Chen Weijie

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part B

Author(s): Ling Bai, Zhibin Yu, Le Liu, Yilin Chang, Zhiwei Ma, Tonggang Jiu

The diluted layer-by-layer (N-LBL) strategy is employed to fabricate all-polymer solar cells (all-PSCs). Such film-forming strategy combined the advantage of traditional bulk-heterojunction and LBL methods, and thus exhibited suitable donor–acceptor interfaces and optimal photon utilization behaviors. Consequently, a high short-circuit current density over 26 mA cm⁻² and promising power conversion efficiencies of 18.33% are realized for N-LBL prepared all-PSCs.

Abstract

Disordered polymer chain entanglements within all-polymer blends limit the formation of optimal donor–acceptor phase separation, and thus the performance of all-polymer organic solar cells (all-PSCs). Considering the challenge and importance of morphology regulation in all-PSCs, a diluted layer-by-layer (N-LBL) strategy is thereby adopted to fine-tuning the properties of all-polymer blends. When comparing the traditional PM6:PY-IT based bulk-heterojunction (BHJ) film and PM6/PY-IT layer-by-layer (LBL) film, the N-LBL film, which is prepared from diluted PM6 (with 3% PY-IT) bottom layer and diluted PY-IT (with 6% PM6) top layer, displayed a clearer bi-continuous fibrillar network and a higher exciton generation process. Benefiting from these unique characters, the all-PSC consisting the N-LBL active layer exhibited a short-circuit current density over 26 mA cm⁻² and a power conversion efficiency (PCE) of 18.33%, which are both higher than those of BHJ (16.88%) and LBL (17.13%) devices. Moreover, the universality of the dilution strategy in other all-polymer blends (PM6 and PY-DT, PM6 and PY-FT-o) is also demonstrated with unanimously improved device performance. This work underscores the effectiveness of the diluted layer-by-layer method in tuning the morphologies and charge dynamics for high-performance all-PSCs.

Based on two developed biaxial-conjugated NFAs with varied side-chain symmetry, the side-chain symmetry of NFAs is directly correlated with the exciton delocalization and triplet dynamics in OSCs. The symmetric NFA having diverse molecular packing orientations can form multiple charge transfer channels and a slower rate of spin-triplet state, resulting in a much lower non-radiative voltage loss.

Abstract

The structural revolutions of non-fullerene acceptors (NFAs) have driven continuous efficiency breakthroughs in organic solar cells (OSCs). Rational regulation of NFA structures toward efficient exciton dissociation and mitigated non-radiative recombination is pivotal for OSCs. The incorporation of asymmetric side chains on NFAs can often achieve these goals by inducing a desirable aggregate state. However, it lacks the studies to directly correlate the side-chain symmetry of NFAs with the exciton delocalization and triplet dynamics in OSCs. Herein, The influence of structural symmetry on the aggregate properties is systematically investigated and exciton/charge dynamics based on two developed biaxial-conjugated NFAs with varied side-chain symmetry. The symmetric NFA having diverse molecular packing orientations can form multiple charge transfer channels in its blend with polymer donor, which cannot be found in that comprising the asymmetric ones. Moreover, a slower rate and lower ratio of the spin-triplet state are formed in the blend of symmetric NFA, resulting in a much lower non-radiative voltage loss in corresponding OSCs. This study reveals the distinct advantages of symmetric NFAs in both aggregate properties and exciton/charge dynamics over those of asymmetric ones, paving the way for developing high-performance OSCs using easier-to-prepare, low-cost symmetric materials.

This review delves into the pivotal role of hole transport layers (HTLs) in improving the efficiency and stability of Sn-Pb perovskite solar cells (PSCs). It discusses the unique challenges HTLs face in Sn-Pb PSCs, reviews recent advances in organic, inorganic, SAM, and HTL-free designs, and highlights key factors and future directions for optimizing HTLs to achieve high-performance devices.

