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Organic solar cells (OSCs) have attracted much interest in the past few decades because of their advantages, such as being lightweight, low cost, simple preparation process, and environmental friendliness. While researchers have made significant progress on the active layer materials of OSCs, the interface engineering is another entry point for upgrading the photovoltaic performance of OSCs. Significantly, the interface modification materials, including anode interfacial materials and cathode interfacial materials, are two essential parts of interfacial layers for OSCs, in which the excellent interfacial materials can realize the very high‐performance photovoltaic cells. Among these interfacial materials, the anode interfacial layers (AILs) play a crucial role in improving photovoltaic performance. This review expresses a detailed conclusion of the development of anode interfacial materials and an outlook on future trends for OSCs. [ABSTRACT FROM AUTHOR]

The selection of photoactive layer materials for organic solar cells (OSCs) is essential for the photoelectric conversion process. It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis. However, there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions. Therefore in this study we utilize a chlorophyll derivative, Ce6Me3, as a donor material and investigate the performance of its heterojunction with acceptor materials. Through density functional theory, the photoelectric performances of acceptors, including the fullerene derivative PC71BM and the terminal halogenated non-fullerene DTBCIC series, are compared in detail. It is found that DTBCIC-Cl has better planarity, light absorption, electron affinity, charge reorganization energy and charge mobility than others. Ce6Me3 has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties. Furthermore, the designed Ce6Me3/DTBCIC interfaces have improved charge separation and reorganization rates (K CS/ K CR) compared with the Ce6Me3/PC71BM interface. This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have demonstrated over 19% power conversion efficiency (PCE) with the help of material innovation and device optimization. Co‐working with newly designed materials, traditional solvent additives, 1‐chloronaphthalene (CN), and 1,8‐diodooctane (DIO) are still powerful in morphology modulation towards satisfying efficiencies. Here, we chose recently reported high‐performance polymer donors (PM6 & D18‐Fu) and small molecular acceptors (Y6 & L8‐BO) as active layer materials and processed them by different conditions (CN or DIO or none). Based on corresponding 12 groups of device results, and their film morphology characterizations (both ex‐situ and in‐situ ones), the property‐performance relationships are revealed case by case. It is thereby supposed to be taken as a successful attempt to demonstrate the importance and complexity of donor‐acceptor‐additive interaction, since the device performance and physics analyses are also tightly combined with morphology variation. Furthermore, ternary blend construction for PCE improvement provides an approaching 19% level and showcases the potential of understanding‐guided‐optimization (UGO) in the future of OSCs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) are considered as a crucial energy source for flexible and wearable electronics. Pseudo-planar heterojunction (PPHJ) OSCs simplify the solution preparation and morphology control. However, non-halogenated solvent-printed PPHJ often have an undesirable vertical component distribution and insufficient donor/acceptor interfaces. Additionally, the inherent brittleness of non-fullerene small molecule acceptors (NFSMAs) in PPHJ leads to poor flexibility, and the NFSMAs solution shows inadequate viscosity during the printing of acceptor layer. Herein, we propose a novel approach termed polymer-incorporated pseudo-planar heterojunction (PiPPHJ), wherein a small amount of polymer donor is introduced into the NFSMAs layer. Our findings demonstrate that the incorporation of polymer increases the viscosity of acceptor solution, thereby improving the blade-coating processability and overall film quality. Simultaneously, this strategy effectively modulates the vertical component distribution, resulting in more donor/acceptor interfaces and an improved power conversion efficiency of 17.26%. Furthermore, PiPPHJ-based films exhibit superior tensile properties, with a crack onset strain of 12.0%, surpassing PPHJ-based films (9.6%). Consequently, large-area (1 cm2) flexible devices achieve a considerable efficiency of 13.30% and maintain excellent mechanical flexibility with 82% of the initial efficiency after 1000 bending cycles. These findings underscore the significant potential of PiPPHJ-based OSCs in flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

Reducing the voltage loss (ΔVloss) and thus increasing the open-circuit voltage (VOC) are key factors to further improve the photovoltaic performance of organic solar cells (OSCs). For A–DA′D–A-type acceptors, the above goals could be achieved through the regulation of the central A′ core and terminal groups. Hence, a novel A′–A–DA′D–A–A′ type acceptor named BTA79 was developed, where the benzotriazole (BTA) unit was used as the A′ unit on both the central core and the terminal groups. Two BTA-based polymers, J52 and J52-Cl, were used as donors to fabricate OSCs. A J52:BTA79-based device realized a power conversion efficiency of 10.71%, with a VOC of 0.93 V and a nonradiative recombination voltage loss (ΔVnon-rad) of 0.23 V. Interestingly, the J52-Cl:BTA79 system showed a lower ΔVnon-rad of 0.18 V but an inferior efficiency of 2.48%. This design of the A′–A–DA′D–A–A′-type acceptor provides a key reference for the development of high VOC acceptors for OSCs. [ABSTRACT FROM AUTHOR]

Unfused-ring non-fullerene acceptors (UF-NFAs) have garnered substantial attention because of their simple chemical structure and easy synthesis, making them promising candidates for advancing the application of organic solar cells (OSCs). The design and synthesis of UF-NFAs with upshifted lowest unoccupied molecular orbitals (LUMOs) can improve the open-circuit voltage (VOC) and thus the photovoltaic performance of devices. Herein, we developed three UF-NFAs, namely, BPD-H, BPD-F, and BPD-Cl, using the phthalimide electron-deficient unit as the building block. Because of the stronger electron-withdrawing effect of chlorine atoms, BPD-Cl exhibited higher molar extinction coefficients and red-shifted absorption than BPD-H or BPD-F. Additionally, the PM6:BPD-Cl-based blended film displayed highly efficient exciton separation, better charge transportation, and an appropriate active layer morphology. Thus, PM6:BPD-Cl-based OSCs achieved a higher PCE of 10.72%, outperforming PM6:BPD-H-based (6.44%) and PM6:BPD-F-based (7.98%) devices. Our findings indicate that choosing the phthalimide electron-deficient unit as the building block and modifying terminal groups are promising strategies for fabricating efficient UF-NFAs. [ABSTRACT FROM AUTHOR]

The rapid development of photovoltaic technology has driven the search for novel materials that can improve the cost-effectiveness and efficiency of solar cells. Organic semiconductors offer unique optical tunability and transparency, allowing customization for the absorption of specific optical spectra like near-infrared radiation. Through the molecular engineering of electron donors and acceptors, these materials can be optimized for targeted optical selectivity. This adaptability enables the development of efficient energy-harvesting devices tailored for specific spectral regions. Consequently, organic semiconductors present a promising avenue for specialized applications such as semi-transparent organic solar cells. This review offers a detailed summary of the latest developments in novel organic semiconductor materials, focusing on design principles and synthesis of materials in the context of semi-transparent organic solar cells. Optimization of molecular architecture, photovoltaic performance, and the optoelectronic properties of these materials has been explored, highlighting their potential for next-generation solar energy conversion. [ABSTRACT FROM AUTHOR]

