Publication date: 1 December 2024
Source: Nano Energy, Volume 131, Part A
Author(s): Qiaojiao Zou, Cao Yu, Yu Zhao, Ying Liu, Gangqiang Dong, Qi Wang, Xiaochao Ran, Yongsheng Zhang, Xinmin Cao, Jian Zhou, Xinbo Yang, Xiaohong Zhang, Ying Zhao, Xiaodan Zhang
A stable ferrocenium hexafluorophosphate (FcPF6) engineered spiro-OMeTAD is developed to suppress Li+ migration and passivate the surface defects of perovskite. The additive of FcPF6 facilitates the rapid generation of spiro-OMeTAD+ radicals, promoting efficient charge transfer. The efficiencies reach 22.13% in 6 × 6 cm2 and 20.27% in 10 × 10 cm2 modules.
Li-TFSI doped spiro-OMeTAD is widely recognized as a beneficial hole transport layer (HTL) in perovskite solar cells (PSCs), contributing to high device efficiencies. However, the uncontrolled migration of lithium ions (Li+) during device operation has impeded its broad adoption in scalable and stable photovoltaic modules. Herein, an additive strategy is proposed by employing ferrocenium hexafluorophosphate (FcPF6) as a relay medium to enhance the hole extraction capability of the spiro-OMeTAD via the instant oxidation function. Besides, the novel Fc–Li interaction effectively restricts the movement of Li+. Simultaneously, the dissociative hexafluorophosphate group is cleverly exploited to regulate the unstable iodide species on the perovskite surface, further inhibiting the formation of migration channels and stabilizing the interfaces. This modification leads to power conversion efficiencies (PCEs) reaching 22.13% and 20.27% in 36 cm2 (active area of 18 cm2) and 100 cm2 (active area of 56 cm2) perovskite solar modules (PSMs), respectively, with exceptional operational stability obtained for over 1000 h under the ISOS-L-1 procedure. The novel FcPF6-based engineering approach is pivotal for advancing the industrialization of PSCs, particularly those relying on high-performance spiro-OMeTAD- based HTLs.
Publication date: 1 December 2024
Source: Nano Energy, Volume 131, Part A
Author(s): EQ Han, Jung-Ho Yun, Inhee Maeng, Tengfei Qiu, Yurou Zhang, Eunyoung Choi, Su-Min Lee, Peng Chen, Mengmeng Hao, Yang Yang, Hongxia Wang, Bo Wei Zhang, Jae Sung Yun, Jan Seidel, Miaoqiang Lyu, Lianzhou Wang
Publication date: 1 December 2024
Source: Nano Energy, Volume 131, Part A
Author(s): Zhiyuan Dai, Yang Yang, Xiaofeng Huang, Shuyuan Wan, Li Yuan, Hang Wei, Siqing Nie, Zhe Liu, Yongzhen Wu, Ruihao Chen, Hongqiang Wang
Interface optimization is of significant value in perovskite solar cells. Multifunctional passivators can passivate the surface, suppress defects, and induce stability. Cyanoguanidine iodide outperforms other typical passivators, boosting performance from 20.44% to 23.04%, with an upgraded open-circuit voltage to 1119 mV.
The nonradiative recombination arising from the interfaces of perovskite solar cells (PSCs) pose a hurdle, impacting both the efficiency and stability of devices. Functionalized organic molecules can passivate the perovskite surface to suppress the defects and can also fine-tune the microstructure. This in turn promotes reliability and performance enhancement in solar cells. Using a design protocol, cyanoguanidine diiodide is synthesized and employed as a surface passivator for the fabrication of PSCs, and boosted performance from 20.44% to 23.04% is achieved. This improvement stems from an improved fill factor reaching up to 80.64%, together with the open-circuit voltage (V oc) measuring 1119 mV. The steady-state photoluminescence and microstructure of passivated perovskites display significant surface modification of the perovskite film which favorably impacts the charge carrier transfer at the interface of perovskite and Spiro-OMeTAD. Our findings suggest that improved solar cell performance is due to the synergetic effect of amino and cyano functional groups along with the iodide reservoir in the organic passivator.
