Chen Weijie

Balancing crystallization, filling the voids at the buried interface and minimizing interfacial recombination losses for record-high MA-free inverted perovskite solar cells is achieved by simultaneously introducing bulk additives ((aminomethyl)phosphonic acid, AMP) and multiple surface passivators (2-(3-fluorophenyl)ethylamine iodide, mF-PEAI and piperazine diiodide, PDI).

Abstract

In a methylammonium-free (MA-free) composition, the uncontrollable crystallization process between Cs and formamidine (FA) currently hinders its efficiency enhancement, especially in inverted perovskite solar cells (PSCs). Here, a dual-interface modification of perovskite films is proposed by simultaneously introducing additives and surface passivators. In particular, (aminomethyl)phosphonic acid (AMP) is introduced into the precursor solution to balance crystallization by inducing the preferential crystallization of FA through the specific formation of strong hydrogen bonds with FA. In addition, AMP spontaneously sinks and anchors to the buried interface to fill the voids of the self-assembled monolayer (SAM) via the covalent bonds formed by ─PO₃H₂ and FTO. Subsequently, by the sequential modification of perovskite surface with 2-(3-fluorophenyl)ethylamine iodide (mF-PEAI) and piperazine diiodide (PDI), a uniform surface potential is achieved and recombination losses at the interface are minimized. Notably, the dual-interface-modified inverted MA-free PSCs achieve a state-of-the-art power conversion efficiency (PCE) of 25.35% (certified: 24.87%) with a satisfactory V _oc of 1.17 V based on the bandgap of 1.52 eV. Importantly, the unencapsulated devices maintain 92.8% and 91.7% of the initial efficiency after 1000 h of maximum power output (MPP) tracking and >800 h of heating at 85 °C, respectively, confirming excellent operational and thermal stability.

Two asymmetric self-assembled molecules, namely BrCz and BrBACz, were designed and synthesized as HTM in organic solar cells (OSCs) based on the system of PM6 : Y6, PM6 : eC9, PM6 : L8-BO, and D18 : eC9. The PM6 : eC9-based binary OSC using BrBACz exhibits a champion efficiency of 19.7 %, which is a record efficiency for binary OSCs. Moreover, the unencapsulated device maintains 95.0 % of its original efficiency after 1000 hours of storage at air ambient.

Abstract

The hole-transporting material (HTM), poly (3,4-ethylene dioxythiophene) poly(styrene sulfonate) (PEDOT : PSS), is the most widely used material in the realization of high-efficiency organic solar cells (OSCs). However, the stability of PEDOT : PSS-based OSCs is quite poor, arising from its strong acidity and hygroscopicity. In addition, PEDOT : PSS has an absorption in the infrared region and high highest occupied molecular orbital (HOMO) energy level, thus limiting the enhancement of short-circuit current density (J _sc) and open-circuit voltage (V _oc), respectively. Herein, two asymmetric self-assembled molecules (SAMs), namely BrCz and BrBACz, were designed and synthesized as HTM in binary OSCs based on the well-known system of PM6 : Y6, PM6 : eC9, PM6 : L8-BO, and D18 : eC9. Compared with BrCz, BrBACz shows larger dipole moment, deeper work function and lower surface energy. Moreover, BrBACz not only enhances photon harvesting in the active layer, but also minimizes voltage losses as well as improves interface charge extraction/ transport. Consequently, the PM6 : eC9-based binary OSC using BrBACz as HTM exhibits a champion efficiency of 19.70 % with a remarkable J _sc of 29.20 mA cm⁻² and a V _oc of 0.856 V, which is a record efficiency for binary OSCs so far. In addition, the unencapsulated device maintains 95.0 % of its original efficiency after 1,000 hours of storage at air ambient, indicating excellent long-term stability.

Publication date: May 2024

Source: Nano Energy, Volume 123

Author(s): Mengqi Jin, Chong Chen, Fumin Li, Zhitao Shen, Hu Shen, Dong Yang, Huilin Li, Ying Liu, Chao Dong, Rong Liu, Mingtai Wang

Efficient energy conversion from sunlight to electricity by dopant-free NiO_x-based inverted perovskite solar cells is achieved with star-shaped truxene-based organic small molecules used as the interfacial layer, which leads to excellent defect passivation of perovskite, minimal nonradiative recombination, and efficient charge extraction. Long-termed stability is also improved for the MAPbI₃-based p-i-n device.