The two-step layer-by-layer (LBL) deposition of donor and acceptor films enables desired vertical phase separation and high performance in organic solar cells (OSCs), which becomes a promising technology for large-scale printing devices. However, limitations including the use of toxic solvents and unpredictable infiltration between donor and acceptor still hinder the commercial production of LBL OSCs. Herein, we developed a water-based nanoparticle (NP) ink containing donor polymer to construct a mesoscale structure that could be infiltrated with an acceptor solution. Using non-halogen o-xylene for acceptor deposition, the LBL strategy with a mesoscale structure delivered outstanding efficiencies of 18.5% for binary PM6:L8-BObased LBL OSCs. Enhanced charge carrier mobility and restricted trap states were observed in the meso-LBL devices with optimized vertical morphology. It is believed that the findings in this work will bring about more research interest and effort on eco-friendly processing in preparation for the industrial production of OSCs. [ABSTRACT FROM AUTHOR]

In recent years, organic molecules have been the subject of in-depth research studies using in silico methods for their applications in solar cells and photonic devices. This study reports a theoretical investigation of the organic solar cell (OSC) and nonlinear optical (NLO) properties of (E)-1-(phthalazin-1-yl)-1-[(pyridin-2-yl)ethylidene]hydralazine (PPEH) and 1-[2-(1-(pyridine-3- yl)ethylidene)hydrazinyl]phthalazine (PEHP). The density functional theory (DFT) and its time-dependent extension (TD-DFT) were employed with the B2PLYP, M06-2X, BP86, CAM-B3LYP, and ω B97-XD functionals, alongside the def2-tzvp and def2-tzvpp basis sets. Geometrical and Frontier molecular orbital (FMO) analyses were performed. Reactivity descriptors, open circuit voltage (Voc), energy driving force (∆EL−L), light harvesting efficiencies (LHEs), NLO susceptibilities, and properties were also computed and discussed. The results show that PEPH and PPEH are good electron donor materials for organic solar cells as they possess high FMO energies, Vocs, ∆EL−Ls, and LHEs. Moreover, both molecules have static first and second hyperpolarizabilities as well as dynamic NLO responses that are on average 10 times greater than those of para-nitroaniline. PEPH and PPEH also exhibit properties such as second harmonic generation (SHG), electro-optic Pockels effect (EOPE), electric field-induced second harmonic generation (EFISHG), and optical Kerr effect (OKE). Indeed, these molecules are potential candidates for organic solar cells and NLO applications. Findings from this work may further accelerate the synthesis and development of green energy materials for optical solar cells and NLO applications in the future. [ABSTRACT FROM AUTHOR]

The impact of photovoltaic (PV) systems on distribution networks in advances of cloud, grid, and cluster computing was annoying in the study. Additional PV systems are explained with their working principles. Furthermore, A clustering-based model was developed to reduce the error in the calculation. The weather conditions were classified into different synoptic types. Prediction-based models were introduced after classifying the weather conditions in different optic types. For the movie, it was noted that conditions play a Vital role in predicting the output produced by a PV system. Moreover, a coherent discussion about the key elements regarding the impact of PV systems on Distribution Networks for Cloud, Grid, and Cluster Computing is done. Thus, through the discussion, an empirical knowledge-based analysis was presented. [ABSTRACT FROM AUTHOR]

To achieve maximum efficiency in organic photovoltaics (OPV), functional layers with uniform and exactly predefined thickness are required. An in-depth understanding of the coating process is therefore crucial for an accurate process control. In this paper, the meniscus-guided blade coating process, which is the most commonly used process for the manufacturing of organic electronics, is investigated by experimental and numerical methods. A computational fluid dynamics (CFD) model is created to simulate the coating behaviour of P3HT:O IDTBR, an industrial state-of-the-art active material system used in OPV, and its results' independence of numerical parameters is ensured. In particular, the influence of the coating velocity and the initially injected fluid volume on the resulting wet film thickness is studied. The developed CFD analysis is able to reproduce the experimental results with very high accuracy. It is found that the film thickness follows a power law dependence on the velocity (~v2/3) and a linear dependence on the ink volume (~V). Accordingly, an analytical expression based on our theoretical considerations is presented, which predicts the wet film thickness as a function of the coating velocity and the ink volume only based on easily accessible ink properties. Consequently, this CFD model can effectively substitute time-consuming and expensive experiments, which currently have to be performed manually in the laboratory for a multitude of novel material systems, and thus supports highly accelerated material research. Moreover, the results of this work can be used to achieve homogeneous large-area coatings by utilising accelerated blade coating. [ABSTRACT FROM AUTHOR]

Significant progress has been made in the advancement of perovskite solar cells, but their commercialization remains hindered by their lead-based toxicity. Many non-toxic perovskite-based solar cells have demonstrated potential, such as Cs2AgBi0.75Sb0.25Br6, but their power conversion efficiency is inadequate. To address this issue, some researchers are focusing on emerging acceptor–donor–acceptor'–donor–acceptor (A-DA'D-A)-type non-fullerene acceptors (NFAs) for Cs2AgBi0.75Sb0.25Br6 to find effective electron transport layers for high-performance photovoltaic responses with low voltage drops. In this comparative study, four novel A-DA'D-A-type NFAs, BT-LIC, BT-BIC, BT-L4F, and BT-BO-L4F, were used as electron transport layers (ETLs) for the proposed devices, FTO/PEDOT:PSS/Cs2AgBi0.75Sb0.25Br6/ETL/Au. Comprehensive simulations were conducted to optimize the devices. The simulations showed that all optimized devices exhibit photovoltaic responses, with the BT-BIC device having the highest power conversion efficiency (13.2%) and the BT-LIC device having the lowest (6.8%). The BT-BIC as an ETL provides fewer interfacial traps and better band alignment, enabling greater open-circuit voltage for efficient photovoltaic responses. [ABSTRACT FROM AUTHOR]

Organic photovoltaics (OPV) are one of the most effective ways to harvest renewable solar energy, with the power conversion efficiency (PCE) of the devices soaring above 19 % when processed with halogenated solvents. The superior photocurrent of OPV over other emerging photovoltaics offers more opportunities to further improve the efficiency. Tailoring the absorption band of photoactive materials is an effective way to further enhance OPV photocurrent. However, the field has mostly been focusing on improving the near‐infrared region photo‐response, with the absorption shoulders in short‐wavelength region (SWR) usually being neglected. Herein, by developing a series of non‐fullerene acceptors (NFAs) with varied side‐group conjugations, we observe an enhanced SWR absorption band with increased side‐group conjugation length. The underpinning factors of how molecular structures and geometries improve SWR absorption are clearly elucidated through theoretical modelling and crystallography. Moreover, a clear relationship between the enhanced SWR absorption and reduced singlet‐triplet energy gap is established, both of which are favorable for the OPV performance and can be tailored by rational structure design of NFAs. Finally, the rationally designed NFA, BO‐TTBr, affords a decent PCE of 18.5 % when processed with a non‐halogenated green solvent. [ABSTRACT FROM AUTHOR]