Heat-assisted intensive light-soaking of silicon heterojunction solar cells establishes at least two distinct mechanisms. One mechanism is the passivation improvement between c–Si wafer and hydrogenated amorphous silicon interface, which improves the open-circuit voltage and fill factor (FF). The second mechanism is the enhancement of active doping density in the doped layers, which contributes to the FF enhancement.
Heat-assisted intensive light soaking has been proposed as an effective posttreatment to further enhance the performance of silicon heterojunction (SHJ) solar cells. In the current study, it is aimed to distinguish the effects of heat and illumination on different (doped and undoped) layers of the SHJ contact stack. It is discovered that both elevated temperature and illumination are necessary to significantly reduce interface recombination when working effectively together. The synergistic effect on passivation displays a thermal activation energy of approximately 0.5 eV. This is likely due to the photogenerated electron/hole pairs in the c–Si wafer, where nearly all of the incident light is absorbed. By distinguishing between the effects of light and heat effects on the conductivity of p- and n-type doped hydrogenated amorphous silicon (a–Si:H) layers, it is demonstrated that only heat is accountable for the observed rise in conductivity. According to numerical device simulations, the significant contribution to the open-circuit voltage enhancement arises from the reduced density of defect states at the c–Si/intrinsic a–Si:H interface. In addition, the evolution of the fill factor is highly dependent on changes in interface defect density and the band tail state density of p-type a–Si:H.
A new additive FIPh-A is synthesized to improve the stability of perovskite films. DFT calculations and experimental results demonstrate that FIPh-A molecules, containing carbonyl, amino, and iodotetrafluorophenyl groups, effectively stabilize the PbI6 framework, suppress I⁻ ion migration, and reduce defects within the perovskite films. Incorporating FIPh-A into PSCs led to a champion efficiency of 24.60% with superior long-term stability.
Perovskite solar cells (PSCs), while highly efficient, face stability challenges that hinder their commercial application. These instability issues mainly arise from the fragile nature of Pb─I bonds in perovskites, which easily break under environmental stresses such as heat and light, leading to the breakdown of the [PbI6] framework and irreversible degradation. To address these issues, a multifunctional molecule, N1,N4-bis(2,3,5,6-tetrafluoro-4-iodophenyl)terephthalamide (FIPh-A), is designed and synthesized to enhance the stability of perovskite films and devices. FIPh-A molecule possesses carbonyl, amino, and iodotetrafluorophenyl groups that bind and stabilize Pb2+ ions and [PbI6]4− octahedra structure, preventing ion migration in perovskite films. The activation energy of ion migration increases obviously from 0.28 eV to 0.39 eV by adding FIPh-A verified by experiment results. The residual strain is also released efficiently by introducing FIPh-A molecule into perovskite films characterized by grazing incidence X-ray diffraction. The champion PSC with FIPh-A achieves a power conversion efficiency of 24.60%. After 500 h of continuous illumination (ISOS-L-1) and 300 h of thermal aging at 80 °C (ISOS-D-2I), these PSCs with FIPh-A maintained 93% and 77% of their initial efficiency, respectively. These results emphasize the potential of multifunctional additives in overcoming the stability challenges of PSCs, thereby facilitating their commercial advancement.
The inadequate crystallization of the two-step method has always puzzled researchers in perovskite solar cells. Two kinds of metal-organic frameworks to increase interface contact and reduce the nucleation crystallization barrier, resulting in a high-quality film are introduced. The modified perovskite solar cells exhibited a champion efficiency of 24.17% with good humidity and thermal stability.