Abstract

Hybrid organic–inorganic lead halide perovskite solar cells (PSCs) have rapidly emerged as a promising photovoltaic technology, with record efficiencies surpassing 26%, approaching the theoretical Shockley-Queisser limit. The advent of all-perovskite tandem solar cells (APTSCs), integrating Pb-based wide-bandgap (WBG) with mixed Sn-Pb narrow-bandgap (NBG) perovskites, presents a compelling pathway to surpass this limit. Despite recent innovations in hole transport layers (HTLs) that have significantly improved the efficiency and stability of lead-based PSCs, an effective HTL tailored for Sn-Pb NBG PSCs remains an unmet need. This review highlights the essential role of HTLs in enhancing the performance of Sn-Pb PSCs, focusing on their ability to mitigate non-radiative recombination and optimize the buried interface, thereby improving film quality. The distinct attributes of Sn-Pb perovskites, such as their lower energy levels and accelerated crystallization rates, necessitate HTLs with specialized properties. In this study, the latest advancements in HTLs are systematically examined for Sn-Pb PSCs, encompassing organic, self-assembled monolayer (SAM), inorganic materials, and HTL-free designs. The review critically assesses the inherent limitations of each HTL category, and finally proposes strategies to surmount these obstacles to reach higher device performance.

The recent progress of negative capacitance (NC) field effect transistors (FETs) with ferroelectric gate stack is summarized in this review, including the related concepts for in-depth understanding of NC FETs. Moreover, some high-performance NC FETs with different ferroelectric gate stacks are presented. Finally, influential factors and challenges for improving 2D NC FETs are proposed.

Abstract

Steep subthreshold swing (SS) is a decisive index for low energy consumption devices. However, the SS of conventional field effect transistors (FETs) has suffered from Boltzmann Tyranny, which limits the scaling of SS to sub-60 mV dec⁻¹ at room temperature. Ferroelectric gate stack with negative capacitance (NC) is proved to reduce the SS effectively by the amplification of the gate voltage. With the application of 2D ferroelectric materials, the NC FETs can be further improved in performance and downscaled to a smaller dimension as well. This review introduces some related concepts for in-depth understanding of NC FETs, including the NC, internal gate voltage, SS, negative drain-induced barrier lowering, negative differential resistance, single-domain state, and multi-domain state. Meanwhile, this work summarizes the recent advances of the 2D NC FETs. Moreover, the electrical characteristics of some high-performance NC FETs are expressed as well. The factors which affect the performance of the 2D NC FETs are also presented in this paper. Finally, this work gives a brief summary and outlook for the 2D NC FETs.

The pseudo-planar heterojunction (PPHJ) structure fabricated by sequential deposition process can successfully improve vertical phase separation. The devices based on PPHJ can suppress charge recombination and increase carrier transportation compared with integrated perovskite/bulk heterojunction solar cells, which also extend the near-infrared spectral absorption of devices up to 920 nm and obtain a champion efficiency of 23.25%.

Abstract

Broadening near-infrared (NIR) spectral response by virtue of organic bulk heterojunction (BHJ) is intensively explored to enhance power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the complex photovoltaic morphology and undesirable conductivity in BHJ structure can lead to the severe loss of photovoltaic performance, which are still urgent challenges for the commercialization of integrated PSCs (IPSCs). Recently, the gradual development of pseudo-planar heterojunction (PPHJ) structure with excellent vertical phase separation and improved charge transfer can hopefully provide more opportunities for IPSCs. Herein, an optimization strategy is reported employing PPHJ structure with hydrophobic long alkyl chains as the NIR light-absorbing layer in the devices, with which the light response of the IPSCs is extended to 920 nm. Owing to the lone electron pairs in the sulfur atoms, D18-Cl has functioned as an effective additive that can effectively modulate the growth of the perovskite and passivate the defects. As a result, the optimized device has achieved an impressive PCE of 23.25%, while the short-circuit current is enhanced from 22.93 to 25.14 mA cm⁻². The long-term and humidity stability of integrated perovskite/PPHJ solar cells are significantly elevated compared with IPSCs based on BHJ.