Highlights: Alkyl-tailored Y-SMAs named YR-SeNF series with near-infrared absorption, different molecular crystallinity and self-assembly abilities are developed. The related organic solar cells (OSCs) with an active layer processed from halogen-free solvents and spin-coating-free technologies achieve a ~ 19% efficiency. Ternary OSCs offer a robust operating stability under MPP tracking and well-keep > 80% of the initial efficiency for even over 400 h. Power-conversion-efficiencies (PCEs) of organic solar cells (OSCs) in laboratory, normally processed by spin-coating technology with toxic halogenated solvents, have reached over 19%. However, there is usually a marked PCE drop when the blade-coating and/or green-solvents toward large-scale printing are used instead, which hampers the practical development of OSCs. Here, a new series of N-alkyl-tailored small molecule acceptors named YR-SeNF with a same molecular main backbone are developed by combining selenium-fused central-core and naphthalene-fused end-group. Thanks to the N-alkyl engineering, NIR-absorbing YR-SeNF series show different crystallinity, packing patterns, and miscibility with polymeric donor. The studies exhibit that the molecular packing, crystallinity, and vertical distribution of active layer morphologies are well optimized by introducing newly designed guest acceptor associated with tailored N-alkyl chains, providing the improved charge transfer dynamics and stability for the PM6:L8-BO:YR-SeNF-based OSCs. As a result, a record-high PCE approaching 19% is achieved in the blade-coating OSCs fabricated from a green-solvent o-xylene with high-boiling point. Notably, ternary OSCs offer robust operating stability under maximum-power-point tracking and well-keep > 80% of the initial PCEs for even over 400 h. Our alkyl-tailored guest acceptor strategy provides a unique approach to develop green-solvent and blade-coating processed high-efficiency and operating stable OSCs, which paves a way for industrial development. [ABSTRACT FROM AUTHOR]

Based on the PM6:Y6 binary system, a novel non-fullerene acceptor material, D18-Cl, was doped into the PM6:Y6 blend to fabricate the active layer. The effects of different doping ratios of D18-Cl on organic solar cells were investigated. The best-performing organic solar cell was achieved when the doping ratio of D18-Cl reached 20 wt%. It exhibited a short-circuit current of 28.13 mA/cm2, a fill factor of 70.25%, an open-circuit voltage (Voc) of 0.81 V, and a power conversion efficiency of 16.08%. The introduction of an appropriate amount of D18-Cl expanded the absorption spectrum of the active layer, improved the morphology of the active layer, reduced large molecular aggregation and defects, minimized bimolecular recombination, and optimized the collection efficiency of charge carriers. These results indicate the critical importance of selecting an appropriate third component in binary systems and optimizing the doping ratio to enhance the performance of ternary organic solar cells. [ABSTRACT FROM AUTHOR]

Currently, most of the disclosed ternary strategies to improve photovoltaic performance of all‐polymer solar cells (all‐PSCs) commonly focus on the guest polymers having similar structures with the host polymer donors or acceptors. Herein, this work develops a distinctive ternary method that adding an amorphous B←N embedded polymer named BN‐Cl‐2fT to a crystallized host polymer blend of PM6 (a commercialized polymer donor) and PY‐TT (a copolymer of Y6 and thieno[3,2‐b]thiophene). Although the structures between BN‐Cl‐2fT and PM6 and PY‐TT are completely different, excellent miscibility is found between BN‐Cl‐2fT and both of the host PM6 and PY‐TT, which can be interpreted by the crowded phenyl groups anchoring along the backbone of BN‐Cl‐2fT, leading to weak self‐aggregation. Glazing incidence wide‐angle X‐ray diffraction (GIWAXS) measurements explicitly confirm the crystallization of PM6 and PY‐TT and amorphous feature of BN‐Cl‐2fT. Furthermore, adding 10 wt% BN‐Cl‐2fT to PM6:PY‐TT can significantly enhance the crystallization of the host polymers. Thus the ternary devices based on PM6:PY‐TT:BN‐Cl‐2fT afford promote short‐circuit current density (JSC, 23.29 vs. 21.80 mA cm−2), fill factor (FF, 62.4% vs. 60.0%), and power conversion efficiency (PCE, 13.70% vs. 12.23%) in contrast to these parameters of binary devices based on PM6:PY‐TT. This work provides a unique and enlightening avenue to design high performance all‐PSCs by adding amorphous B←N embedded polymers as guest component to enhance host‐crystallization. [ABSTRACT FROM AUTHOR]

Using the density functional theory (DFT), the influence of substitution of electron-donating (OCH3 and OH) and electron-accepting (F and Cl) groups on the peripheral thiophene units of DRTB-T donor molecule is studied. By optimizing the geometric structure, HOMO and LUMO energies, reorganization energies, optical properties, and photovoltaic properties are simulated. It is found that the ionization potential of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) reduces, but it increases for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with that of DRTB-T. It is also found that the absorption spectra of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) get redshifted, but these get blue shifted for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with those of DRTB-T. These changes in the electronic and optical properties of the modified structures result in higher PCE in BHJ OSCs with the blended active layer of DRTB-4F: NITI, DRTB-4Cl: NITI, in comparison with that of OSC with the active layer of DRTB-T: NITI and the highest being 15.0% in DRTB-4Cl: NITI. Our results may be expected to provide valuable insights into design optimization, leading to the fabrication of more efficient OSCs. [ABSTRACT FROM AUTHOR]

All‐polymer solar cells (all‐PSCs), using polymerized non‐fullerene acceptors (PNFAs), have shown promise in improving device stabilities compared to small‐molecular acceptor‐based PSCs. However, low mixing entropy between polymer donors (PDs) and PNFAs hampers the development of optimized blend morphology. Herein, this study develops efficient conjugated polymers that serve as interfacial compatibilizers between host PD and PNFA. Ternary all‐polymer blends containing the compatibilizer demonstrate improved blend morphology with strengthened interfaces, resulting in better photovoltaic properties and thermal/mechanical stabilities. In detail, the power conversion efficiency (PCE) increases from 15.4 to 17.1% upon the addition of the compatibilizer. Moreover, the devices based on the ternary blend enable good thermal stability, retaining 90% of the initial PCE after 96 h at 125 °C. Additionally, the mechanical properties are improved; the cohesive fracture energy (Gc) of 2.6 J m−2 and crack onset strain (COS) of 20.4% of the ternary blend outperform those of the binary blend (Gc = 1.1 J m−2 and COS = 16.5%). Resultingly, the stretchable PSCs based on the ternary blend exhibit an excellent PCE of 13.7% and stretchability with a strain at PCE80% of 35%. [ABSTRACT FROM AUTHOR]