The two-step sequential deposition method is considered a potential way for the large-scale manufacture of perovskite solar cells (PSCs) with high power conversion efficiency and reproducibility. However, the dense lead iodide (PbI2) film interferes with its full contact with organic solutions, resulting in an inadequate reaction at the interface. Herein, 2 kinds of metal-organic framework (MOF) are introduced, amorphous Ni-MOF-74 (amNi-MOF-74) and crystalline Zn-MOF-74 (crZn-MOF-74), into PbI2 for regulating crystallization. Compared to crZn-MOF-74, the incorporation of amNi-MOF-74 exhibited rapid nucleation, resulting in high-quality perovskite films with large grain size, low trap density, and enhanced charge transfer between the perovskite and charge transfer layers. Meanwhile, the content of unstable phase PbI2 left in perovskite films due to insufficient reaction is also reduced. The amNi-MOF-74 modified PSCs exhibited a champion power conversion efficiency of 24.17% with good humidity and thermal stability. The unencapsulated device maintains 90% of its initial efficiency after 1000 h storage in dark ambient conditions with ≈30% relative humidity. This strategy provides an effective approach for promoting the crystallization process of perovskite and fabricating efficient and stable PSCs.
A bidirectionally electric dipole field at grain boundary is fabricated by columnar macrocyclic cucurbituril molecule that serves as a host to induce supramolecular passivation, which significantly improves the efficiency and stability of an all-inorganic CsPbI2Br PSC.
Solidifying the soft lattice of all-inorganic mixed-halide perovskites is of great importance to restrain the notorious halide segregation under persistent light illumination. Herein, a multifunctional columnar macrocyclic molecule additive, namely cucurbituril into perovskite precursor to enhance the crystallization and reduce the defect density in the final perovskite film is introduced. Based on the theoretical calculation and simulation, the cucurbituril molecule with a strong double-ended negatively-charged cavity surrounded by terminated oxygen atoms not only coordinates with dangling Pb2+ ions to form host-guest complexation but also induces an electric dipole field at perovskite grain boundary to effectively repel the iodide ion migration from the inside grain to the defective boundary, significantly suppressing the halide segregation and improving the device performance. As a result, the carbon-based, all-inorganic CsPbI2Br solar cell achieves an enhanced efficiency of 15.59% with great tolerance to environmental stresses. These findings provide new insights into the development of a novel passivation strategy with macrocyclic molecules for making high-efficiency and stable perovskite solar cells.
1D porous channels and high crystalline orientation of imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) facilitate the crystallization and defect elimination of the perovskite film. The recombination of photogenerated carriers is thus reduced and the perovskite solar cells exhibit excellent efficiency and high stability.
The low crystallinity of the perovskite layers and many defects at grain boundaries within the bulk phase and at interfaces are considered huge barriers to the attainment of high performance and stability in perovskite solar cells (PSCs). Herein, a robust photoelectric imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) is introduced to precisely control the perovskite crystallization process and effectively passivate defects at grain boundaries through a sequential deposition method. The 1D porous channels, abundant active sites, and high crystallization orientation of PyPor-COF offer advantages for regulating the crystallization of PbI2 and eliminating defects. Moreover, the intrinsic electronic characteristics of PyPor-COF endow a more closely matched energy level arrangement within the perovskite layer, which promotes charge transport and thereby suppresses the recombination of photogenerated carriers. The champion PSCs containing PyPor-COF achieved power conversion efficiencies of 24.10% (0.09 cm2) and 20.81% (1.0 cm2), respectively. The unpackaged optimized device is able to maintain its initial efficiency of 80.39% even after being exposed to air for 2000 h. The device also exhibits excellent heating stability and light stability. This work gives a new impetus to the development of highly efficient and stable PSCs via employing COFs.