Abstract

Nickel oxide (NiO_x) is commonly used as a holetransporting material (HTM) in p-i-n perovskite solar cells. However, the weak chemical interaction between the NiO_x and CH₃NH₃PbI₃ (MAPbI₃) interface results in poor crystallinity, ineffective hole extraction, and enhanced carrier recombination, which are the leading causes for the limited stability and power conversion efficiency (PCE). Herein, two HTMs, TRUX-D1 (N²,N⁷,N¹² -tris(9,9-dimethyl-9H-fluoren-2-yl)-5,5,10,10,15,15-hexaheptyl-N²,N⁷,N¹² -tris(4-methoxyphenyl)-10,15-dihydro-5H-diindeno[1,2-a:1′,2′-c]fluorene-2,7,12-triamine) and TRUX-D2 (5,5,10,10,15,15-hexaheptyl-N²,N⁷,N¹² -tris(4-methoxyphenyl)-N²,N⁷,N¹² -tris(10-methyl-10H-phenothiazin-3-yl)-10,15-dihydro-5H-diindeno[1,2-a:1′,2′-c]fluorene-2,7,12-triamine), are designed with a rigid planar C ₃ symmetry truxene core integrated with electron-donating amino groups at peripheral positions. The TRUX-D molecules are employed as effective interfacial layer (IFL) materials between the NiO_x and MAPbI₃ interface. The incorporation of truxene-based IFLs improves the quality of perovskite crystallinity, minimizes nonradiative recombination, and accelerates charge extraction which has been confirmed by various characterization techniques. As a result, the TRUX-D1 exhibits a maximum PCE of up to 20.8% with an impressive long-term stability. The unencapsulated device retains 98% of their initial performance following 210 days of aging in a glove box and 75.5% for the device after 80 days under ambient air condition with humidity over 40% at 25 °C.

Phase distribution of two-dimensional perovskite (GA(MA)_nPb_nI_3n+1) is regulated by using potassium salt to control the assembly behavior of colloidal particles and manage the growth of quantum well. The perovskite solar cells achieve an unparalleled PCE of 20.90% with good reproducibility and stability.

Abstract

Two-dimensional (2D) perovskite solar cells (PSCs) exhibit better stability compared with three-dimensional PSCs. However, fundamental questions remain over the chemical phase space in the 2D perovskite framework. Here, phase distribution of alternating cations in the interlayer space 2D perovskite (GA(MA)_nPb_nI_3n+1) is regulated by using potassium salt to control the assembly behavior of colloidal particles and manage the growth of quantum well. The strong affinity between the spacer cation and sulfonate can slow down the intercalation of organic spacer cations to provide a time window for the insertion of MA⁺, which is conducive to forming high n phase to facilitate the charge transportation. During the crystallization process, potassium salt is extruded to the grain boundary and produce a passivation effect. In this case, the ion migration channels and inlet of water and oxygen are cut off, which is beneficial for the stability of PSCs. A power conversion efficiency of 20.90% is obtained in this work, to the best knowledge, which is the highest PCE for all reported GA(MA)₃Pb₃I₁₀ perovskite and the large-area device (1.01 cm²) shows a high efficiency of 18.73 %. Besides, the devices deliver good humidity stability.

A unique intermediate phase engineering strategy is developed to overcome the residual of solvent in unannealed perovskite film by introducing octane-1,8-diamine dihydroiodide. This helps to achieve single junction wide bandgap perovskite solar cells with high efficiency >22% and outstanding stability, and achieve high performance 4-terminal all perovskite and large area perovskite solar cells.

Abstract

Wide bandgap (WBG) perovskite can construct tandem cells with narrow bandgap solar cells by adjusting the band gap to overcome the Shockley−Queisser limitation of single junction perovskite solar cells (PSCs). However, WBG perovskites still suffer from severe nonradiative carrier recombination and large open-circuit voltage loss. Here, this work uses an in situ photoluminescence (PL) measurement to monitor the intermediate phase evolution and crystallization process via blade coating. This work reports a strategy to fabricate efficient and stable WBG perovskite solar cells through doping a long carbon chain molecule octane-1,8-diamine dihydroiodide (ODADI). It is found that ODADI doping not only suppresses intermediate phases but also promote the crystallization of perovskite and passivate defects in blade coated 1.67 eV WBG FA_0.7Cs_0.25MA_0.05Pb(I_0.8Br_0.2)₃ perovskite films. As a result, the champion single junction inverted PSCs deliver the efficiencies of 22.06% and 19.63% for the active area of 0.07 and 1.02 cm², respectively, which are the highest power conversion efficiencies (PCEs) in WBG PSCs by blade coating. The unencapsulated device demonstrates excellent stability in air, which maintains its initial efficiency at the maximum power points under constant AM 1.5G illumination in open air for nearly 500 h. The resulting semitransparent WBG device delivers a high PCE of 20.06%, and the 4-terminal all-perovskite tandem device delivers a PCE of 28.35%.

