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Thanks to the development of acceptor–donor–acceptor (A–D–A) type electron acceptors, organic solar cells (OSCs) have achieved marvelous progress in recent years. However, a systematic investigation about the structure–efficiency relationship is still highly desired to better understand the working mechanisms inside a bulk heterojunction (BHJ). In this study, new acceptors with the synergistic effect of side chain and unilateral π‐bridge strategy are designed, accounting for lower energy loss, expanded absorption, modulated intermolecular interactions and BHJ morphology. As a consequence, the resultant A–D–π–A acceptor ID‐C6Ph‐ST‐4F based binary solar cell receives an impressive efficiency up to 15.36%, much greater than the A–D–A analog ID‐C6Ph‐4F (10.75%), and ranks the best among all small molecular acceptors with symmetric or asymmetric π‐bridges. The results highlight the promising manipulation of phenylalkyl side chain and unilateral π‐bridge on intermolecular interactions among acceptor molecules and interactions between donor and acceptor (D/A) molecules. Superior interactions among acceptor molecules are an essential precondition to ensure preferable molecular assembly for charge transport, and meanwhile, moderately enhanced D/A interactions are also crucial for proper phase‐separation networks with efficient exciton dissociation and charge generation. [ABSTRACT FROM AUTHOR]

A new type of cathode interlayer composed of 2,6‐di‐tert‐butyl‐phenol‐functionalized perylene bisimide (PBI‐2P) is successfully applied as an electron transporting layer for fused‐ring nonfullerene organic solar cells (OSCs). The stable contact between these novel electron transporting layers and the representative nonfullerene acceptor Y6 greatly enhances the device stability compared to conventional amine‐group containing cathode interlayers. Moreover, the easily formed biradical species in the interlayers yields rather good thickness tolerance of the PBI‐2P layer in photovoltaic devices. The OSCs based on the PBI‐2P interlayer show a power conversion efficiency up to 17.20% and good stability compared to amino‐group functionalized interlayers. The findings demonstrate a promising design principle for cathode interlayer engineering based on pigment chromophores equipped with the 2,6‐di‐tert‐butylphenoxy groups that are prone to form the respective ultrastable butylphenoxy radicals for stable nonfullerene OSCs. [ABSTRACT FROM AUTHOR]

Promoted by uninterrupted materials and device innovation, organic solar cells have achieved impressive development. However, the complicated intermolecular interactions inside active layers are less understood. Herein, the intermolecular interactions are studied from the dual perspectives of acceptor/acceptor (A/A) and donor/acceptor (D/A), and how these interactions synergistically control the final efficiencies. Three small molecular acceptors (SMAs) are designed with different end‐caps, which manipulate the crystallinity and electrostatic potential (ESP) distributions of acceptors, and accordingly, the A/A and D/A intermolecular interactions. The results show that SMA LA17 with low A/A interactions exhibits inferior performance around 12%, owing to its strong D/A interaction with donor PM6, which shapes too miscible morphology and increases charge recombination. Instead, LA16 with strong A/A interactions and moderate D/A interactions delivers improved bulk‐heterojunction (BHJ) networks, and therefore, enhances charge transport and diminishes geminate or trap‐assisted charge recombination. Consequently, PM6:LA16 records the competitive efficiency of up to 13.74% among the three systems. Therefore, this study deepens the synergistic or balancing effect of the D/A and A/A interactions on BHJ blends for efficient organic solar cells. [ABSTRACT FROM AUTHOR]