Nature Communications, Published online: 04 September 2024; doi:10.1038/s41467-024-52198-5
The lead halide octahedron framework is mainly stabilized via optimization of bonding characteristics and dimensionality. Here, the authors employ bidentate ligands to in-situ form lead iodide chelates layer for surface passivation, achieving device efficiency over 25% in perovskite solar cells.Publication date: October 2024
Source: Applied Materials Today, Volume 40
Author(s): Edwin T. Mombeshora, Edigar Muchuweni, Alexander J. Doolin, Matthew L. Davies, Bice S. Martincigh, Vincent O. Nyamori
This work reveals a structure-property relationship where the structural entropy of fusion (ΔS fus) drives the melting of A2PbX4 layered perovskites. Non-covalent interactions and steric hindrances rigidify the A-site organic layer in solid state, and their removal in molten state yields high ΔS fus and low melting temperature. The stable melt enables solvent- and vacuum-free melt-pressed films for optoelectronic devices.
Typical layered 2D A2PbX4 (A: organic ammonium cation, X: Br, I) perovskites undergo irreversible decomposition at high temperatures. Can they be designed to melt at lower temperatures without decomposition? Which thermodynamic parameter drive the melting of layered perovskites? These questions are addressed by considering the melt of A2PbX4 as a mixture of ions (like ionic liquids), and hypothesized that the increase in the structural entropy of fusion (ΔS fus) will be the driving force to decrease their melting temperature. Then to increase structural ΔSfus, A-site cations are designed that are rigid in the solid crystal, and become flexible in the molten state. Different tail groups in the A-site cations form hydrogen-, halogen- and even covalent bonding-interactions, making the cation-layer rigid in the solid form. Additionally, the rotation of ─NH3 + head group is suppressed by replacing ─H with ─CH3, further enhancing the rigidity. Six A2PbX4 crystals with high ΔS fus and low melting temperatures are prepared using this approach. For example, [I−(CH2)3−NH2(CH3)]2PbI4 reversibly melts at 388 K (decomposition temperature 500 K), and then recrystallizes back upon cooling. Consequently, melt-pressed films are grown demonstrating the solvent- and vacuum-free perovskite films for future optoelectronic devices.
MIX-D18, by mixing HW-D18 (high molecular weight D18) and LW-D18 (low molecular weight D18), can form multiscale fibrous morphology. The finer nanofibers of HW-D18 can increase Donor/Acceptor contact, enhancing exciton dissociation and collection efficiency, while the thicker nanofibers of LW-D18 can improve crystallinity and boost charge transport capability. Ultimately, a efficiency of 20.0% is achieved by MIX-D18:L8-BO device.
This study underscores the significance of precisely manipulating the morphology of the active layer in organic solar cells (OSCs). By blending polymer donors of D18 with varying molecular weights, a multiscale interpenetrating fiber network structure within the active layer is successfully created. The introduction of 10% low molecular weight D18 (LW-D18) into high molecular weight D18 (HW-D18) produces MIX-D18, which exhibits an extended exciton diffusion distance and orderly molecular stacking. Devices utilizing MIX-D18 demonstrate superior electron and hole transport, improves exciton dissociation, enhances charge collection efficiency, and reduces trap-assisted recombination compared to the other two materials. Through the use of the nonfullerene acceptor L8-BO, a remarkable power conversion efficiency (PCE) of 20.0% is achieved. This methodology, which integrates the favorable attributes of high and low molecular weight polymers, opens a new avenue for enhancing the performance of OSCs.
Here, we synthesized a discotic liquid crystal molecule (HAT5) and combined it with o-F-PEAI to construct an interface passivation layer. The introduction of HAT5 promotes the transport of holes in PSCs, changing the edge-on orientation of o-F-PEAI to a more favorable face-on orientation for charge transfer, inhibiting the migration of o-F-PEAI to the bottom of perovskite, and increasing the activation energy of ion migration. In the end, we achieved a championship efficiency of 25.02 %. Unpacked PSCs, whether heated at 85 °C or aged under continuous sunlight for 1008 hours, can maintain an initial efficiency of over 80 %.
