiency from 20.77% to 22.15% under 1 sun and from 21.01% to 31.64% indoors, highlighting the potential of chiral interface engineering.

In the rapidly advancing field of perovskite solar cells (PSCs), achieving the Shockley–Queisser efficiency limit is primarily hindered by nonradiative recombination losses. In this study, the strategic incorporation of chiral graphene quantum dots (GQDs) at the PSC interface is pioneered, significantly mitigating these losses through this chiral interface engineering. Also in this study, by synthesizing and characterizing the chiroptic behavior and doping effects of both chiral and racemic GQDs, their pivotal role in enhancing charge extraction and transport is unveiled. In the findings of this study, it is shown that GQDs do not alter the crystallization of perovskite films but significantly boost light absorption owing to improved interfacial contact. Subsequent optical and electrical assessments reveal that the PSCs treated with chiral GQDs outperform those with racemic GQDs, primarily on account of the chiral specificity of chiral GQDs, which leads to reduced nonradiative recombination and enhanced charge transport efficiency. In this work, not only the potential of chiral GQDs is underscored in elevating PSC efficiency but also a compelling proof of concept for chiral interface engineering is established as a key to unlocking the full potential of PSCs.

By introducing self-additive spacer cation of glycine ethyl ester (Gly-E), the efficient and stable 2D PSCs with high film-quality are obtained. Gly-E exhibits suitable 2D formation energy to easily form 2D perovskite and better self-additive effect. Hence, the Gly-E 2D PSC (n = 6) display a champion PCE of 21.60%, which is one of the highest PCE among 2D PSCs with n ≤ 6.

Abstract

2D Ruddlesden–Popper perovskites are highly regarded materials for improving the stability of perovskite solar cells (PSCs). Wherein, self-additive 2D perovskites have recently been proposed to provide substantial strategies for managing the crystallization kinetics and bulk defects. For a profound understanding of the formation mechanisms, herein, with selecting three self-additive 2D perovskites as demonstrations, a comprehensive analysis of the self-additive behavior combing experimental and theoretical calculations is conducted. Self-additive 2D perovskites exhibit more suitable formation energies and strong interaction, which is conducive to realize the self-additive effect to form more stable structure. As demonstrated, glycine (Gly)-based spacer cations played a pivotal role in the nucleation and growth of 2D perovskites by adjusting the aggregation state of colloids precursor, resulting in excellent-quality films with large average grain size (≈3 µm). Meanwhile, theoretical analysis of electronic distribution and binding energies (E _b) revealed that glycine ethyl ester (Gly-E) perovskite possesses highly robust internal interactions, which will effectively mitigate defect formation and enhance device stability. Endowing with the above outstanding feature, Gly-E devices exhibited an optimized PCE of 21.60%, one of the highest PCEs among all 2D RP PSCs (n ≤ 6). The findings provide a basis for the rational design of self-additive 2D perovskites and achieving highly-performance 2D RP PSCs.

A series of tetrapodal hole-collecting monolayer materials based on a saddle-like cyclooctatetraene core were developed. These molecules were found to form monolayers on transparent electrode substrates, with some phosphonic acid anchoring groups pointing upward, resulting in hydrophilic surfaces. The perovskite solar cell devices using these hole-collecting monolayers exhibit high power conversion efficiencies of up to 21.7 % and good operational stability.

Abstract

Hole-collecting monolayers have greatly advanced the development of positive-intrinsic-negative perovskite solar cells (p-i-n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI-C3 and 4PATTI-C4, by employing a saddle-like indole-fused cyclooctatetraene as a π-core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI-C4 as the hole-collecting monolayer, 4PATTI-C3-based devices exhibit a faster hole-collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini-cell (0.1 cm²) and a mini-module (1.62 cm²), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole-collecting monolayers after being adsorbed onto TCO substrates.