Triplet excitons have both longer lifetimes and diffusion lengths than singlet excitons due to the nature of triplet excitons, which is expected to increase the photocurrent and further improve the performance of organic solar cells (OSCs). However, the working mechanism of triplet excitons in OSCs is not clearly clarified. Therefore, it is urgent to develop new triplet acceptors for in‐depth understanding. Herein, a series of acceptors (BTn‐4Cl) are synthesized by fine‐tuning of the side‐chain branch positions. The generation of triplet excitons of BTn‐4Cl is confirmed by the time‐resolved photoluminescence (TRPL) spectra, magnetophotocurrent (MPC) experiment, and electron paramagnetic resonance (EPR) spectra. The effects of side‐chain engineering on the optoelectronic properties, packing behaviors, energy losses, charge transport properties, spin lifetimes of triplet polarons, and blend film morphologies are systematically studied. These results show that D18:BT3‐4Cl‐based OSCs possess the best power conversion efficiency (PCE) of 17.31% due to lower energy losses, less recombination losses, more balanced charge carrier mobilities, longer spin–lattice (T1) relaxation time, and more favorable morphology. This work enhances the understanding of the structure–property relationship for high‐performance triplet acceptors. [ABSTRACT FROM AUTHOR]

The design of polymer acceptors plays an essential role in the performance of all‐polymer solar cells. Recently, the strategy of polymerized small molecules has achieved great success, but most polymers are synthesized from the mixed monomers, which seriously affects batch‐to‐batch reproducibility. Here, a method to separate γ‐Br‐IC or δ‐Br‐IC in gram scale and apply the strategy of monomer configurational control in which two isomeric polymeric acceptors (PBTIC‐γ‐2F2T and PBTIC‐δ‐2F2T) are produced is reported. As a comparison, PBTIC‐m‐2F2T from the mixed monomers is also synthesized. The γ‐position based polymer (PBTIC‐γ‐2F2T) shows good solubility and achieves the best power conversion efficiency of 14.34% with a high open‐circuit voltage of 0.95 V when blended with PM6, which is among the highest values recorded to date, while the δ‐position based isomer (PBTIC‐δ‐2F2T) is insoluble and cannot be processed after parallel polymerization. The mixed‐isomers based polymer, PBTIC‐m‐2F2T, shows better processing capability but has a low efficiency of 3.26%. Further investigation shows that precise control of configuration helps to improve the regularity of the polymer chain and reduce the π–π stacking distance. These results demonstrate that the configurational control affords a promising strategy to achieve high‐performance polymer acceptors. [ABSTRACT FROM AUTHOR]

Anode modification is vital for improving device performance of organic solar cells (OSCs). PEDOT:PSS is the most widely applied hole transport layer (HTL) in OSCs. In this work, three kinds of modified HTLs, namely PEDOT:PSS‐PA, PEDOT:PSS‐TA, and PEDOT:PSS‐DA are readily prepared via simple doping of phenylethylamine derivatives into commercially available Al 4083, by modulating the number of hydroxyl groups on the adulterant molecules. All of them exhibit enhanced work functions (WFs) and conductivities. Matching with PM6:Y6 composed active layers, PEDOT:PSS‐TA based devices achieves the highest performance with a power conversion efficiency (PCE) of 17.10%, while the PM6:ITC‐2Cl system demonstrates a highest PCE of 14.17% in devices with PEDOT:PSS‐DA, and the optimal PCE of PM6:PIDTC‐T based OSCs is equal to 9.55% while the HTL is PEDOT:PSS‐PA. Further investigations reveal that the different adulterants formed various amount of hydrogen bonds in HTLs, inducing dissimilar interfacial morphology and mobility, and thus unidentical degrees of change in recombination. Afterwards, the doping strategy is extended to a newly proposed high‐performance system PM6:PY‐IT, and successfully drags its efficiency from 14.78% to 15.62%, another world‐class breakthrough for all‐polymer solar cells. In summary, this study not only achieves a series of OSCs with improved PCEs, but also delivers a deep understanding of PEDOT:PSS improvement. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: The molecular weight of polymers plays a major role in their aggregation and miscibility in active layer, which eventually dominate the energy loss and device performance. A series of chlorine‐substituted PBD‐Cl polymers with controlled molecular weight have been synthesized as templates to discern a relationship between molecular weight and the optical properties, energy levels, morphologies, energy loss and photovoltaic performance. Although it has similar optical and electrochemical properties, when blended with acceptor N3, the low molecular weight polymer PBD‐ClL gives the biggest energy loss value, and a PCE of 12.06%. PBD‐ClH shows a moderate energy loss, but displays the lowest PCE of 9.00% as a result of excessive aggregation. PBD‐ClM with a medium molecular weight gives the smallest energy loss and achieves a PCE of 17.17%, which is among one of the highest values recorded to date for the Cl‐substituted polymer solar cells. Moreover, the molecular weight mainly affects the nonradiative energy loss (ΔE3), PBD‐ClM also shows the smallest value of 0.252 eV among three polymer donors. These results show the effect of controlling the molecular weight to achieve a small energy loss and provide guidelines which can lead to an understanding of the real photovoltaic performance of new materials. [ABSTRACT FROM AUTHOR]