Developing photovoltaic materials well balancing efficiency, stability, and cost is highly required for organic solar cells (OSCs) moving toward commercial applications. With such intention, two nonfused ring electron acceptors (NFREAs), 3TT11‐4F and 3TT46‐4F, with large steric hindrance substituents and linear/branched alkyl side chains are designed. The change of alkyl side chains from branched to linear leads to tighter π–π stacking and uniform molecular orientation for 3TT11‐4F, as revealed in single‐crystal structure, which further boosts the charge transport and regulates the aggregation property. Thus, a better efficiency of 15.02% is achieved in 3TT11‐4F‐based OSC with significantly improved photocurrent, relative to 3TT46‐4F‐based one (13.79%). Besides, the two NFREAs also enable good device stability with over 70% initial efficiencies maintained after 800 h illumination. Considering the low synthetic complexity, a high industrial figure‐of‐merit value of 16.34% is achieved for 3TT11‐4F‐based OSC, superior to some typical counterparts. The work provides a good reference for material design with an outstanding figure‐of‐merit. [ABSTRACT FROM AUTHOR]

The combination of UV-ozone and Al-doping enhancements in the ZnO ETL layer was studied for fullerene-based (P3HT:PCBM) and nonfullerene-based (J71:m-ITIC) solar cells. The study focused on morphological and interfacial defects and their relation to the electrical and optical properties of different Al-doped ZnO layers. The study also investigated the surface recombination velocity at the interface of the ZnO/active layer, as well as the carrier lifetime and diffusion length of the active layer theoretically. The most effective Al-doping dosage was 3% for P3HT:PCBM and 2% for J71:m-ITIC, attributed to the varying sensitivity of the active layer materials to morphological enhancement. [ABSTRACT FROM AUTHOR]

Recently, non-fullerene-based organic solar cells (OSCs) have made great breakthroughs, and small structural differences can have dramatic impacts on the power conversion efficiency (PCE). We take ITIC and its isomers as examples to study their effects on the performance of OSCs. ITIC and NFBDT only differed in the side chain position, and they were used as models with the same donor molecule, PBDB-T, to investigate the main reasons for the difference in their performance in terms of theoretical methods. In this work, a detailed comparative analysis of the electronic structure, absorption spectra, open circuit voltage and interfacial parameters of the ITIC and NFBDT systems was performed mainly by combining the density functional theory/time-dependent density functional theory and molecular dynamics simulations. The results showed that the lowest excited state of the ITIC molecule possessed a larger ∆q and more hybrid FE/CT states, and PBDB-T/ITIC had more charge separation paths as well as a larger kCS and smaller kCR. The reason for the performance difference between PBDB-T/ITIC and PBDB-T/NFBDT was elucidated, suggesting that ITIC is a superior acceptor based on a slight modulation of the side chain and providing a guiding direction for the design of superior-performing small molecule acceptor materials. [ABSTRACT FROM AUTHOR]

We prepared ternary organic solar cells (OSCs) by incorporating the medium wavelength absorption polymer PSEHTT into the PM6:L8-BO binary system. The power conversion efficiency (PCE) is improved from 15.83% to 16.66%. Although the fill factor (FF) is slightly reduced, the short-circuit current density (JSC) and open-circuit voltage (VOC) are significantly increased at the same time. A small amount of PSEHTT has a broad absorption spectrum in the short wavelength region and has good compatibility with PM6, which is conducive to fine-tuning the photon collection and improving the JSC. In addition, the highest occupied molecular orbital (HOMO) energy level of PSEHTT is deeper than that of PM6, which broadens the optical bandgap. This study provides an effective method to fabricate high-performance ternary OSCs by using a lower concentration of PSEHTT with PM6 as a hybrid donor material, which ensures a better surface and bulk morphology, improves photon collection, and broadens the optical bandgap. [ABSTRACT FROM AUTHOR]

In this study, an organic bulk heterojunction (BHJ) solar cell with a spiro OMeTAD as a hole transport layer (HTL) and a PDINO as an electron transport layer (ETL) was simulated through the one-dimensional solar capacitance simulator (SCAPS-1D) software to examine the performance of this type of organic polymer thin-film solar cell. As an active layer, a blend of polymer donor PBDB-T and non-fullerene acceptor ITIC-OE was used. Numerical simulation was performed by varying the thickness of the HTL and the active layer. Firstly, the HTL layer thickness was optimized to 50 nm; after that, the active-layer thickness was varied up to 80 nm. The results of these simulations demonstrated that the HTL thickness has rather little impact on efficiency while the active-layer thickness improves efficiency significantly. The temperature effect on the performance of the solar cells was considered by simulations performed for temperatures from 300 to 400 K; the efficiency of the solar cell decreased with increasing temperature. Generally, polymer films are usually full of traps and defects; the density of the defect (Nt) value was also introduced to the simulation, and it was confirmed that with the increase in defect density (Nt), the efficiency of the solar cell decreases. After thickness, temperature and defect density optimization, a reflective coating was also applied to the cell. It turned out that by introducing the reflective coating to the back side of the solar cell, the efficiency increased by 2.5%. Additionally, the positive effects of HTL and ETL doping on the efficiency of this type of solar cells were demonstrated. [ABSTRACT FROM AUTHOR]

The research for efficient organic materials organized in bulk heterojunction (BHJ) thin films for organic photovoltaics (OPVs) has shown a significant breakthrough in the past decade. Desired structural organization can be attained through various strategies. In this regard, the current review highlights tuning of alkyl chains introduced on molecular structures of active materials. The recent wide literature is classified based on the introduction of alkyl chains on polymers and small molecules used as donor and acceptor materials. The design of these materials, the morphological aspects of the active layers, and the performances of the related photovoltaic cells are detailed. A comprehensive discussion on chemical structures of the different material families considered, their modification by alkyl chains of various natures, and the morphological aspects are reported and tabulated. [ABSTRACT FROM AUTHOR]