A top-down engineering strategy of perovskite crystallization is introduced via propylamine chloride (PACl) post treatment of perovskite wet film, inducing downward preferred crystallization orientation and realizing excellent homogeneity in terms of vertical and horizontal scale of perovskite, contributing to a champion PCE of 25.07% for p-i-n PVSCs, as well as the enhanced thermal and operational stability.

Abstract

Crystallization orientation plays a crucial role in determining the performance and stability of perovskite solar cells (PVSCs), whereas effective strategies for realizing oriented perovskite crystallization is still lacking. Herein, a facile and efficient top-down strategy is reported to manipulate the crystallization orientation via treating perovskite wet film with propylamine chloride (PACl) before annealing. The PA⁺ ions tend to be adsorbed on the (001) facet of the perovskite surface, resulting in the reduced cleavage energy to induce (001) orientation-dominated growth of perovskite film and then reduce the temperature of phase transition, meanwhile, the penetrating Cl ions further regulate the crystallization process. As-prepared (001)-dominant perovskite films exhibit the ameliorative film homogeneity in terms of vertical and horizontal scale, leading to alleviated lattice mismatch and lowered defect density. The resultant PVSC devices deliver a champion power conversion efficiency (PCE) of 25.07% with enhanced stability, and the unencapsulated PVSC device maintains 95% of its initial PCE after 1000 h of operation at the maximum power point under simulated AM 1.5G illumination.

Publication date: July 2024

Source: Journal of Energy Chemistry, Volume 94

Author(s): Fumeng Ren, Qian Lu, Xin Meng, Jing Zhou, Rui Chen, Jianan Wang, Haixin Wang, Sanwan Liu, Zonghao Liu, Wei Chen

Publication date: 17 April 2024

Source: Joule, Volume 8, Issue 4

Author(s): Robin Basu, Fabian Gumpert, Jan Lohbreier, Pierre-Olivier Morin, Varun Vohra, Yang Liu, Yinhua Zhou, Christoph J. Brabec, Hans-Joachim Egelhaaf, Andreas Distler

Trifluoromethyl benzylamine is developed as the 2D spacer cation, and the effects of -CF₃ at different substitution positions on the surface morphology, carrier dynamics, and device performances of 2D/3D perovskite solar cells are systematically investigated.

Introducing 2D perovskite onto the surface of 3D perovskite could not only passivate the defects in 3D perovskite, but also protect the 3D perovskite from humidity invasion, which could improve the device stability. The choice of spacer cations in 2D perovskites directly influences the overall properties of the 2D layer, which is crucial to the efficiency and stability of devices. Herein, trifluoromethyl benzylamine is developed as the 2D spacer cation, and the effects of –CF₃ at different substitution positions on the surface morphology, carrier dynamics, and device performances are systematically investigated. Results show that the 3-TFPMAI-treated 2D/3D perovskite film shows smoother morphology, with fewer surface defects and less nonradiative recombination. Moreover, with a matched energy level, 3-TFPMAI modification can accelerate hole extraction and hole transporting. The 3-TFPMAI-treated 2D/3D cell achieves a champion efficiency of 22.68%. What's more, the introduction of fluoride-containing groups increases the hydrophobicity of the 2D layer, which effectively resists moisture erosion and greatly improves the long-term and operational stability of the perovskite solar cells.

Addition of 10 wt% GS-ISO to PM6:BTP-BO-4F improves the surface morphology of the active layer by employing a green solvent (O-xylene) and a hot spin-coating process, resulting in enhanced charge extraction, transport, and collection. The final result is the simultaneous enhancement of V _OC, J _SC, and FF as well as the realization of 18.63% efficiency.

Abstract

The solubility problem of conjugated polymers in nonhalogenated solvents limits the application of nonhalogenated solvents in Organic solar cells (OSCs). By combining with a hot spin-coating process, efficient PM6:BTP-BO-4F:GS-ISO ternary OSCs are prepared by employing o-xylene as a solvent. After adding 10 wt% content of GS-ISO to PM6:BTP-BO-4F, the surface morphology in the active layers is improved and the charge extraction, transport, and collection in OSCs are enhanced. Compared with the efficiency of PM6:BTP-BO-4F OSCs (16.25%), an efficiency of 18.63% is achieved for PM6:BTP-BO-4F:GS-ISO ternary OSCs. Moreover, PM6:BTP-BO-4F:GS-ISO ternary OSCs with an efficiency of 14.13% are prepared in air. The work provides a new strategy for preparing efficient and environmentally friendly OSCs using green solvents.

