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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

2022

12-02