The graph illustrates the innovative approach of incorporating a sunscreen ingredient octinoxate (OCT) into perovskite structure. The OCT molecules passivate the defects in perovskite and improve solar cell performance. The OCT molecules, known for their UV resistance, effectively absorb UVB radiation and mitigate the detrimental effects of UV light on perovskite films, therefore leading to enhanced UV stability in perovskite solar cells.

Abstract

UV radiation presents a substantial challenge to the stability of perovskite solar cells (PSCs), limiting their applications in harsh environments such as outer space. Herein, UV-resistant molecule octinoxate (OCT) is introduced to mitigate the adverse effects of UV irradiation. OCT additive demonstrates the capability to modulate the crystallization process, resulting in perovskite films with larger grains and enhanced crystallinity. Moreover, OCT doping also facilitates charge extraction in PSCs. The PSCs with OCT doping exhibit an enhanced efficiency, increasing from 22.46% to 24.64%, along with improved stability with a T ₈₅ of 1000 h under continuous light exposure. Functioning as a sunscreen material, OCT mitigates UV-induced degradation by absorbing irradiation and hindering I₂ escape. Even after continuous exposure to 18.7 kWh m⁻² UV illumination, the OCT-doped PSCs maintain over 92% of their initial efficiency, meeting the 15 kWh m⁻² UV exposure requirement specified in the IEC:61215 PV robustness testing standard. This study offers a straightforward approach to enhance the durability of PSCs under UV radiation, opening avenues for their application in extreme environments.

In the process of fabricating large-area organic solar modules by blade-coating, solid additives effectively suppress the Marangoni flow caused by the surface tension gradient of liquid additives, resulting in a homogeneous active layer film and achieving an efficiency of 15.34% with respect to a total module area of 18.9 cm².

Abstract

Although encouraging progress in spin-coated small-area organic solar cells (OSCs), reducing efficiency loss caused by differences in film uniformity and morphology when up-scaled to large-area modules through meniscus-guided coating is an important but unsolved issue. In this work, in-depth research is conducted on the influence of both liquid and solid additives on the film uniformity and morphology of active layer in blade-coated PM6:L8-BO binary system. The study reveals that high boiling point liquid additives like 1,8-diiodooctane (DIO) used in blade-coating not only delay the volatilization of the solvent but also trigger the Marangoni flow in the same direction as capillary flow, causing excessive aggregation of acceptors, therefore destroying device performance. On the contrary, the solid additive 2-Iododiphenyl ether (IDPE), which is first reported in this work, can preserve the mechanism for improving device performance while effectively suppressing the excessive aggregation of acceptors during the film-forming process in blade-coating from halogen-free solvent of toluene, resulting in highly homogeneous large-area active layer films. Consequently, organic solar modules with an impressive efficiency of 15.34% with a total module area of 18.90 cm² via blade-coating based on PM6:L8-BO are achieved. This study not only provides a deep understanding on the effect of liquid and solid additives during blade-coating from the perspective of fluid mechanisms but also gives a pathway for the development of green solvent printed high-efficiency OSCs.

The impact of different synthetic protocols of block copolymer (BCP) is first investigated on the relevant photovoltaic properties. The more phase pure direct synthesis BCP exhibits enhanced intramolecular hole transfer, leading to a record efficiency of over 15% for single-material–organic solar cells together with excellent long-term operational stability.

Abstract

Recent studies on narrow bandgap all-conjugated block copolymer (BCP) single-material–organic solar cells (SMOSCs) have made unprecedented progress in power conversion efficiency (PCE); however, it still lacks understanding of the structure-property relationship in these highly mixed materials. Herein, the impact of different synthetic protocols (direct synthesis (d-BCP) versus sequential synthesis (s-BCP)) is first investigated on the relevant photovoltaic properties. Targeting the same BCP, namely PBDB-T-b-PYIT, it is found that the change in polymerization reaction leads to quite different optical and transport properties. The d-BCP outputs a record-high PCE of 15.02% for SMOSCs as well as enhanced operation stability under simulated 1-sun illumination, which is significantly higher than that of s-BCP (10.33%) and even close to its bulk heterojunction (BHJ) counterparts. Detailed transient absorption spectroscopy reveals ultrafast dynamics of charge transfer (CT) and exciton dissociation in BCP. In together with morphology characterization, it is revealed that the d-BCP has more phase pure composition, enhanced molecular ordering, and higher intramolecular CT efficiency relative to those of s-BCP. These findings gain insight into both the structure and carrier dynamic of BCP and demonstrate the possibility of achieving high-efficiency and stable SMOSCs.