A new hybrid interface layer, based on an ionic and self-assembled monolayer, strengthens a unidirectional net dipole moment between the hole transport layer and perovskite through ion-dipole interactions between fluorine and 2PACz, which further enhances the charge extraction and reduces the non-radiative recombination rates. In addition, stability is improved owing to the holistic interface passivation of the buried NiO_X/perovskite interface.

Abstract

Nickel oxide (NiO_X) has a crucial role in enhancing the efficiency and stability of p-i-n inverted perovskite solar cells (PSCs), which hold great potential for commercialization. However, improving contact passivation between perovskites and NiO_X is a challenge due to a hindered buried interface. In order to address this issue, self-assembled monolayers (SAMs) are introduced as a buffer layer to prevent direct contact and non-radiative recombination. While, the large dipole moment of SAMs increases the work function of NiO_X, which is crucial for enhancing hole transport performance, given the low interfacial potential barrier for hole transfer. By a combination of the first-principles calculations, drive-level capacitance profiling, and transient absorption spectrum characterization, the understanding of the ion-dipole interactions and interface passivation mechanism of potassium fluoride (KF) ultra-thin buffer layer between SAMs and perovskites is provided. The efficiency of inverted PSCs as high as 23.25% is obtained, and the unencapsulated devices kept 90% of initial efficiency following 1400 h aging under nitrogen, which demonstrate remarkable long-term stability as well. This novel strategy highlights the significance of SAMs dipole moment at the NiO_X/perovskites interface and provides a new approach to address buried interfaces for high-efficiency and long-term stability in inverted PSCs.

Nature Communications, Published online: 05 March 2024; doi:10.1038/s41467-024-46145-7

A feasible dipolar chemical bridge is constructed between the perovskite and TiO₂ layers to lower the photovoltage deficits of perovskite solar cells. The functional molecules could firmly anchor to the TiO₂ surface and chemically bond with the [PbI₆]⁴⁻ octahedral frameworks of perovskites to ameliorate the interfacial disorder and facilitate charge transport, leading to the perovskite solar cells with an efficiency of 21.86 % being realized.

Abstract

CsPbI₃ perovskite receives tremendous attention for photovoltaic applications due to its ideal band gap and good thermal stability. However, CsPbI₃ perovskite solar cells (PSCs) significantly suffer from photovoltage deficits because of serious interfacial energy losses within the PSCs, which to a large extent affects the photovoltaic performance of PSCs. Herein, a dipolar chemical bridge (DCB) is constructed between the perovskite and TiO₂ layers to lower interfacial energy losses and thus improve the charge extraction of PSCs. The results reveal that the DCB could form a beneficial interfacial dipole between the perovskite and TiO₂ layers, which could optimize the interfacial energetics of perovskite/TiO₂ layers and thus improve the energy level alignment within the PSCs. Meanwhile, the constructed DCB could also simultaneously passivate the surface defects of perovskite and TiO₂ layers, greatly lowering interfacial recombination. Consequently, the photovoltage deficit of CsPbI₃ PSCs is largely reduced, leading to a record efficiency of 21.86 % being realized. Meanwhile, the operation stability of PSCs is also largely improved due to the high-quality perovskite films with released interfacial tensile strain being obtained after forming the DCB within the PSCs.

An anti-solvent-free (ASF) technique is devised to fabricate photostable pure-iodide wide-bandgap perovskite solar cells (PSCs). Compared with wide-bandgap PSCs made from anti-solvent process, the ASF method significantly improves the device performance and reproducibility. Furthermore, methylammonium chloride is applied to enhance the crystallinity. Consequently, the ASF-based PSCs deliver a highest PCE of 21.30 % with excellent photostability.