The position of a chlorine atom in a charge carrier of polymer solar cells (PSCs) is important to boost their photovoltaic performance. Herein, two chlorinated D‐A conjugated polymers PBBD‐Cl‐α and PBBD‐Cl‐β are synthesized based on two new building blocks (TTO‐Cl‐α and TTO‐Cl‐β) respectively by introducing the chlorine atom into α or β position of the upper thiophene of the highly electron‐deficient benzo[1,2‐b:4,5‐c′]dithiophene‐4,8‐dione moiety. Single‐crystal analysis demonstrates that the chlorine‐free TTO shows a π‐π stacking distance (dπ‐π) of 3.55 Å. When H atom at the α position of thiophene of TTO is replaced by Cl, both π‐π stacking distance (dπ‐π = 3.48 Å) and Cl···S distance (dCl‐S = 4.4 Å) are simultaneously reduced for TTO‐Cl‐α compared with TTO. TTO‐Cl‐β then showed the Cl···S non‐covalent interaction can further shorten the intermolecular π‐π stacking separation to 3.23 Å, much smaller than that of TTO‐Cl‐α and TTO. After blending with BTP‐eC9, PBBD‐Cl‐β:BTP‐eC9‐based PSCs achieved an outstanding power conversion efficiency (PCE) of 16.20%, much higher than PBBD:BTP‐eC9 (10.06%) and PBBD‐Cl‐α:BTP‐eC9 (13.35%) based devices. These results provide an effective strategy for design and synthesis of highly efficient donor polymers by precise positioning of the chlorine substitution. [ABSTRACT FROM AUTHOR]

Ternary organic solar cells (TOSCs) offer a facile and efficient approach to increase the power conversion efficiencies (PCEs). However, the critical roles that guest components play in complicated ternary systems remain poorly understood. Herein, two acceptors named LA1 and LA9 with differing crystallinity are investigated. The overly crystalline LA9 induces large self‐aggregates in PM6:LA9 binary system, resulting in a lower PCE (13.12%) compared to PM6:LA1 device (13.89%). Encouragingly, both acceptors are verified as efficient guest candidates into the host binary PM6:NCBDT‐4Cl (PCE = 13.48%) and afford markedly improved PCEs up to 15.39% and 15.75% in LA1 and LA9 ternary devices, respectively. Interestingly, the higher crystallinity LA9 reveals smaller interaction energies with both the host acceptor and donor PM6. Compared to LA1, the appropriate mutual interactions in the LA9 ternary system not only induces the orderly crystallinity of PM6 but also better compatibility with the host acceptor, generating further optimized molecular orientations and ternary morphology. Therefore, enhanced charge transport and minimized recombination loss are detected in LA9 ternary devices, affording the most competitive performance among Y6‐sbsent TOSCs. This work suggests that complicated intermolecular interactions should be seriously considered when fabricating state‐of‐the‐art multiple components OSCs. [ABSTRACT FROM AUTHOR]

