Chen Weijie

The columnar liquid crystal (T6TE) is embedded into perovskite to in situ disperse the excess PbI₂. T6TE-assisted perovskite gains optimal crystallization and less defects with no aggregated PbI₂ crystals, achieving a prominent power conversion efficiency (PCE) of 24.27%. The PCE of the large-scale device (1 cm²) reaches to 21.50%.

Abstract

Excess PbI₂ has been deemed as indispensable component to boost the efficiency of perovskite solar cells (PSCs). However, the random aggregation of PbI₂ crystals seriously disturbs the transport behavior of the carrier and accelerates the degradation of perovskite film. Herein, an effective strategy to in situ disperse excess PbI₂ crystals via the columnar liquid crystal (T6TE) is developed. Rapid self-assembly induced by intermolecular π–π interaction enables T6TE to form the ordered columnar phase with “edge-on” orientation in perovskite. The columnar T6TE can efficiently disperse excess PbI₂ crystals with the merits of strong negative electrostatic potential and highly steric hindrance. Target perovskite deserves preferable crystallization and reconstructed surface, leading to reduced defects density, less residual stress, and efficient carrier transport. Besides, the T6TE significantly impedes the degradation of perovskite film and the formation of Pb⁰ defects. Resultant T6TE-assisted PSCs achieve the champion power conversion efficiency (PCE) of 24.27% for mixed Cs⁺-FA⁺-MA⁺ perovskite. The PCE of a larger area (1 cm²) device reaches to 21.50%. The unencapsulated device maintains ≈85% of the initial PCE after 1500 h storage in the atmosphere with 40–60% relative humidity. This work provides a new strategy to in situ disperse excess PbI₂ by incorporating columnar liquid crystal for the first time.

A conjugated phosphonic acid is developed to modify Spiro-OMeTAD benchmark HTL, leading to superior charge conductivity, reinforced ion immobilization, and remarkable device stability.

Abstract

High efficiency and long-term stability are the prerequisites for the commercialization of perovskite solar cells (PSCs). However, inadequate and non-uniform doping of hole transport layers (HTLs) still limits the efficiency improvements, while the intrinsic instability of HTLs caused by ion migration and accumulation is difficult to be addressed by external encapsulation. Here it is shown that the addition of a conjugated phosphonic acid (CPA) to the Spiro-OMeTAD benchmark HTL can greatly enhance the device efficiency and intrinsic stability. Featuring an optimal diprotic-acid structure, indolo(3,2-b)carbazole-5,11-diylbis(butane-4,1-diyl) bis(phosphonic acid) (BCZ) is developed to promote morphological uniformity and mitigate ion migration across both perovskite/HTL and HTL/Ag interfaces, leading to superior charge conductivity, reinforced ion immobilization, and remarkable film stability. The dramatically improved interfacial charge collection endows BCZ-based n-i-p PSCs with a champion power conversion efficiency of 24.51%. More encouragingly, the BCZ-based devices demonstrate remarkable stability under harsh environmental conditions by retaining 90% of initial efficiency after 3000 h in air storage. This work paves the way for further developing robust organic HTLs for optoelectronic devices.

Publication date: March 2024

Source: Nano Energy, Volume 121

Author(s): Fengwu Liu, Yongchao Ma, Yuanyuan Zhang, Eunhye Yang, Insoo Shin, Junpeng Xue, Fuqiang Li, Danbi Kim, Hyun-Seock Yang, Bo Ram Lee, Pesi Mwitumwa Hangoma, Sung Heum Park

3,4,5-trichlorobenzoic acid is first reported as the anode interfacial layer material, which can be facilely processed by air-blading (without annealing) and in situ self-assembly. Organic photovoltaics devices based on PM6: BTP-eC9 achieve an impressively high efficiency of 18.8% with in situ self-assembled 3,4,5-trichlorobenzoic acid anode interfacial layer, representing the highest value among devices with in situ self-assembly anode interfacial layer.