Abstract

The perovskite/silicon tandem solar cell (TSC) has attracted tremendous attention due to its potential to breakthrough the theoretical efficiency set for single-junction solar cells. However, the perovskite solar cell (PSC) designed as its top component cell suffers from severe photo-induced halide segregation owing to its mixed-halide strategy for achieving desirable wide-bandgap (1.68 eV). Developing pure-iodide wide-bandgap perovskites is a promising route to fabricate photostable perovskite/silicon TSCs. Here, we report efficient and photostable pure-iodide wide-bandgap PSCs made from an anti-solvent-free (ASF) technique. The ASF process is achieved by mixing two precursor solutions, both of which are capable of depositing corresponding perovskite films without involving anti-solvent. The mixed solution finally forms Cs_0.3DMA_0.2MA_0.5PbI₃ perovskite film with a bandgap of 1.68 eV. Furthermore, methylammonium chloride additive is applied to enhance the crystallinity and reduce the trap density of perovskite films. As a result, the pure-iodide wide-bandgap PSC delivers efficiency as high as 21.30 % with excellent photostability, the highest for this type of solar cells. The ASF method significantly improves the device reproducibility as compared with devices made from other anti-solvent methods. Our findings provide a novel recipe to prepare efficient and photostable wide-bandgap PSCs.

Py-DB with an extended conjugated structure is an effective dopant-free HTM when applied in n-i-p-type PSCs, affording an efficiency of 24.33 %, the highest PCE for a dopant-free small-molecule HTM.

Abstract

Dopant-free hole transporting materials (HTMs) is significant to the stability of perovskite solar cells (PSCs). Here, we developed a novel star-shape arylamine HTM, termed Py-DB, with a pyrene core and carbon-carbon double bonds as the bridge units. Compared to the reference HTM (termed Py-C), the extension of the planar conjugation backbone endows Py-DB with typical intermolecular π–π stacking interactions and excellent solubility, resulting in improved hole mobility and film morphology. In addition, the lower HOMO energy level of the Py-DB HTM provides efficient hole extraction with reduced energy loss at the perovskite/HTM interface. Consequently, an impressive power conversion efficiency (PCE) of 24.33 % was achieved for dopant-free Py-DB-based PSCs, which is the highest PCE for dopant-free small molecular HTMs in n-i-p configured PSCs. The dopant-free Py-DB-based device also exhibits improved long-term stability, retaining over 90 % of its initial efficiency after 1000 h exposure to 25 % humidity at 60 °C. These findings provide valuable insights and approaches for the further development of dopant-free HTMs for efficient and reliable PSCs.

Publication date: 15 May 2024

Source: Joule, Volume 8, Issue 5

Author(s): Da Seul Lee, Ki Woong Kim, You-Hyun Seo, Myung Hyun Ann, Wonkyu Lee, Jiyeon Nam, Jaehoon Chung, Gabkyung Seo, Seongsik Nam, Boo Soo Ma, Teak-Soo Kim, Yoonmook Kang, Nam Joong Jeon, Jangwon Seo, Seong Sik Shin

Publication date: 17 April 2024

Source: Joule, Volume 8, Issue 4

Author(s): Dongrui Jiang, Zheng Liu, Jinzhao Li, Huanqi Cao, Yicheng Qian, Zhixin Ren, Shifu Zhang, Yuan Qiu, Chao Zhang, Junfeng Wei, Liying Yang, Shougen Yin

Development of large-area all-perovskite tandem solar cells and tandem solar modules (TSMs) is briefly summarized, and the views on the optimization of large-area modules from a forward-looking perspective are put forward. It is believed that more researchers will enter the all-perovskite TSMs field, and it is hoped these insights will help drive the commercial applications of all-perovskite TSMs.

The efficiency of all-perovskite tandem solar cells has recently surpassed that of single-junction perovskite solar cells, showing great potential as a future photovoltaic technology due to its low manufacturing cost and high power conversion efficiency potential, yet the size of these cells is still at the laboratory level. It is highly required to develop scalable preparation methods to fabricate large-area all-perovskite tandem solar modules for commercial applications. Herein, the key challenges encountered in the laboratory of all-perovskite tandem solar cells and the existing solutions are summarized and some views on the preparation of large areas and modules are given.

A mixed solvent of DMF and DMPU is used as the precursor solvent, which not only obviates the need for additional antioxidants but also demonstrates reduced oxidation susceptibility toward Sn–Pb mixed perovskite. A PCE of 21.04% for Sn–Pb mixed perovskite solar cells is achieved by the gas-assisted technique without anti-solvents. The Sn–Pb mixed perovskite solar cells exhibit a <10% reduction in efficiency prepared using the DMF+DMPU solvent after a 28-day age.

