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iEnergy: Over 25% Record-High Efficiency! Flexible Perovskite Solar Cells
2024
04-09
Yujing Bi’s Nature Electronics: Over 16% Record Efficiency! Quasi-Two-Dimensional Perovskite Blue Light-Emitting Diode
2023
05-04
Yan He and Chen Shangshang in Nature Communications: Fullerene-Host Polymers Enhance the Mechanical Stability of Photovoltaic Devices, Achieving Over 18% Efficiency in All-Polymer Solar Cells
04-26
Sun Yat-sen University Reports in Nature Communications: Silicon-Based Catalyst with Isolated Cobalt Atoms Enables Highly Efficient Photocatalytic CO₂ Reduction
Currently, many reported heterogeneous single-atom photocatalysts are limited by low photon utilization and low metal loading. Crystalline silicon, with its ideal bandgap and strong light-absorption capability, is an excellent substrate material for single-atom photocatalysts. However, because crystalline silicon is an atomic crystal characterized by high structural rigidity and high formation energy, effective synthetic methods for preparing silicon-based single-atom catalysts remain lacking. This work presents a solid-phase epitaxial growth approach to synthesize a class of silicon-based catalysts with a relatively high single-atom cobalt loading (3.4 wt%), which, in model experiments on photocatalytic CO2 reduction to syngas, achieves high atom utilization, high total catalytic turnover number, and high quantum yield.
04-06
NREL’s Joseph M. Luther, Zhu Zonglong of City University of Hong Kong, and others: Co-deposition of hole-selective contact layers and perovskite layers enhances the processability of perovskite solar cells.
03-20
HZB Breaks Another Record: Perovskite–Silicon Tandem Solar Cell with Certified Efficiency of 32.5%
Scientists at the Helmholtz-Zentrum Berlin (HZB) in Germany claim to have fabricated a perovskite–silicon tandem solar cell with an efficiency of 32.5%, setting a new world-record efficiency.
2022
12-21
This new type of photovoltaic device deserves attention.
1. Organic Solar Cells with 19.10% Efficiency and 80.5% Fill Factor Morphology plays a crucial role in charge generation and collection, thereby influencing the device performance of organic solar cells (OSCs). However, the pool of additives available for optimizing OSC morphology is limited, particularly for emerging layer-by-layer (LbL) OSCs, which has hindered further improvements in photovoltaic performance. Researchers led by Peng Qiang and Xiaopeng Xu at Sichuan University have reported a novel approach that employs conjugated polymers as additives to optimize the active-layer morphology, thereby enhancing the photovoltaic performance of LbL-OSCs. Four polymers—P-H, P-S, P-F, and P-Cl—with distinct side chains were synthesized. Due to unfavorable energy-level alignment and detrimental molecular interactions, these polymers exhibit poor performance as donor materials or additives in bulk-heterojunction (BHJ) devices. In contrast, they prove to be effective additives for optimizing the PM6 fiber matrix, promoting the infiltration of BTP-eC9 and facilitating the formation of an interwoven D/A dual-continuous network with well-defined vertical phase separation. Further optimization of this morphology through side-chain engineering progressively improves charge separation and collection. The results demonstrate that incorporating a small amount of P-Cl as an additive into the PM6 layer leads to an optimized morphology, resulting in a champion power conversion efficiency (PCE) of 19.10% and a fill factor (FF) of 80.5%. https://onlinelibrary.wiley.com/doi/10.1002/adma.202208279 2. 19% Efficiency! Non-Fullerene Acceptor Heterojunction Organic Solar Cells The structural order and aggregation of non-fullerene acceptors (NFAs) are critical for their light absorption, phase separation, and charge transport properties when blended with electron-donor photovoltaic materials, ultimately determining the power conversion efficiency (PCE) of the corresponding organic solar cells (OSCs). Researchers led by Wang Tao at Wuhan University of Technology have demonstrated that the fibrillation of the small-molecule NFA L8-BO, facilitated by the molten-ring solvent additive 1-fluoronaphthalenesulfonic acid (FN), significantly enhances device PCE. Molecular dynamics simulations reveal that FN adsorbs onto the main chain of L8-BO, strengthening intermolecular packing along the conjugated backbone and inducing one-dimensional self-assembly of L8-BO into fine fibers with a compact polycrystalline structure. When incorporated into a pseudo-bulk heterojunction (P-BHJ) active layer using D18 as the donor, the L8-BO fibers exhibit enhanced light absorption, charge transport, and collection properties, boosting the PCE of the D18/L8-BO binary P-BHJ blend from 16.0% to an