Abstract

Future industrialization of organic photovoltaics (OPVs) requires OPVs’ processing to be more energy-efficient and streamlined. Currently, only MoO₃ and PEDOT:PSS are commonly used as the anode interface layer (AIL). The processing of MoO₃ typically involves vacuum thermal evaporation with stringent thickness requirements. PEDOT:PSS necessitates separate processing and thermal annealing at temperatures exceeding 100 °C to eliminate moisture. This work utilized 3,4,5-trichlorobenzoic acid (3CBA) as the AIL material. The distinct advantage of 3CBA over PEDOT:PSS and MoO₃ is the in situ self-assembly of 3CBA eliminates the need for separate solution processing, thermal evaporation, or thermal annealing. Remarkably, OPV devices incorporating PM6, BTP-eC9, and the 3CBA AIL exhibited a superior efficiency of 18.2% compared to those with PEDOT:PSS (17.7%). By using nonhalogenated solvent, o-xylene, to meet industrialization requirements, the devices achieved an exceptional efficiency of 18.8%, the highest reported value among devices with in situ self-assembled interface layers. Furthermore, semi-transparent devices with 3CBA displayed higher PCE and AVT values (13.1% and 25.7%) than their PEDOT: PSS counterparts, due to the weak absorption of the 3CBA AIL. This work contributes significantly to the high-throughput production of OPVs by streamlining the AIL processing.

Quinoxaline and triphenylamine-based organic small molecules are designed to enhance the interfacial properties between the perovskite and the NiO_x hole transport layer in inverted-type wide-bandgap perovskite solar cells (PSCs). The integration of these organic interlayers effectively mitigates the energy level offset, passivates defects, and enhances the quality of the perovskite film. This improvement results in an outstanding efficiency of 20.1% for a 1.75 eV wide-bandgap PSC.

Abstract

Interfacial engineering in organic–inorganic hybrid perovskite solar cells (PSCs) has attracted significant attention, aiming to achieve high-performing and highly stable devices. Here, newly designed organic small molecules based on quinoxaline and triphenylamine for inverted type wide-bandgap PSCs are introduced, with the objective of enhancing the interfacial properties between perovskite and NiO_x hole transport layer (HTL). The incorporation of an organic interlayer effectively reduces the energy level offset between the HTL and wide-bandgap perovskite, while passivating defects within the perovskite layer. It leads to improved charge extraction and minimized non-radiative recombination at the interface. Furthermore, the enhanced interfacial characteristics and hydrophobicity contribute to the improvement of perovskite film quality, resulting in larger grain size and higher crystallinity. As a result, the power conversion efficiency (PCE) of the PSC is enhanced from 18.9% to 20.1% with the incorporation of the IQTPAFlu interlayer, accompanied by an increase in V _oc to ≈1.3 V, achieving a significantly low V _oc deficit of 0.46 V. And the IQTPAFlu-based devices demonstrate stable and consistent performance over 500 h, with ≈91% of their initial PCE retained. The highly stable wide-bandgap PSCs, characterized by high V _oc and PCEs, hold great promise as potential candidates for tandem solar cells.

A novel solid additive-assisted selective optimization strategy for sequential-deposited active layers is successfully developed to synergistically optimize absorption, crystallinity, charge transport, and phase separation. Therefore, the binary OSCs obtained an impressive high efficiency over 19% with less energy loss/disorder and faster hole-transfer.