Achieving both high open‐circuit voltage (Voc) and short‐circuit current density (Jsc) to boost power‐conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (Eloss) and inefficient charge transfer usually take place. Here, three new Y‐series acceptors of mono‐asymmetric asy‐YC11 and dual‐asymmetric bi‐asy‐YC9 and bi‐asy‐YC12 are developed. They share the same asymmetric D1AD2 (D1=thieno[3,2‐b]thiophene and D2=selenopheno[3,2‐b]thiophene) fused‐core but have different unidirectional sidechain on D1 side, allowing fine‐tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi‐asy‐YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy‐YC9 and PM6 : bi‐asy‐YC11 ones. Therefore, the PM6 : bi‐asy‐YC12‐based OSCs offer a higher PCE of 17.16 % with both high Voc and Jsc, due to the reduced Eloss and efficient charge transfer properties. Inspired by the high Voc and strong NIR‐absorption, bi‐asy‐YC12 is introduced into efficient binary PM6 : L8‐BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized Eloss, the PM6 : L8‐BO : bi‐asy‐YC12‐based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing‐free devices. Our developed unidirectional sidechain engineering for constructing bi‐asymmetric Y‐series acceptors provides an approach to boost PCE of OSCs. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effects of different acceptors (IT−4F and PC71BM) on the charge dynamics in PM6-based solar cells. The correlation between different acceptors and the performance of organic solar cells was studied by atomic force microscope, steady-state absorption spectrum, transient absorption spectrum, and electrical measurements. Optical absorption exhibited that IT−4F has strong absorption in the near-infrared region for the active layer. Transient absorption measurements showed that different acceptors (IT−4F and PC71BM) had a significant influence on the behaviors of PM6 excitons and charge dynamics. That is, the exciton dissociation rate and delocalized polaron transport in the PM6:IT−4F active layer were significantly faster than that in the PM6:PC71BM active layer. The lifetime of localized polaron in the PM6:PC71BM active layer was longer than that in the PM6:IT−4F active layer. Conversely, the lifetime of delocalized polaron in the PM6:IT−4F active layer was longer than that in the PM6:PC71BM active layer. Electrical measurement analysis indicated that lower bimolecular recombination, higher charge transport, and charge collection ability were shown in the PM6:IT−4F device compared with the PM6:PC71BM device. Therefore, PM6:IT−4F solar cells achieved a higher power conversion efficiency (12.82%) than PM6:PC71BM solar cells (8.78%). [ABSTRACT FROM AUTHOR]

All‐polymer solar cells (all‐PSCs) have promising potential for industrial production due to their superior stability. Recently, the widespread application of the polymerized small molecule acceptor (PSMA) has led to a surge in the efficiency of all‐PSCs. However, the high efficiencies of these devices generally rely on the use of the highly volatile solvent, chloroform (CF). Furthermore, the molecular weights of PSMA are lower than polymer donors, yet their crystallinity is weaker than typical small molecules, making most PSMA‐based all‐PSCs suffer from low electron mobility. To improve device performance and facilitate large scale production of all‐PSCs, it is necessary to enhance electron mobility and avoid the use of CF. This paper investigates the use of sequential processing (SqP) for active layer preparation using toluene as the solvent to address these issues. This work reports 18.1% efficient all‐PSC devices, which is the highest efficiency of all‐PSCs prepared using non‐halogen solvents. This work systematically compares the conventional blend‐casting method with the SqP method using PM6 as the donor and PY‐V‐γ and PJ1‐γ as the acceptors, and compares the performance of binary and ternary blends in both methods. Finally, this work measures the device stability and finds that SqP can significantly improve the photostability of the device. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have gained increasing attention. Among the various directions in OSCs, all-polymer solar cells (all-PSCs) have emerged as a highly promising and currently active research area due to their excellent film formation properties, mechanical properties, and thermal stabilities. However, most of the high-efficiency all-PSCs are processed from chloroform with an active layer thickness of ~100 nm. In order to meet the requirements for industrialization, a thicker active layer processed from low-vapor pressure solvents (preferentially a hydrocarbon solvent) is strongly desired. Herein, we employ toluene (a hydrocarbon solvent with a much higher boiling point than chloroform) and a method known as sequential processing (SqP) to mitigate the rapid decline in efficiency with increasing film thickness. We show that SqP enables a more favorable vertical phase segregation that leads to less trap-assisted recombination and enhanced charge extraction and lifetime than blend-cast devices at higher film thicknesses. [ABSTRACT FROM AUTHOR]

In this study, we present a comprehensive investigation into the charge generation mechanism in bulk-heterojunction organic solar cells employing non-fullerene acceptors (NFAs) both with and without the presence of processing additives. While photovoltaic devices based on Y6 or BTP-eC9 have shown remarkable power conversion efficiencies, the underlying charge generation mechanism in polymer:NFA blends remains poorly understood. To shed light on this, we employ transient absorption (TA) spectroscopy to elucidate the charge transfer pathway within a blend of the donor polymer PM6 and NFAs. Interestingly, the charge carrier lifetimes of neat Y6 and BTP-eC9 are comparable, both reaching up to 20 ns. However, the PM6:BTP-eC9 blend exhibits substantially higher charge carrier generation and a longer carrier lifetime compared to PM6:Y6 blend films, leading to superior performance. By comparing TA data obtained from PM6:Y6 or PM6:BTP-eC9 blend films with and without processing additives, we observe significantly enhanced charge carrier generation and prolonged charge carrier lifetimes in the presence of these additives. These findings underscore the potential of manipulating excited species as a promising avenue for further enhancing the performance of organic solar cells. Moreover, this understanding contributes to the advancement of NFA-based systems and the optimization of charge transfer processes in polymer:NFA blends. [ABSTRACT FROM AUTHOR]

Organic solar cells offer benefits such as transparent characteristics, affordability in manufacturing, and the ability to tailor light absorption properties according to specific needs. This review discusses challenges and recent strategies to enhance the power conversion efficiency of organic solar cells, such as bandgap tuning, molecular orbital alignment, active layer morphology engineering, electron-donating and -withdrawing group incorporation, side chain length engineering, a third additive's insertion, and control of the solubility of materials. The good transparency of organic solar cells makes them ideal for greenhouse-integrated photovoltaics applications. By efficiently absorbing sunlight for photosynthesis and clean energy production, transparent organic solar cells optimize light management, enhance energy efficiency, and minimize overheating risks, resulting in more sustainable and efficient greenhouse operations. This review also evaluates organic solar cell integration in the greenhouse. The implementation of the strategies explored in this review can significantly impact a wide range of performance parameters in organic solar cells. These parameters include the optoelectronic properties, absorption spectrum, open circuit voltage, exciton dissociation, charge transport, molecular packing, solubility, phase separation, crystallinity, nanoscale morphology, and device stability. An optimized organic solar cell design is particularly beneficial for greenhouse-integrated photovoltaics, as it ensures efficient energy conversion and energy management, which are crucial factors in maximizing the performance of the greenhouse. [ABSTRACT FROM AUTHOR]

The search for renewable and sustainable energy for energy security and better environmental protection against hazardous emissions from petro-based fuels has gained significant momentum in the last decade. Towards this end, energy from the sun has proven to be reliable and inexhaustible. Therefore, better light harvesting technologies have to be sought. Herein, the current trends in the development of perovskite solar cells with a focus on device engineering, band alignment, device fabrication with superior light harvesting properties, and numerical simulation of solar cell architectures are critically reviewed. This work will form the basis for future scientist to have a better scientific background on the design of highly efficient solar cell devices, which are cost-effective to fabricate, highly stable, and eco-friendly. This review presents thorough essential information on perovskite solar cell technology and tracks methodically their technological performance overtime. The photovoltaic (PV) technology can help to reduce pollution related to greenhouse gas emissions, criterion pollutant emissions, and emissions from heavy metals and radioactive species by nearly 90%. Following the introduction of highly efficient perovskite solar cell (PSC) technologies, the problems associated with stability, short life-time and lead-based perovskite solar cell configurations have significantly been minimized. The fabrication and simulation of perovskite solar cells has been made possible with advanced technologies and state-of-the-art computational codes. Furthermore, device simulation strategies have lately been used to understand, select appropriate materials, and gain insights into solar cell devices' physical behavior in order to improve their performances. Numerical simulation softwares such as the 1-dimenional solar cell capacitance simulator (SCAPS-1D), Silvaco ATLAS, and wx-analysis of microelectronic and photonic structures (wxAMPS) used to understand the device engineering of solar cells are critically discussed. Because of the need to produce charge collection selectivity, hole transport materials (HTMs) as well as electron transport materials (ETMs) constitute essential PSC components. In this work, the synthesis of inorganic HTMs, as well as their characteristics and uses in various PSCs comprising mesoporous and planar designs, are explored in detail. It is anticipated that the performance of inorganic HTLs on PSCs would encourage further research which will have a significant influence on the future designs and fabrication of highly efficient solar cells. [ABSTRACT FROM AUTHOR]