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part B

Author(s): Xuping Liu, Chunyan Deng, Jihuai Wu, Lina Tan, Deng Wang, Zhang Lan, Qinghua Li

This work developshighly efficient perovskite/organic tandem solar cells (POTSC) via the simultaneous optimization of quaternary organic BHJ blend, and reduction of optical and electrical losses of interconnecting layers via self-assembly monolayer. The resultant POTSCs achieve a remarkable power conversion efficiency (PCE) of 25.56% (certified: 24.65%), with a record fill factor (FF) of 83.62% of all types of perovskite-based tandem solar cells (TSCs) till now.

Abstract

Perovskite/organic tandem solar cells (POTSCs) have garnered significant attention due to their potential for achieving high photovoltaic (PV) performance. However, the reported power conversion efficiencies (PCEs) and fill factors (FFs) are still subpar due to the challenges associated with charge extraction in the organic bulk-heterojunction (BHJ) and significant energy losses in the interconnecting layers (ICLs). Here, a quaternary organic BHJ blend is developed to enhance the charge extraction in the organic subcell, contributing to an increased FF of ≥78% under 1 sun illumination and even more under lower illumination intensities. Meanwhile, energy losses in the ICLs are reduced via the incorporation of a self-assembly monolayer (SAM), (4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz), in organic BHJ to form a MoO_x/SAM interface and the thorough control of the MoO _x thickness to suppress parasitic absorption. The resultant POTSCs achieve a remarkable PCE of 25.56% (certified: 24.65%), with a record FF of 83.62%, which is among the highest PCEs of POTSCs and the highest FF of all types of perovskite-based tandem solar cells (TSCs) till now. This work proves the optimization of charge extraction and ICLs are effective strategies to promote the performance of POTSCs to surpass other solution-processed perovskite-based TSCs in the near future.

The traditional hole transport material (HTM) PEDOT: PSS is a bottleneck for long-term stability in Sn–Pb perovskite solar cells (PSCs). This work offers an alternative means toward efficient and stable Sn–Pb PSCs using a new multi-functional HTM Silole-COOH, demonstrating 23.2%-efficient single-junction Sn–Pb PSCs, 25.8%-efficient all-perovskite tandems while avoiding the stability concerns associated with PEDOT: PSS.

Abstract

Despite high theoretical efficiencies and rapid improvements in performance, high-efficiency ≈1.2 eV mixed Sn–Pb perovskite solar cells (PSCs) generally rely on poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT: PSS) as the hole transport layer (HTL); a material that is considered to be a bottleneck for long-term stability due to its acidity and hygroscopic nature. Seeking to replace PEDOT: PSS with an alternative HTL with improved atmospheric and thermal stability, herein, a silole derivative (Silole-COOH) tuned with optimal electronic properties and efficient carrier transport by incorporating a carboxyl functional group is designed, which results in an optimal band alignment for hole extraction from Sn–Pb perovskites and robust air and thermal stability. Thin films composed of the Silole-COOH exhibit superior conductivity and carrier mobility compared to PEDOT: PSS, in addition to reduced nonradiative quasi-Fermi-level splitting losses at the HTL/perovskite interface and improved quality of Sn–Pb perovskite. Replacement of PEDOT: PSS with Silole-COOH leads to 23.2%-efficient single-junction Sn–Pb PSCs, 25.8%-efficient all-perovskite tandems, and long operating stability in ambient air.

In this work, the Ala-complexed NiO suppresses interfacial non-radiative recombination, improves the perovskite layer quality, and provides more favorable energy band alignment with the perovskite, resulting in improved charge transfer and reduced recombination. The incorporation of the Ala-complexed NiO leads to a power conversion efficiency (PCE) of 20.27% with enhanced stability under various conditions.