Abstract

Volatile solid (VS)-additives are regarded as an effective tool to manipulate morphology of sequential deposited (SD) active layers for improving power conversion efficiencies (PCEs) of organic solar cells (OSCs), while the independent effect of VS-additives on donor and acceptor layers is often overlooked. Herein, a new VS-additive named 2-(2-methoxyphenyl)benzo[b]thiophene (BTO) is synthesized and applied in SD binary PM6/L8-BO active layers. Introducing it into bottom PM6 layer (PM6⁺), BTO has a low volatility and longer volatilization distance, which prolongs the interaction time between BTO and L8-BO in PM6⁺/L8-BO film, leading to an over-aggregated L8-BO. While inserting it into top L8-BO layer (L8-BO⁺), the fast evaporation of BTO and excellent dipole interaction between BTO and L8-BO help to enhance molecular absorption, crystallinity, and ordered packing of PM6/L8-BO⁺ system. Therefore, an optimized morphology with proper phase separation is achieved to increase exciton dissociation and charge transfer properties, restrain charge recombination and energy loss of OSCs, yielding an impressive PCE of over 19%. Furtherly, using D18 instead of PM6, binary SD-systems offer a record-high PCE of 19.16%. The developed selective optimization strategy for SD active layers provides a deep insight into the working mechanism of VS-additives for boosting PCE of OSCs.

In-plane directional crystallization of perovskite is realized by inducing a horizonal solvent vapor pressure gradient atop the wet film with the built tiny chamber. Perovskite of high crystallinity with obvious growth orientation is thus well filled in the non-ordered mesoporous scaffold, and boosts the PCE of the printable hole-conductor-free carbon-based perovskite solar cell and module to 19.35% and 16.53%.

Abstract

Popular solution-processed approaches for producing the active layer of perovskite solar cells (PSCs) generally have to make compromise between crystallinity and compactness by inducing a rapid crystallization process with explosive nucleation and limited growth via removing solvent quickly. Here, a practical growth-dominated in-plane directional crystallization technique (IPDC) with a deeply retarded crystallization process for the scalable preparation of PSCs are reported. During the low-temperature annealing, a tiny chamber with a small height is built atop the wet perovskite precursor film to restrain the vertical diffusion and removal of solvent vapor. The chamber eliminates the vertical solvent vapor gradient and induce a horizonal in-plane gradient of solvent vapor pressure (SVP) toward the preset exhaust port which allows the slow escape of solvent vapor to outer space. In this way, nucleation is induced preferentially near the port and the as-formed heterogeneous nuclei then grow continuously and directionally. With IPDC, sufficient filling of perovskite with high crystallinity and obvious growth orientation is realized in non-ordered mesoporous scaffolds. An encouraging power conversion efficiency of 19.35% and 16.53% is achieved respectively for the 0.1 and 52.3-cm² printable mesoscopic hole-conductor-free PSCs with carbon electrodes.

A novel intermediate phase modification (IPM) strategy is developed to effectively repair grain boundaries in the CsPbI₃ type perovskite microcrystalline thin film, while simultaneously creating patches for interconnecting these boundaries. The resultant CsPbI₃ solar cells exhibit a power conversion efficiency of ≈20% and exceptional shelf stability, enduring 3000 h of exposure to air without encapsulation.

Abstract

The presence of excess secondary-phase PbI₂ in perovskite films shows a negative impact on their long-term stability. Herein, an intermediate phase modification (IPM) strategy is proposed to eliminate residual PbI₂ for improved quality of all-inorganic CsPbI₃-type perovskite films, wherein the extrinsic agent is introduced to address the intermediate phase. By transforming residual PbI₂ into a novel 1D perovskite phase, the IPM strategy acts as a patch to suture grain boundaries in the inorganic perovskite films. In addition, the IPM strategy not only enhances the quality of perovskite films but also mitigates energy disorder, reduces trap state density, and prolongs carrier lifetime by expediting the intermediate phase conversion process and passivating surface defects. As such, the perovskite solar cells (PSCs) with a high power conversion efficiency (PCE) of ≈20% and a high fill factor of 83.3% are considered to be very efficient, with excellent shelf stability of 3000 h of exposure in air without any encapsulation. This work not only exhibits a novel optimization route for inorganic perovskite but also emphasizes the crucial role of eliminating residual PbI₂ in inorganic perovskites.