Given that bromine possesses similar properties but extra merits of easily synthesizing and polarizing comparing to homomorphic fluorine and chlorine, it is quite surprising very rare high-performance brominated small molecule acceptors have been reported. This may be caused by undesirable film morphologies stemming from relatively larger steric hindrance and excessive crystallinity of bromides. To maximize the advantages of bromides while circumventing weaknesses, three acceptors (CH20, CH21 and CH22) are constructed with stepwise brominating on central units rather than conventional end groups, thus enhancing intermolecular packing, crystallinity and dielectric constant of them without damaging the favorable intermolecular packing through end groups. Consequently, PM6:CH22-based binary organic solar cells render the highest efficiency of 19.06% for brominated acceptors, more excitingly, a record-breaking efficiency of 15.70% when further thickening active layers to ~500 nm. By exhibiting such a rare high-performance brominated acceptor, our work highlights the great potential for achieving record-breaking organic solar cells through delicately brominating. The relatively larger steric hindrance and excessive crystallinity of bromides could lead to undesirable film morphologies. Here, the authors take advantage of bromides and construct small molecule acceptors with stepwise bromination and realize maximum efficiency of 19% in organic solar cells. [ABSTRACT FROM AUTHOR]

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The advancement of non‐fullerene acceptors with crescent‐shaped geometry has led to the need for polymer donor improvements. Additionally, there is potential to enhance the photovoltaic parameters in high‐efficiency organic solar cells (OSCs). The random copolymerization method is a straightforward and effective strategy to further optimize photoactive morphology and enhance device performance. However, finding a suitable third component in terpolymers remains a crucial challenge. In this study, a series of terpolymer donors (PTF3, PTF5, PTF10, PTF20, and PTF50) is synthesized by introducing varying amounts of the trifluoromethyl‐substituted unit (CF3) into the PM6 polymer backbone. Even subtle changes in the CF3 content can significantly enhance all the photovoltaic parameters due to the optimized energy levels, molecular aggregation/miscibility, and bulk‐heterojunction morphology of the photoactive materials. Thus, the best binary OSC based on the PTF5:Y6‐BO achieves an outstanding power conversion efficiency (PCE) of 18.2% in the unit cell and a PCE of 11.6% in the sub‐module device (aperture size: 54.45 cm2), when using halogen‐free solvent o‐xylene. This work showcases the remarkable potential of the easily accessible CF3 unit as a key constituent in the construction of terpolymer donors in high‐performance OSCs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Constructing monolithic tandem solar cells (TSCs) is an effective method to break the Shockley–Queisser (S–Q) radiative efficiency limit for single‐junction solar cells. Employing the wide bandgap perovskite materials and low bandgap organic materials as absorber layers for front and rear subcells, respectively, to construct perovskite/organic TSCs can complementarily absorb sunlight in ultraviolet‐visible (UV‐Vis) range by front perovskite and near‐infrared (NIR) range by rear organic molecules, thus reducing the thermalization energy losses. Besides the subcells, the interconnection layer (ICL), which physically and electrically connects the front and rear subcells, is also an important tunnel junction to recombine charges. In this review, we summarize the optimization strategies of wide bandgap perovskites for front subcell, narrow bandgap organic material for rear subcell, and the ICLs employed in monolithic perovskite/organic TSCs. [ABSTRACT FROM AUTHOR]

With the development of organic solar cells (OSCs), the high‐performance and stable batch variance are becoming a new challenge for designing polymer donors. To obtain high photovoltaic performance, adopting polymers with high molecular weight as donors is an ordinary strategy. However, the high molecular weight need to subtly control the reaction time and state, inevitably caused batch‐to‐batch variations. Herein, a strategy of steric effect is applied to benzodifuran (BDF)‐based polymer by introducing different positions of Cl atom, producing two polymers PBDFCl‐1 and PBDFCl‐2. The more twisted side chains conformation not only achieve the control of moderate molecular weight for PBDFCl‐2, but also easily form molecular stacking through adopting BDF unit and maintain sufficient polymeric crystallinity. Due to the optimized stacking mode and good blend miscibility, PBDFCl‐2‐based device exhibitsa more elegant power conversion efficiency (PCE) of 17.00% compared to PBDFCl‐1‐based device. This is the highest efficiency record for BDF‐based binary OSCs. Meanwhile, the PCE device variation of the different molecular weights for PBDFCl‐2 is little, indicating the reduction of the batch variation. Therefore, smartly using steric effect of Cl atom in strong crystalline BDF unit can form efficient molecular stacking regulations and realize the coordination of high‐performance and stable batch variance. [ABSTRACT FROM AUTHOR]

One important subject in the field of all-polymer solar cells (all-PSCs) is the exploration of electron-deficient building blocks with optimized physicochemical properties to promote the performance of polymer acceptors. Here, two ladder-type heteroheptacene-containing small-molecule acceptors with branched 2-octyldodecyl or 2-hexyldecyl side-chains are synthesized and polymerized with the thiophene co-monomer to afford polymer acceptors (PW-OD and PW-HD) with strong near-infrared absorption. Experimental results reveal that the alkyl chain length has a large impact on the molecular packing behavior of the resulting polymers, which in turn affects their light-absorbing and charge transport properties, and thus the photovoltaic performance of the final devices. When blended with the polymer donor PM6, PW-HD-based all-PSCs deliver a higher power conversion efficiency (PCE) of 9.12% compared to the PCE of 6.47% for the PW-OD-based all-PSCs, mainly due to its more ordered inter-chain packing and more favorable blend morphology. This work provides a promising building block for the development of high-performance narrow-bandgap polymer acceptors and highlights the importance of side-chain substitution in optimizing the photovoltaic performance of polymer acceptors. [ABSTRACT FROM AUTHOR]