The concept of bromination for organic solar cells has received little attention. However, the electron withdrawing ability and noncovalent interactions of bromine are similar to those of fluorine and chlorine atoms. A tetra‐brominated non‐fullerene acceptor, designated as BTIC‐4Br, has been recently developed by introducing bromine atoms onto the end‐capping group of 2‐(3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene) malononitrile and displayed a high power conversion efficiency (PCE) of 12%. To further improve its photovoltaic performance, the acceptor is optimized either by introducing a longer alkyl chain to the core or by modulating the numbers of bromine substituents. After changing each end‐group to a single bromine, the BTIC‐2Br‐m‐based devices exhibit an outstanding PCE of 16.11% with an elevated open‐circuit voltage of Voc = 0.88 V, one of the highest PCEs reported among brominated non‐fullerene acceptors. This significant improvement can be attributed to the higher light harvesting efficiency, optimized morphology, and higher exciton quenching efficiencies of the di‐brominated acceptor. These results demonstrate that the substitution of bromine onto the terminal group of non‐fullerene acceptors results in high‐efficiency organic semiconductors, and promotes the use of the halogen‐substituted strategy for polymer solar cell applications. [ABSTRACT FROM AUTHOR]

Ternary strategy is a promising approach to broaden the photoresponse of polymer solar cells (PSCs) by adopting combinatory photoactive blends. However, it could lead to a more complicated situation in manipulating the bulk morphology. Achieving an ideal morphology that enhances the charge transport and light absorption simultaneously is an essential avenue to promote the device performance. Herein, two polymers with different lengths of side groups (P1 is based on phenyl side group and P2 is based on biphenyl side group) are adopted in the dual‐acceptor ternary systems to evaluate the relationship between conjugated side group and crystalline behavior in the ternary system. The P1 ternary system delivers a greatly improved power conversion efficiency (PCE) of 13.06%, which could be attributed to the intense and broad photoresponse and improved charge transport originating from the improved crystallinity. Inversely, the P2 ternary device only exhibits a poor PCE of 8.97%, where the decreased device performance could mainly be ascribed to the disturbed molecular stacking of the components originating from the overlong conjugated side group. The results demonstrate a conjugated side group could greatly determine the device performance by tuning the crystallinity of components in ternary systems. [ABSTRACT FROM AUTHOR]

By introduction of four hydroxy (HO) groups into the two perylene bisimide (PBI) bay areas, new HO‐PBI ligands were obtained which upon deprotonation can complex ZnII ions and photosensitize semiconductive zinc oxide thin films. Such coordination is beneficial for dispersing PBI photosensitizer molecules evenly into metal oxide films to fabricate organic–inorganic hybrid interlayers for organic solar cells. Supported by the photoconductive effect of the ZnO:HO‐PBI hybrid interlayers, improved electron collection and transportation is achieved in fullerene and non‐fullerene polymer solar cell devices, leading to remarkable power conversion efficiencies of up to 15.95 % for a non‐fullerene based organic solar cell. [ABSTRACT FROM AUTHOR]

Abstract: Three low‐bandgap nonfullerene acceptors (NFAs) IDTO‐T‐4F, IDTO‐Se‐4F, and IDTO‐TT‐4F with extended conjugation length are designed and synthesized. Various π‐spacers, thiophene, selenophene, and thieno[3,2‐b]thiophene are incorporated to extend the conjugated length and enhance the backbone planarity via noncovalent O···S or O···Se interactions. These NFAs exhibit strong light absorption in the range of 600–900 nm with narrow bandgaps between 1.38 and 1.45 eV. By blending with a wide‐bandgap donor material PBDB‐T, organic solar cells (OSCs) based on these NFAs all yield high efficiency over 10% with low energy losses ranging from 0.52 to 0.59 eV. Importantly, as a result of relatively high lowest unoccupied molecular orbital level, large hole and electron mobility in blend film, and low charge carrier recombination loss, optimized devices based on IDTO‐T‐4F exhibit a large open‐circuit voltage of 0.864 V, a high short‐circuit current density of 20.12 mA cm−2, and a notable fill factor of 72.7%, leading to an impressive efficiency of 12.62%, which represents the best performance for NFA OSCs using noncovalent interactions in acceptor molecule design. The results indicate that optimizing the conjugation length and backbone planarity via intramolecular noncovalent O···S or O···Se interactions is a useful strategy for NFA materials invention toward high‐performance solar cells. [ABSTRACT FROM AUTHOR]