Abstract

The interface between NiO and perovskite in inverted perovskite solar cells (PSCs) is a major factor that can limit device performance due to defects and inappropriate redox reactions, which cause nonradiative recombination and decrease in open-circuit voltage (VOC). In the present study, a novel approach is used for the first time, where an amino acid (glycine (Gly), alanine (Ala), and aminobutyric acid (ABA))-complexed NiO are used as interface modifiers to eliminate defect sites and hydroxyl groups from the surface of NiO. The Ala-complexed NiO suppresses interfacial non-radiative recombination, improves the perovskite layer quality and better energy band alignment with the perovskite, resulting in improved charge transfer and reduced recombination. The incorporation of the Ala-complexed NiO leads to a PCE of 20.27% with enhanced stability under the conditions of ambient air, light soaking, and heating to 85 °C, as it retains over 82%, 85%, and 61% of its initial PCE after 1000, 500, and 350 h, respectively. The low-temperature technique also leads to the fabrication of a NiO thin film that is suitable for flexible PSCs. The Ala-complexed NiO is fabricated on the flexible substrate and achieved 17.12% efficiency while retaining 71% of initial PCE after 5,000 bending.

This review provides a comprehensive analysis of the latest advancements in single-crystal perovskite solar cells, emphasizing their superior efficiency and stability. It highlights the critical role of further research in overcoming the limitations of polycrystalline counterparts and advancing commercial viability in photovoltaic technology.

Abstract

The advent of organic–inorganic hybrid metal halide perovskites has revolutionized photovoltaics, with polycrystalline thin films reaching over 26% efficiency and single-crystal perovskite solar cells (IC-PSCs) demonstrating ≈24%. However, research on single-crystal perovskites remains limited, leaving a crucial gap in optimizing solar energy conversion. Unlike polycrystalline films, which suffer from high defect densities and instability, single-crystal perovskites offer minimal defects, extended carrier lifetimes, and longer diffusion lengths, making them ideal for high-performance optoelectronics and essential for understanding perovskite material behavior. This review explores the advancements and potential of IC-PSCs, focusing on their superior efficiency, stability, and role in overcoming the limitations of polycrystalline counterparts. It covers device architecture, material composition, preparation methodologies, and recent breakthroughs, emphasizing the importance of further research to propel IC-PSCs toward commercial viability and future dominance in photovoltaic technology.

In this study, cesium formate (CsFo) is introduced into the CsPbI₃ perovskite precursor solution to induce the crystallization processes at a low energy consumption level and regulate the crystallization process of CsPbI₃ films. Additionally, the pseudo-halide anion, HCOO^–, can be involved in the passivation of iodide vacancies. Consequently, the final photovoltaic performance is enhanced from 18.95% to 21.23%.

Abstract

High-quality CsPbI₃ with low defect density is indispensable for acquiring excellent photoelectric performance. Meticulous regulation of the CsPbI₃ crystal growth processes is both feasible and efficacious in enhancing the quality of perovskite films. In this study, the cesium formate (CsFo) is introduced. On one hand, its low melting point can induce the crystallization processes at a low level of energy consumption. On the other hand, the pseudo-halide anion can participate in the passivation of iodide vacancies, as the formate anion exhibits a relatively higher affinity with iodide vacancies compared to other halides. Consequently, the introduction of CsFo enhances the quality of CsPbI₃ thin films by altering the crystallization process and curbing defect formation. As a result, a steady-state output efficiency of 21.23% and an open-circuit voltage (V_oc ) as high as 1.25 V are achieved, with both parameters ranking among the highest for this type of solar cell.

The excellent wettability reduces the resistance of active layer solution in the spreading process, which effectively suppresses the coffee ring effect during large-area printing, thus obtaining homogeneous green-printed large-area active layer films. Therefore, excellent PCEs of 18.80% and 15.87% are harvested by the interface optimization strategy based on PM6:BTP-eC9 system with the areas of 0.04 and 25 cm², respectively.