In recent years, due to the rapid development of high-performance small molecule acceptor (SMA) materials, the researches on p-type electron donor materials for matching with current efficient SMAs have become important. By means of asymmetric strategies to optimize the energy levels and inter/intramolecular interactions of molecules, we designed and synthesized an asymmetric aromatic side chain quinoxaline-based polymer donor TPQ-0F. Meanwhile, we took advantage of F atom which could form noncovalent interaction and strong electron-withdrawing property, to obtain the optimized quinoxaline-based polymer donors TPQ-1F, TPQ-1Fi and TPQ-2F. Eventually, the binary device based on TPQ-2F achieved an efficient power conversion efficiency (PCE) of 16.27%, which attributed to balanced hole/electron mobilities, less charge carrier recombination, and more favorable aggregation morphology. Our work demonstrates the great potential of asymmetric aromatic side chain quinoxaline-based polymer donors on optimizing the morphology of blending films, improving inter/intramolecular interactions, and subtly tuning energy level, finally for more efficient organic solar cells. [ABSTRACT FROM AUTHOR]

Developing high‐performance polymer donors is of great importance to further improve the photovoltaic performances of organic solar cells (OSCs). However, most polymer donors suffer from mismatching energy levels and poor batch‐to‐batch reproducibility, which hinder the further enhancement of device performance and their potential in a commercial application. Constructing random terpolymers with a third monomer is considered a practical way to solve these problems. Herein, the 5,6‐difluorobenzo[c][1,2,5]oxadiazole (ffBX) unit is incorporated into the skeleton of PBDB‐TF as the third comonomer to construct random terpolymers. The terpolymers exhibit downshifted the highest occupied molecular orbital energy levels than PBDB‐TF, which is beneficial for obtaining higher open‐circuit voltage and lower energy loss of the OSCs. The OSCs based on PBFBX20:Y6‐BO demonstrate high power conversion efficiency of 17.5%. Moreover, PBFBX20 exhibits excellent batch‐to‐batch reproducibility. Five polymer batches with molecular weights ranging from 20.0 to 54.0 kDa produced very similar PCEs. This work demonstrates the bright future of ffBX‐contained terpolymers in realizing high‐performance OSCs and further applying in the OSCs community. [ABSTRACT FROM AUTHOR]

Integrating a third component into the binary system is considered to be one of the most effective strategies to further enhance the power conversion efficiency (PCE) in organic solar cells (OSCs). Here, a novel perylene diimide (PDI) derivative featuring 3D structure, TPA‐4PDI, with tetraphenyladamantane central core is developed as a guest electron acceptor to be incorporated into the PM6:Y6 binary system. The champion PCE of ternary OSC is recorded to be 18.29% by adding 7.5 wt.% of TPA‐4PDI in the ternary blend, which photovoltaic performance is enhanced with synergistically increased open‐circuit voltage (Voc) of 0.849 V, short‐circuit current density (Jsc) of 27.55 mA cm−2, and fill factor (FF) of 78.21%. TPA‐4PDI exhibits a complementary absorption band with PM6 and Y6 while its lowest unoccupied molecular orbital (LUMO) energy level falls between the two host materials. The addition of TPA‐4PDI can effectively suppress the recombination behavior, inhibit the excessive aggregation of Y6 and improve the morphology of PM6:Y6 blend. All these effects function synergistically and then lead to the enhancement of Voc,Jsc, and FF in ternary OSCs. This study suggests that developing PDI derivatives as the third component is an effective method to further improve the performance of ternary OSCs. [ABSTRACT FROM AUTHOR]

Most cutting‐edge performance binary bulk heterojunction organic solar cells (OSCs) with high power conversion efficiency (PCE) over 18% generally use harmful halogenated solvent systems to guarantee the optimal morphology of active layers, urging more investigations on the non‐halogenated solvent processed OSCs and their further large‐scale devices fabrication. Herein, two BTP‐eC9 analogs, BTP‐eC9‐EH and BTP‐eC9‐HD, were synthesized to investigate the effect of alkyl chain length on the solubility and photovoltaic properties systematically. Despite the subtle side‐chain engineering, the PM6: BTP‐eC9‐HD based device exhibited an outstanding PCE of 17.5% and a remarkable fill factor of 79% in the toluene processing binary blend system, which precedes the toluene processing PM6: BTP‐eC9 based binary blend system (17.1%). The combined investigation provides a valuable insight into the modulation of branched alkyl chains, which can serve as an effective approach for adjusting the aggregation and molecular packing of A‐DA′DA‐type Y‐series based non‐fullerene acceptors to balance the materials solubility and solvents selection, thereby achieving high‐performance large‐scale OSCs processed from non‐halogenated solvents. [ABSTRACT FROM AUTHOR]

Third-generation solar cells are designed to achieve high power-conversion efficiency while being low-cost to produce. These solar cells have the ability to surpass the Shockley–Queisser limit. This review focuses on different types of third-generation solar cells such as dye-sensitized solar cells, Perovskite-based cells, organic photovoltaics, quantum dot solar cells, and tandem solar cells, a stacked form of different materials utilizing a maximum solar spectrum to achieve high power conversion efficiency. Apart from these solar cells, other third-generation technologies are also discussed, including up-conversion, down-conversion, hot-carrier, and multiple exciton. This review provides an overview of the previous work in the field, alongside an introduction to the technologies, including their working principles and components. Advancements made in the different components and improvements in performance parameters such as the fill factor, open circuit voltage, conversion efficiency, and short-circuit current density are discussed. We also highlight the hurdles preventing these technologies from reaching commercialization. [ABSTRACT FROM AUTHOR]

The power conversion efficiencies (PCEs) of organic photovoltaics (OPVs) have reached more than 19%, along with the prosperous development of materials and device engineering. It is meaningful to make a comprehensive review of the research of OPVs for further performance improvement. In this review, some typical materials of high-performance OPVs are summarized, including representative polymer donor materials, non-fullerene acceptor materials, and interfacial modification materials, as well as their design rules for molecular engineering. From the point of view of device engineering, active layer treatment and deposition technology are introduced, which can play a critical role in adjusting the degree of molecular aggregation and vertical distribution. Meanwhile, a ternary strategy has been confirmed as an efficient method for improving the performance of OPVs, and the multiple roles of the appropriate third component in the photo-electronic conversion process are emphasized and analyzed. The challenges and perspectives concerning this region are also put forward for further developing high-performance OPVs. [ABSTRACT FROM AUTHOR]

Tuning the properties of non‐fullerene acceptors (NFAs) through halogenation, including fluorination and chlorination, represents one of the most promising strategies to boost the performance of organic solar cells (OSCs). However, it remains unclear how the F and Cl choice influences the molecular packing and performance between small‐molecule and polymeric acceptors. Here, a series of small‐molecule and polymeric acceptors with different amounts and types of halogenation is synthesized, and the effects of fluorination and chlorination between small‐molecule and polymeric acceptors are investigated. It is found that chlorinated small‐molecule acceptors lead to longer exciton diffusion length and better performance compared to the corresponding fluorinated ones, which attributes to their stronger intermolecular packing mode. For polymer acceptors, in contrast, the fluorinated polymers achieve a denser packing mode and better performance, because chlorinated polymers exhibit reduced intrachain conjugation between end group moieties and linker units. This study demonstrates different halogenation effects on the packing modes and performances for small‐molecule and polymeric acceptors, which provides important guidance for the molecule design of high‐performance acceptors for OSCs. [ABSTRACT FROM AUTHOR]