A porous insulating layer (PIL) made of self-assembled diphenylphosphinic acid (DPPA) is fabricated atop a perovskite film to address the challenge of balancing defect passivation and charge transport. Entire surface of perovskite film is well-passivated and energy level is modulated with DPPA treatment, and surplus DPPA forms PIL with submicrometer-scale openings, providing efficient charge transport pathways. The methylammonium-free perovskite devices with PIL structures exhibit enhanced efficiency and operational stability.

Abstract

In recent years, the surface modification of perovskite by wide band-gap insulating materials has been one of the main strategies to achieve efficient and stable perovskite solar cells (PSCs). Unfortunately, a significant hurdle in this approach is the dilemma surrounding the quality of passivation and the transport of charges. Here, this trade-off is overcome by introducing self-assembled diphenylphosphinic acid (DPPA) porous layer. Applying highly concentrated DPPA solution on the perovskite surface not only provides excellent passivation of entire surface, but also the excess DPPA will form a self-assembled porous insulating layer (PIL), which forms random submicron-sized openings at the interface of the insulating layer for accelerated charge transport. In addition, the energy level of the perovskite surface can be modulated by this insulating material to facilitate carrier transport. As a result, an impressive power conversion efficiency (PCE) over 24% has been achieved in methylammonium-free p-i-n devices with an ultrahigh fill factor (FF) of 84.7%. The unencapsulated devices exhibit excellent thermal and operational stability. This work paves a way for establishment of an effective passivation and facilitated transport simultaneously.

Nature Communications, Published online: 22 December 2023; doi:10.1038/s41467-023-44235-6

Practical thermal atomic layer deposition (ALD) of NiO for hole-transporting layer is demonstrated using hydrogen peroxide (h-NiO) and ozone (o-NiO) as oxidants. Inverted perovskite solar cells based on ALD-NiO with power conversion efficiency of 18.5% (h-NiO) and 19.7% (o-NiO) fabricate and clarify the importance of oxidation power of oxidant during ALD for p-type oxide deposition.

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has significantly improved through advancements in fabrication methods, which have primarily focused on the perovskite absorber layer. The significance of improving the charge transport layer as the next crucial step toward achieving highly stable and efficient PSCs has also been emphasized. In inverted PSCs (i-PSCs), the selection of a suitable p-type hole-transporting layer (HTL) has been restricted to mainly organic materials due to the rarity of p-type inorganics. The instability and inherent disadvantages of organics necessitate the use of stable p-type oxides as HTLs for i-PSCs. Herein, uniform, conformal, and practical, yet thermal atomic layer deposition (ALD) for NiO is demonstrated by employing two different oxidant, ozone (O₃) and hydrogen peroxide (H₂O₂). Both ALD-NiO films are characterized by X-ray diffraction and X-ray reflection. By conducting X-ray photoelectron spectroscopy analysis of the ALD-NiO surfaces, a correlation between the oxidation power of the oxidant during ALD and the surface oxidation state of the ALD-NiO films is established. Finally, the relationship between the oxidation state of the surfaces with different oxidant and the i-PSC performance is verified. The fabricated i-PSCs exhibit a PCE exceeding 19%.

We synthesized poly(ionic liquid)s to craft a hydrophobic hydrogen-bonded polymer network that passivates the wide-band gap perovskite/electron transport layer interface and inhibits ion migration. The optimized devices achieve impressive efficiencies with outstanding thermostability and humidity resistance. The textured perovskite/Si tandem cell also reaches a remarkable champion efficiency maintaining exceptional operational stability.