Abstract

Large-area organic photovoltaic modules have a wide range of applications in a number of fields due to their unique advantages. Inverted organic solar cells exhibit better air stability and are suitable for all-air printing of large-area modules. However, the mismatch between the surface energy of ZnO and the active layer leads to coffee rings and stick-slip effects during the printing process, resulting in uneven deposition of the active layer. Additionally, the mismatch in energy levels between the active layer and ZnO degrades device performance. Hence, a phenol series of alcohol solutions is utilized to improve the wettability and surface energy of ZnO, enabling the formation of large-area homogeneous active layer films. Hydroxyl groups in the phenol series passivate ZnO surface defects and form hydrogen bonds with small molecules of the acceptor, increasing carrier mobility and improving device performances. Based on the PM6: BTP-eC9 (o-XY) system, the power conversion efficiency (PCE) reaches 18.80% for small-area devices and 15.87% for large-area modules, higher than the forward structure (15.83%). This study offers an effective approach to mitigating large-area active layer film uniformity issues, advancing the preparation of large-area organic photovoltaic modules via all-air printing.

A strategy of “rat glue trap” is proposed to solve the oxidation problem of tin (Sn). A multifunctional additive potassium oxyamine salt, which can effectively trap Sn⁴⁺ impurities and protect Sn²⁺ ions, is introduced to prepare highly efficient tin-lead mixed narrow-bandgap perovskite solar cells and all-perovskite tandem solar cells.

Abstract

Tin-lead (Sn-Pb) mixed perovskite solar cells (PSCs), which serve as bottom subcells in all-perovskite tandem solar cells, are pivotal for developing highly efficient solar cells. However, the vulnerability of stannous (Sn²⁺) to spontaneous oxidation to harmful tetravalent tin (Sn⁴⁺) presents significant challenges. Here, a “mouse glue trap” strategy is proposed to mitigate this issue by introducing a multifunctional additive, oxamidic acid potassium salt (OAPS). This approach effectively traps undesired Sn⁴⁺ impurities through strong interactions between the oxaminic acid groups of OAPS and Sn⁴⁺ impurities. Additionally, OAPS, with its unique functional groups, can inhibit Sn²⁺ oxidation, passivate defects, alleviate stress, and improve crystalline quality in Sn-Pb mixed perovskite films. As a result, the enhanced Sn-Pb mixed narrow-bandgap PSCs incorporating OAPS achieve a power conversion efficiency of 22.04% and exhibit improved storage stability, with 91% retention after 3072 h of storage in an N₂-filled glovebox. Moreover, all-perovskite tandem cells using OAPS-incorporated Sn-Pb narrow-bandgap PSCs as subcells demonstrate efficiencies of 27.17% and 28.31% for two-terminal and four-terminal tandems, respectively, presenting a straightforward approach to optimizing performance in Sn-Pb mixed PSCs and their tandems.

This manuscript improves interfacial contact and optimizes charge transport pathways by constructing a multidimensional dual-carbon electrode structure. At the same time, it employs a single-atom modification strategy to optimize energy level alignment and accelerate carrier transport dynamics, thereby achieving the fabrication of highly efficient and stable carbon-based perovskite solar cells.

Abstract

In the landscape of photovoltaic research, carbon-based perovskite solar cells (C-PSCs) have attracted widespread attention due to their outstanding stability. However, compared to metal-based PSCs, their power conversion efficiency (PCE) lags markedly behind. The key lies in two primary factors: First, the inefficiency of the carbon electrode in transporting and collecting carriers; second, the energy level mismatch with adjacent functional layers. These problems increase both the charge transport resistance and the charge injection barriers, thereby diminishing the overall efficiency of the device. In this study, an effective strategy is presented to tackle this issue by developing modular C-PSCs that utilize dual carbon electrodes and implement multiscale modulation. This approach specifically focuses on three crucial aspects: establishing a highly conductive network, ensuring sufficient interfacial contact, and achieving well-matched energy band alignment. By synergistically incorporating 0D carbon black (CB) and 1D carbon nanotube (CNT) into dual carbon electrodes, a resilient conductive network with enhanced interfacial contact is established, creating favorable conditions for efficient carrier transfer. Additionally, the energy level structure of CB is meticulously adjusted at the molecular scale by introducing individually adsorbed titanium (Ti) atoms, effectively addressing the energy level mismatch with the hole transport layer (spiro-OMeTAD), and notably reducing the charge injection barrier at the interface. Based on the above strategy, the PCE of the C-PSCs has undergone a remarkable enhancement from 15.27% to 22.45%. Moreover, the device shows excellent stability, with its PCE retaining over 95% of the initial value even after 1000 h of continuous operation under one-sun intensity.