Developing new polymerized small molecular acceptor (PSMA) is pivotal for improving the performance of all‐polymer solar cells. On the basis of this newly developed CH‐series small molecule acceptors, two PSMAs are reported herein (namely PZC16 and PZC17, respectively). To reduce the molecular torsion caused by the traditional aromatic π‐bridges, non‐aromatic conjugated units (ethynyl for PZC16 and vinylene for PZC17) are adopted as the linkers and their effect on the photo‐physical properties as well as the device performance are systematically investigated. Both polymer acceptors exhibit co‐planar molecular conformation, along with broad absorption ranges and suitable energy levels. In comparison with the PM6:PZC16 film, the PM6:PZC17 film exhibits more uniform phase separation in morphology with a distinct bi‐continuous network and better crystallinity. The PM6:PZC17‐binary‐based devices exhibit a satisfactory PCE of 16.33%, significantly higher than 9.22% of the PZC16‐based devices. Impressively, PM6:PZC17‐based large area device (ca. 1 cm2) achieves an excellent PCE of 15.14%, which is among the top performance for reported all‐polymer solar cells (all‐PSCs). [ABSTRACT FROM AUTHOR]

By changing the structures of the side chain on the backbone of the Y6 acceptor, many Y‐series acceptors have been synthesized to investigate the relationships between structures and properties of the fused‐ring electron acceptors (FREAs). However, not much attention has been paid to the effects of cycloalkane substituents on optoelectronic, morphological, and photovoltaic properties of the FREAs. Here, a brand‐new FREA D12 is developed by incorporating cyclohexylmethyl functional groups into the pyrrole rings of the backbone of the Y6 acceptor, and a similar compound E12 with the linear n‐heptane side chains is also synthesized for comparison. After the cyclization of the alkyl side‐chain, the molecular orientation of D12 exhibits favorable face‐on dominant, which endows D12 with higher charge mobility. Consequently, the organic solar cells (OSCs) with PM6 as donor and D12 as acceptor deliver the maximum power conversion efficiency of 17.3%, along with an excellent fill factor of 0.794, which is much higher than those of the PM6:E12‐based OSCs. The results reveal that introducing an inner cyclized alkyl chain on the pyrrole motif is a simple and feasible strategy to regulate molecular orientation and improve photovoltaic properties, which might provide guidelines for developing high‐performance electron acceptors. [ABSTRACT FROM AUTHOR]

The prerequisite for commercially viable organic solar cells (OSC) is to reduce the efficiency‐stability‐cost gap. Therefore, the cost of organic materials should be reduced by minimizing the synthetic steps, yet maintaining the molecular planarity and efficiencies achieved by the fused ring acceptors (FRA). In this respect, developing non‐fused ring acceptors (NFRA) with suitable functionalization to favor conformational planarity and effective molecular packing is beneficial and cost‐effective. Presently, the power conversion efficiency (PCE) for NFRAs is around 16 %, yet lower than the 19 % achieved for FRAs. Despite their potential, a thorough understanding of the effective structural design of NFRAs is necessary for developing efficient OSCs. This article pays special attention to the molecular design concept for NFRAs developed in the last years and analyzed the approach toward materials design and efficiency improvement, an important step toward technological application. [ABSTRACT FROM AUTHOR]

The elaborate balance between the open‐circuit voltage (VOC) and the short‐circuit current density (JSC) is critical to ensure efficient organic solar cells (OSCs). Herein, the chalcogen containing branched chain engineering is employed to address this dilemma. Three novel nonfullerene acceptors (NFAs), named BTP‐2O, BTP‐O‐S, and BTP‐2S, featuring different peripheral chalcogen containing branched chains are synthesized. Compared with symmetric BTP‐2O and BTP‐2S grafting two alkoxy or alkylthio branched chains, the asymmetric BTP‐O‐S grafting one alkoxy and one alkylthio branched chains shows mediate absorption range, applicable miscibility, and favorable crystallinity. Benefiting from the enhanced π–π stacking and charge transport, an optimal power conversion efficiency (PCE) of 17.3% is obtained for the PM6:BTP‐O‐S‐based devices, with a good balance between VOC (0.912 V) and JSC (24.5 mA cm−2), and a high fill factor (FF) of 0.775, which is much higher than those of BTP‐2O (16.1%) and BTP‐2S‐based (16.4%) devices. Such a result represents one of the highest efficiencies among the binary OSCs with VOC surpassing 0.9 V. Moreover, the BTP‐O‐S‐based devices fabricated by using green solvent yield a satisfactory PCE of 17.1%. This work highlights the synergistic effect of alkoxy and alkylthio branched chains for high‐performance OSCs by alleviating voltage loss and enhancing FF. [ABSTRACT FROM AUTHOR]

The active layer of all polymer solar cells (all-PSCs) is composed of a blend of a p-type conjugated polymer (p-CP) as donor and an n-type conjugated polymer (n-CP) as acceptor. All-PSCs possess the advantages of light weight, thin active layer, mechanical flexibility, low cost solution processing and high stability, but the power conversion efficiency (PCE) of the all-PSCs was limited by the poor photovoltaic performance of the n-CP acceptors before 2016. Since the report of the strategy of polymerized small molecule acceptors (PSMAs) in 2017, the photovoltaic performance of the PSMA-based n-CPs improved rapidly, benefitted from the development of the A-DA'D-A type small molecule acceptors (SMAs). PCE of the all-PSCs based on the PSMA acceptors reached 17%–18% recently. In this review article, we will introduce the development history of the n-CPs, especially the recent research progress of the PSMAs. Particularly, the structure-property relationship of the PSMAs is introduced and discussed. Finally, current challenges and prospects of the n-CP acceptors are analyzed and discussed. [ABSTRACT FROM AUTHOR]

The vinylene‐bridged helical perylene diimide (PDI) dimer (PDI2) with a build‐in twisted configuration is an alternative building block to the parent PDI for the construction of efficient non‐fullerene acceptor (NFAs). Moreover, it has been proved asymmetric strategy plays a vital role in the development of NFAs. Herein, we designed and synthesized a pair of acceptor‐donor‐acceptor (A−D‐A) type PDI2 derivatives, namely IDTIC‐PDI and IDT‐diPDI2, which contain asymmetric and symmetric end‐cap units, respectively. To determine the structure–performance relationships of asymmetric strategy, the organic solar cells (OSCs) based on these two molecules were fabricated and measured. The asymmetric IDTIC‐PDI based device exhibits a much higher PCE of 8.23 % than that of symmetric IDT‐diPDI2 (5.21 %). These results reveal that symmetry breaking provides an effective way to optimize the photovoltaic performances of PDI2 based OSCs. [ABSTRACT FROM AUTHOR]