unprecedented 19.0%, accompanied by a high fill factor of 80%. This work showcases a strategy for leveraging fibrillating NFAs to enhance OSC performance. https://onlinelibrary.wiley.com/doi/10.1002/adma.202208211 3. Regulating Charge-Carrier Recombination in the Interconnect Layer to Enhance Efficiency and Stability of Monolithic Perovskite/Organic Tandem Cells In single-junction solar cells, charge carriers can be efficiently extracted and collected via the electrodes, leading to minimal charge-carrier accumulation and low energy loss (Eloss). However, in tandem solar cells (TSCs), achieving a balance between the densities of holes and electrons extracted from the two sub-cells to promote efficient recombination in the interconnect layer (ICL) poses a significant challenge. Researchers led by Li Yaowen at Soochow University have proposed a charge-carrier–dynamic management strategy for inorganic perovskite/organic TSCs. This strategy focuses on simultaneously tuning the defect states in the CsPbI1.9Br1.1 perovskite within the front sub-cell and the hole-transport capability from the perovskite to the ICL. As a result, the target hole density on the perovskite surface and the pre-ICL hole losses are markedly increased. Consequently, the hole/electron density imbalance in the ICL is effectively reduced, leading to balanced charge-carrier recombination and lower Eloss in the TSC. The resulting inorganic perovskite/organic TSC with a 0.062-cm² active area exhibits a remarkable power conversion efficiency (PCE) of 23.17%, with an ultra-high open-circuit voltage (Voc) of 2.15 V, while the 1.004-cm² device demonstrates a PCE of 21.69%, showing weak size dependence. Moreover, this charge-carrier dynamic management strategy also effectively enhances the UV stability of TSCs. https://doi.org/10.1002/adma.202208604 4. 19.12% Efficiency! Solar Cells Based on Multifunctional, Low-Cost Polymers Derived from 4-Chlorothiazole Thanks to the emergence of narrow-bandgap small-molecule acceptors (SMAs), particularly those in the “Y” series, the power conversion efficiency (PCE) of polymer solar cells (PSCs) has improved rapidly. However, aside from PM6 and D18, high-efficiency, easily synthesized, and broadly applicable polymer donors remain relatively scarce. Researchers led by Min Jie at Wuhan University have designed and synthesized two structurally simple polymer donors based on 4-chlorothiazole derivatives: PTz3Cl and PBTTz3Cl. Compared with PTz3Cl, PBTTz3Cl exhibits slightly weaker intermolecular forces; when blended with the SMA L8-BO, it achieves a PCE of 18.38%, owing to the stronger donor–acceptor interactions between PBTTz3Cl and L8-BO, which facilitate an optimal phase-separation morphology. Further studies reveal that PBTTz3Cl delivers excellent photovoltaic performance across a wide range of SMA materials, underscoring its versatility. Building on this, a ternary PSC was designed, incorporating BTP-eC9 as a guest molecule into the PBTTz3Cl:L8-BO host system. Due to the further optimized blending morphology and more balanced charge transport, the PCE rises to 19.12%, one of the highest values ever reported for PSCs. This work offers a new design for low-cost electron-deficient units, paving the way for highly versatile, high-performance polymer donors. https://onlinelibrary.wiley.com/doi/10.1002/adma.202208750 5. 18.14% Record Efficiency! Ternary All-Polymer Solar Cells Fabricated via Two-Step Sequential Deposition Achieving finely tuned active-layer morphologies with appropriate vertical phase separation to promote charge generation and transport has long been a primary goal in the pursuit of high-efficiency bulk-heterojunction (BHJ) all-polymer solar cells (all-PSCs). Researchers led by Min Jie at Wuhan University have proposed a solution that synergistically combines a ternary blending strategy with a layer-by-layer (LBL) deposition process. By introducing a crystallinity-enhancing synthetic polymer acceptor, PY-Cl, into the designed host receptor PY-SSe-V, the vertical phase distribution and molecular ordering in LBL-type ternary all-PSCs can be improved, outperforming the LBL-type PM6/PY-SSe-V binary all-PSCs. The formation of an excellent microstructure not only facilitates charge transport and extraction but also reduces energy disorder and non-radiative recombination losses, thereby simultaneously enhancing all three photovoltaic parameters. Consequently, the PM6/(PY-SSe-V:PY-Cl) ternary all-PSC achieves a peak efficiency of 18.14%, one of the highest values reported for all-PSCs to date. This work provides a simple yet effective LBL-based ternary strategy for realizing high-efficiency all-PSCs. https://onlinelibrary.wiley.com/doi/10.1002/adma.202209350
12-02
Two photovoltaic AM papers published in a single day—this team is worth watching!