Developing efficient organic solar cells (OSCs) with relatively thick active layer compatible with the roll to roll large area printing process is an inevitable requirement for the commercialization of this field. However, typical laboratory OSCs generally exhibit active layers with optimized thickness around 100 nm and very low thickness tolerance, which cannot be suitable for roll to roll process. In this work, high performance of thick‐film organic solar cells employing a nonfullerene acceptor F–2Cl and a polymer donor PM6 is demonstrated. High power conversion efficiencies (PCEs) of 13.80% in the inverted structure device and 12.83% in the conventional structure device are achieved under optimized conditions. PCE of 9.03% is obtained for the inverted device with active layer thickness of 500 nm. It is worth noting that the conventional structure device still maintains the PCE of over 10% when the film thickness of the active layer is 600 nm, which is the highest value for the NF‐OSCs with such a large active layer thickness. It is found that the performance difference between the thick active layer films based conventional and inverted devices is attributed to their different vertical phase separation in the active layers. [ABSTRACT FROM AUTHOR]

Ternary polymer solar cells (PSCs) are one of the most promising device architectures that maintains the simplicity of single‐junction devices and provides an important platform to better tailor the multiple performance parameters of PSCs. Herein, a ternary PSC system is reported employing a wide bandgap polymeric donor (PBTA‐PS) and two small molecular nonfullerene acceptors (labeled as LA1 and 6TIC). LA1 and 6TIC keep not only well‐matched absorption profiles but also the rational crystallization properties. As a result, the optimal ternary PSC delivers a state of the art power conversion efficiency (PCE) of 14.24%, over 40% higher than the two binary devices, resulting from the prominently increased short‐circuit current density (Jsc) of 22.33 mA cm−2, moderate open‐circuit voltage (Voc) of 0.84 V, and a superior fill factor approaching 76%. Notably, the outstanding PCE of the ternary PSC ranks one of the best among the reported ternary solar cells. The greatly improved performance of ternary PSCs mainly derives from combining the complementary properties such as absorption and crystallinity. This work highlights the great importance of the rational design of matched acceptors toward highly efficient ternary PSCs. [ABSTRACT FROM AUTHOR]

It is a great challenge to simultaneously improve the two tangled parameters, open circuit voltage (Voc) and short circuit current density (Jsc) for organic solar cells (OSCs). Herein, such a challenge is addressed by a synergistic approach using fine‐tuning molecular backbone and morphology control simultaneously by a simple yet effective side chain modulation on the backbone of an acceptor–donor–acceptor (A–D–A)‐type acceptor. With this, two terthieno[3,2‐b]thiophene (3TT) based A–D–A‐type acceptors, 3TT‐OCIC with backbone modulation and 3TT‐CIC without such modification, are designed and synthesized. Compared with the controlled molecule 3TT‐CIC, 3TT‐OCIC shows power conversion efficiency (PCE) of 13.13% with improved Voc of 0.69 V and Jsc of 27.58 mA cm−2, corresponding to PCE of 12.15% with Voc of 0.65 V and Jsc of 27.04 mA cm−2 for 3TT‐CIC–based device. Furthermore, with effective near infrared absorption, 3TT‐OCIC is used as the rear subcell acceptor in a tandem device and gave an excellent PCE of 15.72%. [ABSTRACT FROM AUTHOR]

A wide‐bandgap conjugated polymer, PNQx‐2F2T, based on a ring‐fused unit of quinoxalino[6,5‐f  ]quinoxaline (NQx), is synthesized for use as electron donor in polymer solar cells (PSCs). The polymer shows intense light absorption in the range from 300 to 740 nm and favorable energy levels of frontier molecular orbitals. The polymer has afforded decent device performance when blended with either fullerene‐based acceptor [6,6]‐phenyl‐C71‐butylric acid methyl ester ([70]PCBM) or non‐fullerene acceptor 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone‐methyl))‐5,5,11,11‐tetrakis(4‐n‐hexylphenyl)‐dithieno[2,3‐d: 2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (IT‐M). The highest PCEs of 7.9% and 7.5% have been achieved for [70]PCBM or IT‐M based PSCs, respectively. Moreover, the influence of molecular weight of PNQx‐2F2T on solar cell performance has been investigated. It is found that fullerene‐based devices prefer higher polymer molecular weight, while non‐fullerene devices are not susceptible to the molecular weight of PNQx‐2F2T. The device results are extensively explained by electrical and morphological characterizations. This work not only evidences the potential of NQx for constructing high‐performance photovoltaic polymers but also demonstrates a useful structure–performance relationship for efficiency enhancement of non‐fullerene PSCs via the development of new conjugated polymers. [ABSTRACT FROM AUTHOR]