Abstract

Tin (Sn)–lead (Pb) mixed perovskite solar cells (PSCs) stand out as the optimal choice for the bottom subcell of the all-perovskite tandem solar cells. One of the major challenges impeding the further enhancement of Sn–Pb mixed PSCs power conversion efficiency (PCE) is the easy oxidation of Sn²⁺ to Sn⁴⁺ and a large number of Sn vacancies in the perovskite films. In this work, the sources of Sn²⁺ oxidation in the perovskite precursor solution are systematically investigated, focusing on the oxidation state of raw materials, solvent-dissolved oxygen, and solvent oxidizing ability. It is discovered that compared to the commonly used dimethyl sulfoxide (DMSO) solvent, N, N'-Dimethylpropyleneurea (DMPU) exhibits a weaker oxidizing ability while forming excellent coordination with the perovskite precursor. Using a mixed solvent of N, N-Dimethylformamide (DMF), and DMPU as the precursor solvent not only obviates the need for additional antioxidants but also demonstrates reduced oxidation susceptibility toward Sn–Pb mixed perovskite. Utilizing a gas-assisted technique without anti-solvents, high-efficiency Sn–Pb mixed PSCs are fabricated. These findings not only deepen the understanding of the oxidation phenomena in Sn–Pb perovskite precursor solutions but also provide essential guidance for the scalable production of Sn–Pb mixed PSCs and tandem solar cells.

Inverted perovskite solar cells (PSCs) have both excellent stability and continuously broken-through efficiencies. Herein, the characteristics of inverted PSCs including each functional layers, interfacial regulation strategies, and device stability are summarized. Meanwhile, the applications of inverted structure in tandem and flexible photovoltaic devices, and modules are introduced. Finally, the remaining challenges and several proposals of PSCs are put forward.

Abstract

Perovskite solar cells (PSCs) have attracted widespread research and commercialization attention because of their high power conversion efficiency (PCE) and low fabrication cost. The long-term stability of PSCs should satisfy industrial requirements for photovoltaic devices. Inverted PSCs with a p-i-n architecture exhibit considerable advantages because of their excellent stability and competitive efficiency. The continuously broken-through PCE of inverted PSCs shows huge application potential. This review summarizes the developments and outlines the characteristics of inverted PSCs including charge transport layers (CTLs), perovskite compositions, and interfacial regulation strategies. The latest effective CTLs, interfacial modification, and stability promotion strategies especially under light, thermal, and bias conditions are emphatically analyzed. Furthermore, the applications of the inverted structure in high-efficiency and stable tandem, flexible photovoltaic devices, and modules and their main obstacles are systematically introduced. Finally, the remaining challenges faced by inverted devices are discussed, and several directions for advancing inverted PSCs are proposed according to their development status and industrialization requirements.

This study explores the effect of side-chain polarity on organic solar cells (OSCs) performance by synthesizing two non-fullerene acceptors, ITIC-16F and ITIC-E. It shows that side-chain polarity influences component distribution within the photoactive layer, affecting excitation energy levels and charge transport. Incorporating ITIC-E significantly enhances power conversion efficiency to 19.4%, highlighting side-chain manipulation as a key strategy for OSC enhancement.

Abstract

Component distribution within the photoactive layer dictates the morphology and electronic structure and substantially influences the performance of organic solar cells (OSCs). In this study, a molecular design strategy is introduced to manipulate component and energetics distribution by adjusting side-chain polarity. Two non-fullerene acceptors (NFAs), ITIC-16F and ITIC-E, are synthesized by introducing different polar functional substituents onto the side chains of ITIC. The alterations result in different distribution tendencies in the bulk heterojunction film: ITIC-16F with intensified hydrophobicity aligns predominantly with the top surface, while ITIC-E with strong hydrophilicity gravitates toward the bottom. This divergence directly impacts the vertical distribution of the excitation energy levels, thereby influencing the excitation kinetics over extended time periods and larger spatial ranges including enhanced diffusion-mediated exciton dissociation and stimulated charge carrier transport. Benefitting from the favorable energy distribution, the device incorporating ITIC-E into the PBQx-TF:eC9-2Cl blend showcases an impressive power conversion efficiency of 19.4%. This work highlights side-chain polarity manipulation as a promising strategy for designing efficient NFA molecules and underscores the pivotal role of spatial energetics distribution in OSC performance.

Nature Communications, Published online: 02 March 2024; doi:10.1038/s41467-024-46144-8

Nature, Published online: 04 March 2024; doi:10.1038/s41586-024-07228-z

Nature, Published online: 04 March 2024; doi:10.1038/s41586-024-07226-1