Researcher Min Jie has long been engaged in the design and synthesis of organic optoelectronic functional materials, studies on morphology, physics, and device stability, research and development of device architectures and fabrication processes, and the industrialization of flexible batteries, with a particular focus on advancing third-generation flexible organic solar cell technology. As of May 2020, he had published more than 60 academic papers as first or corresponding author, including in journals such as Joule, Nature Communications, Energy & Environmental Science, Advanced Materials, and Angewandte Chemie. His publications have been cited over 5,000 times in Google Scholar, with an H-index of 37.
11-25
Submitted to Advanced Materials: Molecular Crystallinity and Twin Carrier Transport in Non-Fullerene Organic Photovoltaic Cells by Liu Feng, Gao Ke of Shandong University, and Others
Professor Feng Liu and Professor Yongming Zhang of Shanghai Jiao Tong University, Professor Ke Gao of Shandong University, and Professor Alex Jen of City University of Hong Kong have collaborated on a detailed study of the structural details and arrangement patterns of classic ITIC-type non-fullerene acceptor molecules across the “single crystal–pure film–blended film” hierarchy. Their work reveals a strong spontaneous carrier-generation phenomenon in non-fullerene acceptors (NFAs) and identifies two primary pathways for charge generation in organic thin-film photovoltaic cells: (1) intrinsic carrier generation within the NFA phase, and (2) exciton dissociation at the donor–acceptor interface to produce free carriers. This dual-channel mechanism represents another significant advantage of NFAs beyond their superior light absorption and favorable energy-level alignment, collectively underpinning the success of NFA materials in organic photovoltaics. Figure 1. (a) Morphology and (b) photophysical pathway diagram of blended films in non-fullerene organic solar cells. The paper begins with a comparative analysis of the crystal structures of three NFA molecules: ITIC, 4TIC, and 6TIC. It finds that π–π stacking interactions and side-chain interactions are the two dominant factors governing the crystal structure of NFAs. The volume ratio of the side chains to the molecular backbone is a key determinant of spatial confinement. For ITIC, this ratio is 1.059, resulting in a two-dimensional brickwork packing where the backbone forms layered structures through terminal π–π interactions, while the side chains aggregate in the interlayer voids. As the backbone length decreases, the side-chain-to-backbone volume ratio for 4TIC increases to 1.146, leading the molecule to adopt a three-dimensional web-like structure. In 4TIC, the side chains assemble in a tightly packed configuration, filling the spaces around the backbone’s π–π stacks to achieve a densely packed arrangement balanced by multiple intermolecular forces. When the backbone is further elongated, the side-chain-to-backbone volume ratio for 6TIC drops to 1.030, prompting the molecule to form a hierarchical structure. Under the influence of both side-chain interactions and π–π stacking, 6TIC first self-assembles into a zigzag pattern; these units then link via hydrogen bonds to form two-dimensional assembly layers, which in turn stack in a three-dimensional architecture through intercalation of blue- and yellow-colored conformational molecules. Figure 2. Crystal structures of the three molecules. Next, the authors employ grazing-incidence wide-angle X-ray scattering (GIWAXS) to analyze the crystalline structures of NFA molecules in both pure and blended films. By comparing pure films prepared under different processing conditions—specifically, with or without the DIO additive—and combining GIWAXS experiments with computational simulations, they investigate the sequence of molecular assembly in NFAs. The study shows that molecules with higher energy density, such as ITIC and 4TIC, directly form crystalline structures, though variations in processing conditions lead to differences in crystallinity and order; in contrast, for