Traditionally used phenylethylamine iodide (PEAI) and its derivatives, such as ortho-fluorine o-F-PEAI, in interfacial modification, are beneficial for perovskite solar cell (PSC) efficiency but vulnerable to heat stability above 85 °C due to ion migration. To address this issue, we propose a composite interface modification layer incorporating the discotic liquid crystal 2,3,6,7,10,11-hexa(pentoxy)triphenylene (HAT5) into o-F-PEAI. The triphenyl core in HAT5 promotes π–π stacking self-assembly and enhances its interaction with o-F-PEAI, forming an oriented columnar phase that improves hole extraction along the one-dimensional direction. HAT5 repairs structural defects in the interfacial layer and retains the layered structure to inhibit ion migration under heating. Ultimately, our approach increases the efficiency of solar cells from 23.36 % to 25.02 %. The thermal stability of the devices retains 80.1 % of their initial efficiency after aging at 85 °C for 1008 hours without encapsulation. Moreover, the optimized PSCs maintained 82.4 % of the initial efficiency after aging under one sunlight exposure for 1008 hours. This work provides a simple yet effective strategy using composite materials for interface modification to enhance the thermal and light stability of semiconductor devices.
Publication date: 20 November 2024
Source: Joule, Volume 8, Issue 11
Author(s): Mingquan Tao, Yang Wang, Kun Zhang, Zhaofei Song, Yangjie Lan, Haodan Guo, Lutong Guo, Xiwen Zhang, Junfeng Wei, Dongqiang Cao, Yanlin Song
Nature Communications, Published online: 01 September 2024; doi:10.1038/s41467-024-51760-5
Self-assembled monolayers are essential for achieving high performance solar cells by minimizing interfacial energy losses. Here, authors the develop a co-adsorb strategy with a small molecule to provide a favorable heterointerface, realizing high efficiency in p-i-n perovskite and organic devices.
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
An efficient strategy using Na2SiO3 surface modification to efficiently passivate the defects at the TiO2/CsPbIBr2 interface is demonstrated. After Na2SiO3 surface treatment, the non-radiative recombination is reduced, thereby enhancing the electron extraction efficiency. Consequently, the carbon-based all-inorganic CsPbIBr2 perovskite solar cells treated with Na2SiO3 yield a PCE of 10.85% with less hysteresis and improved stability.
CsPbIBr2 has garnered significant interest due to its ideal bandgap and good stability. However, defects formed at the interface between the electron transport layer and the perovskite can lead to increased non-radiative recombination, which negatively impacts both the power conversion efficiency (PCE) of perovskite solar cells and the long-term stability of the cells. Herein, the TiO2/perovskite interface is modified by adding sodium silicate to passivate the defects on the interface. The introduction of Na+ partially reduces Ti4+ to Ti3+ in TiO2, thereby passivating trap states caused by oxygen vacancy defects and adjusting the energy level alignment between TiO2 and the perovskite film, enhancing the carrier transport efficiency. Additionally, SiO3 2− can form SiOPb (and Cs) bonds with the undercoordinated Pb2+ and Cs+ on the surface of the perovskite layer, effectively passivating surface defects of the perovskite film and thereby improving the efficiency of the devices. Ultimately, the carbon-based all-inorganic CsPbIBr2 perovskite solar cells treated with Na2SiO3 exhibit a significantly improved PCE of 10.85% compared to 8.62% of the control sample and achieve a high open-circuit voltage of 1.31 V. With this modification, the devices also demonstrate reduced hysteresis effects and enhanced stability.
Transparent electrodes are crucial in optoelectronic devices. This study presents a two-in-one electron transport layer and transparent electrodes using polyethylenimine ethoxylated (PEIE)-modified poly(benzodifurandione) (PBFDO) films, offering low resistance, low work function, and high transparency. These layers achieve performance comparable to ITO electrodes, enabling all-organic solar cells with >15.1% efficiency under indoor lighting, promising for fully printed devices.