A novel phenyl substituted benzo(1,2‐b:4,5‐b')dithiophene (BDT) derivative containing both fluorine and sulfur atoms is designed and synthesized. Furthermore, a wide bandgap polymer PBTA‐PSF based on the derivative shows a low highest occupied molecular orbital energy level and slightly reduces the donor materials' optical bandgap, which has a complementary absorption with a narrow‐bandgap n‐type small molecule ITIC. As a result, a power conversion efficiency of 13.91% is achieved with a high open‐circuit voltage of 1.01 V, and a large short‐circuit current density of 18.51 mA cm−2. The result demonstrates that PBTA‐PSF is a promising candidate for high‐performance donor and phenyl‐containing BDT derivatives and has potential in the design of high‐performance polymers for organic photovoltaics. A novel phenyl substituted benzo(1,2‐b:4,5‐b')dithiophene (BDT) derivative containing both fluorine and sulfur atoms is designed and synthesized. A power conversion efficiency of 13.91% is achieved with a high open‐circuit voltage of 1.01 V, and a large short‐circuit current density of 18.51 mA cm−2. The result demonstrates that PBTA‐PSF is a promising candidate for high‐performance donor polymers. [ABSTRACT FROM AUTHOR]

Two new nonfullerene small molecule acceptors (NF‐SMAs) AT‐NC and AT‐4Cl based on heptacyclic anthracene(cyclopentadithiophene) (AT) core and different electron‐withdrawing end groups are designed and synthesized. Although the two new acceptor molecules use two different end groups, naphthyl‐fused indanone (NINCN) and chlorinated INCN (INCN‐2Cl) demonstrate similar light absorption. AT‐4Cl with chlorinated INCN as end groups are shifted significantly due to the strong electron‐withdrawing ability of chlorine atoms. Thus, desirable Voc and photovoltaic performance are expected to be achieved when polymer PBDB‐T is used as the electron donor with AT‐NC as the acceptor, and fluorinated analog PBDB‐TF with down‐shifted energy levels is selected to blend with AT‐4Cl. Consequently, the device based on PBDB‐TF:AT‐4Cl yields a high power conversion efficiency of 13.27% with a slightly lower Voc of 0.901 V, significantly enhanced Jsc of 19.52 mA cm−2 and fill factor of 75.5% relative to the values based on PBDB‐T:AT‐NC. These results demonstrate that the use of a new electron‐rich AT core, together with energy levels modulations by end‐group optimizations enabling the match with polymer donors, is a successful strategy to construct high‐performance NF‐SMAs. By using the new electron‐rich heptacyclic anthracene(cyclopentadithiophene) (AT) core, together with energy level modulations by end‐group optimizations enabling the match with polymer donors, two new nonfullerene small molecule acceptors AT‐NC and AT‐4Cl are synthesized. With both halogenated donor and acceptor, the organic photovoltaics device based on AT‐4Cl achieves a high power conversion efficiency of 13.27% with simultaneously improved Jsc and fill factor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkyl chain engineering is used in non-fused ring acceptor to tune the optoelectronic properties of materials. • The effect of alkyl side chain length on physicochemical and optoelectronic properties are systematically investigated. • A power conversion efficiency of 12.53% with low energy loss of 0.51 eV is achieved. • A relatively low energetic disorder with Urbach energy of 24.01 meV is obtained. Non-fused ring electron acceptors are attractive for organic solar cell (OSC) due to synthetic simplicity and availability of diverse building blocks. However, it is challenging to afford both high-performance and low-energy loss (E loss) OSC based on the non-fused ring electron acceptors. Herein, two simple electron acceptors, BDC-4F-C6 and BDC-4F-C8 with non-fused backbones are designed and synthesized by comprising a 5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione core, doubly endcapped by fluorinated 1,1-dicyanomethylene-3-indanone terminals through 4H-cyclopenta[1,2-b:5,4-b′]dithiophene bridge. The effects of bridge alkyl side chain length on physicochemical properties and on optoelectronic properties are systematically investigated. Compared with the BDC-4F-C6, BDC-4F-C8 shows a blue-shifted absorption and an elevated LUMO level, which is beneficial for boosting V oc. As a result, a decent power conversion efficiency of 12.53% with a remarkable low E loss of 0.51 eV has been achieved for BDC-4F-C8-based OSCs. It is worth pointing out that E loss of 0.51 eV is the lowest ever reported among highly efficient OSCs based on non-fused ring electron acceptors. Our work demonstrates the effectiveness of side chain engineering of non-fused ring electron acceptors for achieving higher PCE and lower E loss , holding a bright future on the further improvement of the PCE for high-performance OSCs. [ABSTRACT FROM AUTHOR]