the hierarchically assembled 6TIC acceptor, the molecule first forms two-dimensional layered structures and, under the influence of the DIO additive, further develops a three-dimensional crystalline structure. These differences in intermolecular forces determine how well NFA molecules maintain their crystalline phases in blended films. In blended films, the presence of donor polymers and acceptor molecules generally reduces the crystallinity of NFAs; however, the use of the DIO additive can enhance NFA crystallinity, and strong intermolecular interactions help preserve the crystalline morphology. Notably, even when prepared under DIO conditions, 6TIC maintains its two-dimensional layered packing due to its hierarchical assembly. Figure 3. GIWAXS patterns of pure films and the assembly process of molecular crystallization in pure films. Furthermore, ultrafast transient absorption spectroscopy (TA) is used to probe the photophysical properties of blended films, with long-wavelength laser excitation directed specifically at the NFA acceptor. In the TA spectrum of an ITIC pure film, an excited-state signal at 955 nm and a polaron signal at 1335 nm can be observed. In pure films prepared under DIO conditions, excitons convert more rapidly into polarons, indicating that the crystalline phase of NFAs harbors a spontaneous exciton-dissociation pathway that does not rely on exciton dissociation at the donor–acceptor interface—a novel mechanism for charge carrier formation. Similar results are also seen in the TA spectra of 4TIC and 6TIC pure films. Moreover, the decay curve of polarons in 6TIC pure films exhibits a broad plateau (with a lifetime exceeding 1000 ps), suggesting that 6TIC’s two-dimensional structure is conducive to accommodating separated polarons. In the TA spectra of blended films, polarons can be detected as early as 0 fs, alongside evidence of hole transfer from the NFA acceptor to the donor material. In DIO-prepared blended films, the yield of polarons increases and the rate of hole transfer accelerates. Quantitative comparisons reveal that, at 0 fs, the interfacial polaron yield in blended films is comparable to the spontaneous polaron yield, underscoring the importance of both charge-generation pathways in non-fullerene donor–acceptor blended films. Device data further indicate that broadening the absorption range of NFA materials enhances device current, while increasing CT-state energy and reducing CT-state density helps minimize non-radiative losses and improve open-circuit voltage. Together with the spontaneous carrier-generation pathway, these findings provide a more comprehensive explanation of the photoelectric conversion process in organic photovoltaics. Figure 4. Ultrafast spectroscopy of blended films, polaron lifetimes, polaron yields, and a schematic illustration of the photophysical processes involved. Figure 5. Fitting of the CT state in blended films, along with EL spectra of pure and blended films. In summary, this work provides an in-depth exploration of the crystalline structures and self-assembly processes of NFA molecules, analyzes the influence of intermolecular forces on orderly molecular assembly, establishes a systematic methodology for studying NFA crystals and thin-film morphologies, and elucidates the dual-channel charge-generation mechanism in non-fullerene organic photovoltaic cells. These findings offer new insights into the structure of organic photovoltaic materials and their photoelectric conversion processes, thereby facilitating the development of novel materials.
03-21
Xing Jun et al., Nat. Commun.: Molecular Engineering of High-Efficiency White Perovskite LEDs
Low-dimensional hybrid perovskites exhibit outstanding performance as white-light emitters. Broadband white-light emission originates from self-trapped excitons (STEs). However, the formation mechanism of STEs in perovskites remains poorly understood, and the synthesis of new low-dimensional white perovskites has thus relied primarily on screening large libraries of organic intercalants rather than on rational molecular design.
2021
08-16