Transparent electrodes (TEs) are vital in optoelectronic devices, enabling the interaction of light and charges. While indium tin oxide (ITO) has traditionally served as a benchmark TE, its high cost prompts the exploration of alternatives to optimize electrode characteristics and improve device efficiencies. Conducting polymers, which combine polymer advantages with metal-like conductivity, emerge as a promising solution for TEs. This work introduces a two-in-one electron transport layer (ETL) and TE based on films of polyethylenimine ethoxylated (PEIE)-modified poly(benzodifurandione) (PBFDO). These PEIE-modified PBFDO layers exhibit a unique combination of properties, including low sheet resistance (130 Ω sq−1), low work function (4.2 eV), and high optical transparency (>85% in the UV–vis-NIR range). In contrast to commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the doping level of PBFDO remains unaffected by the PEIE treatment, as verified through UV–vis-NIR absorption and X-ray photoelectron spectroscopy measurements. When employed as a two-in-one ETL/TE in organic solar cells, the PEIE-modified PBFDO electrode exhibits performance comparable to conventional ITO electrodes. Moreover, this work demonstrates all-organic solar cells with record-high power conversion efficiencies of >15.1% under indoor lighting conditions. These findings hold promise for the development of fully printed, all-organic optoelectronic devices.
P-xylylenediphosphonic acid (p-XPA) was introduced between the hole transport layer (HTL) and the perovskite film. P-XPA made the HTL planar, promoted perovskite crystallization, and effectively passivated the bottom defects of the perovskite film. Ultimately, the device power conversion efficiency reached 25.87 % and the stability was significantly improved.
[4-(3,6-dimethyl-9H-carbazol-9yl)butyl]phosphonic acid (Me-4PACz) self-assembly material has been recognized as a highly effective approach for mitigating nickel oxide (NiOx) surface-related challenges in inverted perovskite solar cells (IPSCs). However, its uneven film generation and failure to effectively passivate the buried interface defects limit the device‘s performance improvement potential. Herein, p-xylylenediphosphonic acid (p-XPA) containing bilateral phosphate groups (−PO3H2) is introduced as an interface layer between the NiOx/Me-4PACz and the perovskite layer. P-XPA can flatten the surface of hole transport layer and optimize interface contact. Meanwhile, p-XPA achieves better energy level alignment and promotes interfacial hole transport. In addition, the bilateral −PO3H2 of p-XPA can chelate with Pb2+ and form hydrogen bond with FA+ (formamidinium cation), thereby suppressing buried interface non-radiative recombination loss. Consequently, the IPSC with p-XPA buried interface modification achieves champion power conversion efficiency of 25.87 % (certified at 25.45 %) at laboratory scale (0.0448 cm2). The encapsulated target device exhibits better operational stability. Even after 1100 hours of maximum power point tracking at 50 °C, its efficiency remains at an impressive 82.7 % of the initial efficiency. Molecules featuring bilateral passivation groups optimize interfacial contact and inhibit interfacial recombination, providing an effective approach to enhancing the stability and efficiency of devices.
The SA1 additive with a planar structure can enhance molecular order and packing of active layer. In this way, the phonon scattering is suppressed in the SA1-assisted blend film, leading to a remarkable PCE of 20 % for the ternary device.
Strong electron-phonon coupling can hinder exciton transport and induce undesirable non-radiative recombination, resulting in a shortened exciton diffusion distance and constrained exciton dissociation in organic solar cells (OSCs). Therefore, suppressing electron-phonon coupling is crucially important for achieveing high-performance OSCs. Here, we employ the solid additive to regulating electron-phonon coupling in OSCs. The planar configuration of SA1 confers a significant advantage in suppressing lattice vibrations in the active layers, reducing the scattering of excitons by phonons. Consequently, a slow but sustained hole transfer process is identified in the SA1-assisted film, indicating an enhancement in hole transfer efficiency. Prolonged exciton diffusion length and exciton lifetime are achieved in the blend film processed with SA1, attributed to a low non-radiative recombination rate and low energetic disorder for charge carrier transport. As a result, a high efficiency of 20 % was achieved for ternary device with a remarkable short-circuit current. This work highlights the important role of suppressing electron-phonon coupling in improving the photovoltaic performance of OSCs.