• A PCE over the 13% for ternary PSCs based on ternary polymer donor was achieved. • Morphology studies confirmed that ternaty PSC brought most appropriate phase separation. • A classical ternary strategy could significantly improve charge extraction. The third component played an increasingly significant role in polymer solar cells (PSCs), especially for the morphological impact. Here, we use a ternary polymer donor (TBFCl50-BDD) and organic small molecule acceptor (BTP-4F) as the main material and introduce a third component (PC 71 BM) to enhance the morphology of the photoactive layer and result in improved device performance. The TBFCl50-BDD:BTP-4F based PSCs only exhibited an efficiency of 10.58%, while The power conversion efficiency of ternary device (TBFCl50-BDD:BTP-4F:PC 71 BM) reached 13.15%. Importantly, the introduction of PC 71 BM can not only improve the morphology of the active layer and promote more efficient exciton transport, but also influence the molecular arrangement for better crystallization performance. This work offers an effective method for optimization of the morphology to enhance the properties of PSCs. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: The molecular weight of polymers plays a major role in their aggregation and miscibility in active layer, which eventually dominate the energy loss and device performance. A series of chlorine‐substituted PBD‐Cl polymers with controlled molecular weight have been synthesized as templates to discern a relationship between molecular weight and the optical properties, energy levels, morphologies, energy loss and photovoltaic performance. Although it has similar optical and electrochemical properties, when blended with acceptor N3, the low molecular weight polymer PBD‐ClL gives the biggest energy loss value, and a PCE of 12.06%. PBD‐ClH shows a moderate energy loss, but displays the lowest PCE of 9.00% as a result of excessive aggregation. PBD‐ClM with a medium molecular weight gives the smallest energy loss and achieves a PCE of 17.17%, which is among one of the highest values recorded to date for the Cl‐substituted polymer solar cells. Moreover, the molecular weight mainly affects the nonradiative energy loss (ΔE3), PBD‐ClM also shows the smallest value of 0.252 eV among three polymer donors. These results show the effect of controlling the molecular weight to achieve a small energy loss and provide guidelines which can lead to an understanding of the real photovoltaic performance of new materials. [ABSTRACT FROM AUTHOR]