Abstract

The pursuit of highly efficient and stable wide-band gap (WBG) perovskite solar cells (PSCs), especially for monolithic perovskite/silicon tandem devices, is a key focus in achieving the commercialization of perovskite photovoltaics. In this study, we initially designed poly(ionic liquid)s (PILs) with varying alkyl chain lengths based on density functional theory calculations. Results pinpoint that PILs with longer alkyl chain lengths tend to exhibit more robust binding energy with the perovskite structure. Then we synthesized the PILs to craft a hydrophobic hydrogen-bonded polymer network (HHPN) that passivates the WBG perovskite/electron transport layer interface, inhibits ion migration and serves as a barrier layer against water and oxygen ingression. Accordingly, the HHPN effectively curbs nonradiative recombination losses while facilitating efficient carrier transport, resulting in substantially enhanced open-circuit voltage (V _oc) and fill factor. As a result, the optimized single-junction WBG PSC achieves an impressive efficiency of 23.18 %, with V _oc as high as 1.25 V, which is the highest reported for WBG (over 1.67 eV) PSCs. These devices also demonstrate outstanding thermostability and humidity resistance. Notably, this versatile strategy can be extended to textured perovskite/silicon tandem cells, reaching a remarkable efficiency of 28.24 % while maintaining exceptional operational stability.

Recent advancements in scalable coating methods for perovskite solar modules (PSMs) are reviewed. The report explores the fundamental aspects of scalable deposition techniques, detailing the merits and demerits of each method. It encompasses the ongoing progress in the performance and operational stability of PSMs. The review aims to offer insights into large-area perovskite coatings for stable and efficient PSMs.

The technological requirements are changing, and there is a push for more effective energy production and conversion technologies as a result of a social desire for sustainable and renewable energy sources. Solar energy conversion, particularly photovoltaic cells, offers a potentially helpful solution in this situation. Power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been reported to have increased significantly from 3% to 26.1%. The transition from laboratory PSCs to their commercialization needs scalable deposition techniques, high efficiency at a scalable level, and perovskite photovoltaic with minimal loss in PCE. In this review article, the scalable fabrication processes for perovskite solar modules (PSMs) and their fabrication challenges, as well as latest developments in PSM stability, are focused on. Finally, the future prospectus and challenges for PSMs are presented. This review will give us an overall understanding of the thin film coating inside the PSM and good insight into the future direction of development.

Nature Energy, Published online: 19 December 2023; doi:10.1038/s41560-023-01432-3

By introducing a novel 2D Eu-TCPP MOF between the perovskite layer and carbon electrode, the photoresponse and stability of MAPbI₃ are significantly improved, and the redox effect prolongs the device's life. Ultimately benefiting from the synergistic effect, the assembled carbon-based perovskite solar cells (C-PSCs) have achieved a champion efficiency of 18.13%.

Abstract

The low power conversion efficiency (PCE) of hole transport materials (HTM) – free carbon-based perovskite solar cells (C-PSCs) poses a challenge. Here, a novel 2D Eu-TCPP MOF (TCPP; [tetrakis (4-carboxyphenyl) porphyrin]) sandwiched between the perovskite layer and the carbon electrode is used to realize an effective and stable HTM-free C-PSCs. Relying on the synergistic effect of both the metal-free TCPP ligand with a unique absorption spectrum and hydrophobicity and the EuO₄(OH)₂ chain in the Eu-TCPP MOF, defects are remarkably suppressed and light-harvesting capability is significantly boosted. Energy band alignment is achieved after Eu-TCPP MOF treatment, promoting hole collection. Förster resonance energy transfer results in improved light utilization and protects the perovskite from decomposition. As a result, the HTM-free C-PSCs with Eu-TCPP MOF reach a champion PCE of 18.13%. In addition, the unencapsulated device demonstrates outstanding thermal stability and UV resistance and keeps 80.6% of its initial PCE after 5500 h in a high-humidity environment (65%–85% RH).

Ionic coupling potassium sorbate with perovskite controls the formation of N-methyl formamidinium ions, which passivate defects and freeze halide segregation in perovskite films under intense light. Target single-junction wide-bandgap perovskite solar cells achieved a record efficiency of 22.00% with photostability of less than 2% decay over 2000 h of operation. Perovskite/TOPCon silicon tandem solar cells achieved an efficiency of 30.72%.