A series of organosilanes with different tail functional groups are applied to modify the perovskite. Finally, perovskite solar cells with 3,3,3-trifluoropropyltrimethoxysilane (FPTMS) modification showed a power conversion efficiency (PCE) of 23.0% and the encapsulated device maintained 85% of the initial PCE after 1725 h under continuous 1 sun equivalent illumination in air.

Abstract

Surface or interface engineering is one of the most effective strategies to improve the device performance and stability of perovskite solar cells (PSCs), owing to the fact that the defects are mainly located at the surface. Organosilanes are among the most promising surface modifiers due to their unique cross-linking ability, which makes a robust layer to further protect the underneath perovskites. However, the influence of tail functional groups of organosilanes on the device performance and stability has never been systematically investigated. Herein, a series of organosilanes with different chain lengths, fluorination, and different interactions toward perovskite are applied to modify the perovskite. Tail functional groups that show passivation ability toward perovskite are demonstrated to effectively reduce trap densities and thus improve the power conversion efficiencies (PCEs), while the fluorinated functional groups are beneficial for high stability. Finally, PSCs based on 3,3,3-trifluoropropyltrimethoxysilane (FPTMS) modification showed a high PCE of 23.0% with the best operational stability. The encapsulated device maintained 85% of the initial PCE after 1725 h under continuous 1 sun equivalent illumination in air. The work may provide important insights into designing modifiers for high-performance PSCs with high stability.

The strong coordination interaction between 3AMPY²⁺ and 3D perovskite components as well as the introduced nucleation sites by 3AMPYSnI₄ crystals adjust the phase distribution of 2D and 3D perovskite phase, accompanied by the suppressed Sn²⁺ oxidation and self-p-doping, resulting in lower trap density and non-radiative recombination loss, faster carrier extraction and transfer, and higher stability for 2D-3D Sn-based PSCs.

Abstract

Various popular large organic cations have been extensively used as the essential additives in the perovskite precursor solution due to their satisfactory passivation effect but may produce the low-n value (n ≤ 2) 2D perovskite phases with undesired distribution. Meanwhile, the remaining easy oxidation of Sn²⁺ and the p-type self-doping in the perovskites are also detrimental to the ultimate photovoltaic properties and stability of tin (Sn)-based perovskite solar cells (PSCs). Here, 3AMPYSnI₄ crystals (3AMPY = 3-(aminomethyl)pyridinium)) are designed and applied to adjust the crystallization process and the phase distribution of the Sn-based perovskite. Consequently, the strong coordination interaction between 3AMPY²⁺ and 3D perovskite components and the introduced nucleation sites by 3AMPYSnI₄ crystals not only decreases the low-n value 2D phase and increases 3D perovskite phase, but also inhibits the oxidation of Sn²⁺ and the self-p-doping in the Sn-based perovskites, resulting in lower trap density and non-radiative recombination loss, faster carrier extraction and transfer, and higher stability for 2D-3D Sn-based PSCs. As a result, the optimized devices deliver an increased power conversion efficiency from an initial 10.91% to 13.28% and retain 96.0% of their original performance for more than 3000 h in the nitrogen (N₂) atmosphere.

A perylene-diimide zwitterion PDI-B was designed and synthesized as a universal cathode interlayer material, enabling diverse applications in efficient OSCs. With the assistance of solution-processing, PDI-B tended to form H-aggregate and possessed tight molecular packing in the film, which significantly facilitates the electron transport of OSCs.