The high energy loss (E loss) in organic solar cells (OSCs) is being the one of major problem, which limit the power conversion efficiency (PCE) of OSCs. In this work, we designed and synthesized three perylene diimide (PDI)-based Acceptor'-Donor-Acceptor-Donor- Acceptor' (A′-DAD-A′) small molecules namely anti -PDFC-Cx (C8, C10, and C12) by changing the length of linear chains on IDT cores to investigate how the length of linear side chain affects E loss and the power conversion efficiencies (PCEs) of OSCs. The optical energy bandgap and stacking mode for three anti -PDFC-Cx (C8, C10, and C12) remain the same, which were not influenced by the different lengths of side chains. Increasing the length of side chains on IDT cores from C8 to C10 and C12 would improve the PCE of PM6: anti -PDFC-Cx based devices from 11.52% to 12.43% and 12.27%, particularly the V oc increasing from 0.98 V of anti -PDFC-C8 and 1.00 V of anti -PDFC-C10 to 1.02 V of anti -PDFC-C12. E loss analysis indicated the value of E loss reduced as the length increases from C8, to C12. These results demonstate linear side chain engineer is an effective method to reduce E loss and realize high PCE on the bases of not modulating the stacking mode of acceptor. [Display omitted] • Three perylene diimide (PDI)-based A'-DAD-A' small molecules namely anti -PDFC-Cx (C8, C10, and C12) were synthesized. • The optical energy bandgap and stacking mode for three small molecules were not influenced by the different lengths of side chains. • Increasing the length of side chains would improve the V oc of PM6: anti -PDFC-Cx based devices from 0.98 V, 1.00 V to 1.02 V. [ABSTRACT FROM AUTHOR]

• The V 2 O 5 nanoparticles can fill the pinholes in PEDOT:PSS. • The hole transport layer of V 2 O 5 :PEDOT:PSS has high conductivity and hydrophobicity. • The crystallizability of the active layer is improved by adjusting the interface. • The PCE over 9.4% and FF over 70% can be achieved in OSCs with composite HTL. The fill factor (FF) as an important photovoltaic parameter is related to the property of transport layers and active layers for organic solar cells (OSCs). Herein, we propose a simple method to improve FF by using inorganic-organic composite hole transport layer (HTL) in OSCs. Through incorporating inorganic metal oxide, vanadium pentoxide (V 2 O 5) nanoparticles into PEDOT:PSS, the morphology and conductivity of the composite HTL are improved, due to V 2 O 5 nanoparticles can fill the pinholes in PEDOT:PSS and expose more PEDOT chains to the surface core–shell structure. The PTB7-Th:PC 71 BM-based OSCs with different HTLs were prepared. The power conversion efficiency and FF of the OSCs for the composite HTL can be greatly improved compared with the traditional HTL, which can reach up to 9.44% and 70.14%, respectively. The results of water contact angle and grazing incidence wide-angle X-ray scattering show that the hydrophobicity of the composite HTL is improved, which can not only improve the physical contact but also greatly affect the subsequent active layer formation, thus increasing the crystallinity of PTB7-Th:PC 71 BM. These results demonstrate that V 2 O 5 :PEDOT:PSS has good application prospects as a HTL to realize high-efficient OSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorinated benzylammonium iodide is employed as bulky cation to fabricate the quasi-2D perovskite solar cell. • The fabrication of quasi-2D perovskite is carried out in humidity-controlled ambient air. • The quasi-2D perovskite films exhibit vertical orientation with less grain boundaries and almost no pinhole. • A remarkable PCE of 20.12% with a relatively high open-voltage circuit of 1.223 V was achieved in champion device. Quasi-2D perovskite solar cells (PSCs) have attracted extensive attention recently because of their superior stability to moisture, but their power conversion efficiency (PCE) still lags behind that of 3D counterparts. So, it is urgent to explore more stable and highly efficient quasi-2D PSCs. Herein, we employed fluorinated benzylammonium iodide as bulky cation to fabricate the quasi-2D PSCs. With the bulky action, quasi-2D perovskite films exhibit vertical orientation with less grain boundaries and almost no pinhole, all of which can suppress non-radiative recombination and improve the charge collection in photovoltaic devices. As a result, a remarkable PCE of 20.12% with a relatively high open-voltage circuit of 1.223 V was achieved in champion device. More interestingly, the fabrication of our quasi-2D perovskite was carried out in a humidity-controlled ambient air, which demonstrates much more advantage comparing with other quasi-2D perovskites as the literatures reported so far, in which the preparation of low-dimensional perovskites usually requires a glove box filled with an inert gas. This work shed light on the development of high-quality quasi-2D perovskite film fabricated in humidity-controlled ambient air by simple and easy process, which is appealing for the future industrialization of PSCs with low-cost. [ABSTRACT FROM AUTHOR]