Abstract

Photo-induced halide segregation in wide-bandgap (WBG) perovskite leads to poor stability and limits its application in high-efficiency tandem solar cells. Here, a simple solution strategy to achieve photostable WBG perovskite solar cells (PSCs) with bandgap of ≈1.67 eV by ionic coupling potassium sorbate with defects at the buried perovskite interface is reported. Moreover, the ionic coupled potassium sorbate (ICPS) enables to control the formation of N-methyl formamidinium ions that can selectively passivate the perovskite defects at grain boundaries. As a result, the photo-induced halide segregation in the target perovskite films is frozen under intense light. The target single-junction WBG PSC achieves a record efficiency of 22.00% with an open-circuit voltage (V _OC) of 1.272 V and photostability of less than 2% decay over 2000 h of operation. Perovskite/Silicon tandem solar cells are also fabricated that achieve an efficiency of 30.72% (certified 30.09% @1.087 cm²), which is the highest efficiency reported to date with a tunneling oxide passivating contact (TOPCon) c-Si substrate. The encapsulated tandem device can maintain 97% of its initial efficiency after 1000 h of operation.

Publication date: March 2024

Source: Nano Energy, Volume 121

Author(s): Ming Luo, Sanlong Wang, Zhao Zhu, Biao Shi, Pengyang Wang, Guofu Hou, Qian Huang, Ying Zhao, Xiaodan Zhang

Publication date: March 2024

Source: Nano Energy, Volume 121

Author(s): Mengmeng Yuan, Hongru Ma, Qingshun Dong, Xiuyun Wang, Linghui Zhang, Yanfeng Yin, Zhehan Ying, Jingya Guo, Wenzhe Shang, Jie Zhang, Yantao Shi

Leveraging the inherent rigidity of molecular structural units and robust intermolecular π–π stacking interactions, PTCDI-C₈ molecules demonstrate a vertically aligned orientation on substrates, yielding an elevated thermal conductivity of 3.1 ± 0.1 W m⁻¹ K⁻¹. Through a combination of TDTR, nanoindentation, and molecular dynamics simulations, it is ascertained that the significant Young's modulus of PTCDI-C₈ is the primary contributor to its high thermal conductivity.

Abstract

Attaining elevated thermal conductivity in organic materials stands as a coveted objective, particularly within electronic packaging, thermal interface materials, and organic matrix heat exchangers. These applications have reignited interest in researching thermally conductive organic materials. The understanding of thermal transport mechanisms in these organic materials is currently constrained. This study concentrates on N, N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈), an organic conjugated crystal. A correlation between elevated thermal conductivity and augmented Young's modulus is substantiated through meticulous experimentation. Achievement via employing the physical vapor transport method, capitalizing on the robust C═C covalent linkages running through the organic matrix chain, bolstered by π–π stacking and noncovalent affiliations that intertwine the chains. The coexistence of these dynamic interactions, alongside the perpendicular alignment of PTCDI-C₈ molecules, is confirmed through structural analysis. PTCDI-C₈ thin film exhibits an out-of-plane thermal conductivity of 3.1 ± 0.1 W m⁻¹ K⁻¹, as determined by time-domain thermoreflectance. This outpaces conventional organic materials by an order of magnitude. Nanoindentation tests and molecular dynamics simulations elucidate how molecular orientation and intermolecular forces within PTCDI-C₈ molecules drive the film's high Young's modulus, contributing to its elevated thermal conductivity. This study's progress offers theoretical guidance for designing high thermal conductivity organic materials, expanding their applications and performance potential.

2D BA₂PbI₄ perovskite seeds are employed to modulate the nucleation and enhance the crystallization of the PbI₂ film, the high-crystalline PbI₂ film has facile and adequate reaction with the ammonium salts and can be converted rapidly into α-phases perovskite. This helps to achieve perovskite solar cells with 24.3% efficiency and excellent stability.