Abstract

High-performance organic cathode interlayers (CILs) play a crucial role in the advance of organic solar cells (OSCs). However, organic CILs have exhibited inferior performances to their inorganic counterparts over a long time, due to the inherent shortcoming of poor charge transporting capability. Here, we designed and synthesized a perylene-diimide (PDI) zwitterion PDI-B as high-performance organic CIL for OSCs. We revealed that an obvious H-aggregate of PDI-B was formed during the solution processing, thereby significantly enhancing the charge transporting capability of the CIL. Compared to the classic PDINN, the π–π stacking distance of PDI-B was reduced from 4.2 Å to 3.9 Å, which further facilitated the charge transport. Consequently, PDI-B showed a high conductivity of 1.81×10⁻³S/m; this is comparable to that of inorganic CILs. The binary OSC showed an elevated PCE of 19.23 %, which is among the highest PCE values for binary OSCs. Benefitting from improved solvent resistance and good compatibility with large-area processing method of PDI-B, the photovoltaic performances of inverted and 1-cm² OSC were significantly improved. The results from this work provide a new approach of optimizing the condensed structure of PDI film to boost the charge conductivity, opening an avenue to develop high-performance PDI-based CILs.

The non-fused skeleton strategy has developed novel non-fused star-shaped trimer, which has significantly improved solubility and synthetic yield, and effectively inhibited excessive molecular aggregation. The resulting based on 3BTT6F exhibit superior photovoltaic performance. Importantly, the non-fused 3D skeleton is conducive to improving intermolecular interactions, thereby contributing to the exceptional stability of the binary devices.

Abstract

Organic solar cells (OSCs) based on giant molecular acceptors (GMAs) have attracted extensive attention due to their excellent power conversion efficiency (PCE) and operation stability. However, the large conjugated plane of GMAs poses great challenges in regulating the solubility, over-size aggregation and yield, which in turn further constrains their development in commercial products. Herein, we employ a non-fused skeleton strategy to develop novel non-fused star-shape trimers (3BTT6F and 3BTT6Cl) for improving device performance. Single-bond linkage can break the rigid planarity to form a 3D architecture, generating multidimensional charge transfer pathways. Importantly, the non-fused skeleton strategy can not only significantly improve solubility and synthesis yield, but also effectively suppress molecular excessive aggregation. Consequently, due to the optimized film-forming process and charge dynamics, 3BTT6F-based binary device obtains a high PCE of 17.52 %, which is significantly higher than the reported fully fused trimers. Excitingly, 3BTT6F-based ternary device even obtains a top-level PCE of 19.26 %. Furthermore, the non-fused star-shape configuration also endows these acceptors with enhanced intermolecular interaction in the active layer, demonstrating excellent operational stability. Our work emphasizes the potential of non-fused star-shape trimers, providing a new pathway for achieving highly efficient and stable OSCs.

A promising method to tune the Work Function (W_F ) of carbon electrode directly by Mn₃O₄ as a novel binder achieves high-performance hole transport layer (HTL)-free carbon-based peovskite solar cells (C-PSCs). The carbon electrode can be easily prepared by a low-temperature solution-processed way. A champion power conversion efficiency (PCE) of C-PSCs without HTL >19% is obtained.

Abstract

Perovskite solar cell (PSC) is a promising photovoltaic technology that achieves over 26% power conversion efficiency (PCE). However, the high materials costs, complicated fabrication process, as well as poor long-term stability, are stumbling blocks for the commercialization of the PSCs in normal structures. The hole transport layer (HTL)-free carbon-based PSCs (C-PSCs) are expected to overcome these challenges. However, C-PSCs have suffered from relatively low PCE due to severe energy loss at the perovskite/carbon interface. Herein, the study proposes to boost the hole extraction capability of carbon electrode by incorporating functional manganese (II III) oxide (Mn₃O₄). It is found that the work function (W _F) of the carbon electrode can be finely tuned with different amounts of Mn₃O₄ addition, thus the interfacial charge transfer efficiency can be maximized. Besides, the mechanical properties of carbon electrode can also be strengthened. Finally, a PCE of 19.03% is achieved. Moreover, the device retains 90% of its initial PCE after 2000 h of storage. This study offers a feasible strategy for fabricating efficient paintable HTL-free C-PSCs.