Abstract

Using seeds to control the crystallization of perovskite film is an effective strategy for achieving high-efficiency perovskite solar cells (PSCs). Owing to their excellent environmental stability brought by their long alkyl chain, n-butylammonium (BA) cations are widely used for fabricating efficient and stable PSCs. However, BA-based 2D perovskite is seldom been investigated as a seed. Here, BA₂PbI₄ is employed to regulate the crystallization of PbI₂, acting as nucleation centers. As a result, porous PbI₂ film with high crystallinity is obtained, which allows the realization of perovskite film with preferential crystal orientations of (001) and large grain size of over 2 µm. The corresponding PSC achieves a high power conversion efficiency (PCE) of 24.30% and exhibits satisfactory stability, retaining 91.70% of the initial PCE after 300 h of thermal aging at 85°C.

A novel organic dye molecule PDINN-S is employed to dope and suppress the detrimental catalytic activity of ZnO electron transport layer, thereby simultaneously enhance the efficiency and photo-stability of the inverted non-fullerene OSCs.

Abstract

The solution-processed zinc oxide (ZnO) electron transport layer (ETL) always exhibits ubiquitous defects, and its photocatalytic activity is detrimental for the organic solar cell (OSC) to achieve high efficiency and stability. Herein, an organic dye molecule, PDINN-S is introduced, to dope ZnO, constructing a hybrid ZnO:PDINN-S ETL. This hybrid ETL exhibits improved electron mobility and conductivity, particularly post-light exposure. The catalytic activity of ZnO is also effectively suppressed.Consequently, the efficiency and photo-stability of inverted non-fullerene OSCs are synergistically enhanced. The devices based on PM6:Y6/PM6:BTP-eC9 active layer with ZnO:PDINN-S as ETL give impressive power conversion efficiencies (PCEs) of 16.78%/17.59%, significantly higher than those with pure ZnO as ETL (PCEs = 15.31%/16.04%). Moreover, ZnO:PDINN-S-based device shows exceptional long-term stability under continuous AM 1.5G illumination (T ₈₀ = 1130 h) , overwhelming the reference device (T ₈₀ = 455 h). In addition, Incorporating PDINN-S into ZnO alleviate mechanical stress within the inorganic lattice, making ZnO:PDINN-S ETL more suitable for the fabrication of flexible devices. Overall, doping ZnO with organic dye molecules offers an innovative strategy for developing multifunctional and efficient hybrid ETL of the non-fullerene OSCs with excellent efficiency and photo-stability.

A novel solvent additive is proposed to enhance the ordered donor–acceptor crystallization for improving the performance of polymer solar cells. This study offers a new perspective on the mechanism underlying the function of solvent additives and presents a comprehensive research methodology that will guide the development for efficient polymer solar cells.

Abstract

Controlled sequential crystallization of donors and acceptors is a critical factor for achieving enhanced phase separation and efficient charge transfer performance in polymer solar cells (PSCs). In this study, a comprehensive investigation of a structurally simple solvent additive, 1-fluoro-2-iodobenzene (OFIB) is conducted, which efficiently controls the morphology of the active layer, resulting in fibrous assembly and significantly enhancing the power conversion efficiency from 16.34% to 18.38% based on the PM6:L8-BO system. Density functional theory, molecular dynamics simulations, and grazing incidence small- and wide-angle X-ray scattering techniques reveal that the addition of OFIB to the processed blend aligns the orientation of the acceptor molecules, thereby enhancing the overall π–π stacking in the active layer. OFIB establishes nearly equal-strength π–π interactions with the conjugated frameworks of both the donor and acceptor materials, benefiting from the multiple electron conjugation between its iodine atom and the conjugated framework in the active layer. Femtosecond-timescale photophysical studies demonstrate that the OFIB-optimized active layer shows reduced exciton losses at the donor–acceptor interface. This study offers a new perspective on the mechanism underlying the function of solvent additives and presents a comprehensive research methodology that will guide the development of next-generation non-fullerene acceptors for efficient PSCs.