Xiaowei Zhan

Xiaowei Zhan
Peking University | PKU · College of Engineering

PhD

About

380
Publications
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40,849
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Publications

Publications (380)
Article
Fused-ring electron acceptors (FREAs) have a donor–acceptor–donor structure comprising an electron-donating fused-ring core, electron-accepting end groups, π-bridges and side chains. FREAs possess beneficial features, such as feasibility to tailor their structures, high property tunability, strong visible and near-infrared light absorption and exce...
Article
We synthesize and compare four near-infrared absorbing fused-ring electron acceptors named as nTTIC (n=2, 3, 4, and 5), based on different number of thieno[3,2-b]thiophene (TT) unit as the electron-donating core. With increasing the TT unit, absorption spectrum of the TTIC series red shifts, and the highest occupied molecular orbital (HOMO) upshift...
Article
Full-text available
Organic photovoltaics (OPVs) promise cheap and flexible solar energy. Whereas light generates free charges in silicon photovoltaics, excitons are normally formed in organic semiconductors due to their low dielectric constants, and require molecular heterojunctions to split into charges. Recent record efficiency OPVs utilise the small molecule, Y6,...
Article
The design of photosensitizers with multimodal antitumor activity and the construction of nanocarriers with specific targeting are two magic weapons to achieve highly efficient tumor phototherapy. Here we developed an A-D-A fused-ring conjugated small molecule photosensitizer DPIC and proposed a new strategy of constructing phototherapy agents, nam...
Article
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Two new fused‐ring electron acceptor (FREA) isomers with nonlinear and linear molecular conformation, m‐BAIDIC and p‐BAIDIC, are designed and synthesized. Despite the similar light absorption range and energy levels, the two isomers exhibit distinct electron reorganization energies and molecular packing motifs, which are directly related to the mol...
Article
Full-text available
The tuning of vertical morphology is critical and challenging for organic solar cells (OSCs). In this work, a high open‐circuit voltage (VOC) binary D18‐Cl/L8‐BO system is attained while maintaining the high short‐circuit current (JSC) and fill factor (FF) by employing 1,4‐diiodobenzene (DIB), a volatile solid additive. It is suggested that DIB can...
Article
D‐A conjugated polymers P1 and P2 are synthesized by copolymerizing bisthiophene‐fused diketopyrrolopyrrole (4,11‐bis(2‐decyltetradecyl)‐7H,14H‐thieno[3',2':7,8]‐indolizino[2,1‐a]thieno[3,2‐g]indolizine‐7,14‐dione, BTI) with terthiophene and thiophene‐benzothiadiazole‐thiophene, respectively. Molecular packing is characterized by X‐ray diffraction....
Article
Organic solar cells (OSCs) based on a bulk heterojunction structure exhibit inherent advantages, such as low cost, light weight, mechanical flexibility, and easy processing, and they are emerging as a potential renewable energy technology. However, most studies are focused on lab-scale, small-area (<1 cm2) devices. Large-area (>1 cm2) OSCs still ex...
Article
We used dual nonfullerene acceptors Y6:FINIC with 3D charge transport features and polymer donor PM6 to fabricate sequential-process heterojunction (SHJ) and bulk heterojunction (BHJ) organic solar cells (OSCs). FINIC has...
Article
Two isomeric fused-ring electron acceptors F7TC-1 and F7TC-2 with different molecular symmetry are designed and synthesized, and the effect of molecular symmetry is studied. All side chains are located on the same side of fused-ring core in axisymmetric F7TC-1, while those are evenly located on both sides of fused-ring core in centrosymmetric F7TC-...
Article
We present the first report incorporating strongly electron-donating moiety pyrrolo[3,2-b]pyrrole into fused-ring electron acceptors, and design and synthesize two narrow-bandgap nonfullerene acceptor isomers PPIC1 and PPIC2. These two molecules bear the same electron-withdrawing terminal groups and isomeric eight-fused-ring cores. The two compound...
Article
Full-text available
The bulk morphology of the active layer of organic solar cells (OSCs) is known to be crucial to the device performance. The thin film device structure breaks the symmetry into the in-plane direction and out-of-plane direction with respect to the substrate, leading to an intrinsic anisotropy in the bulk morphology. However, the characterization of o...
Article
Device stability becomes one of the most crucial issues for the commercialization of organic solar cells (OSCs) after high power conversion efficiencies have been achieved. Besides the intrinsic stability of photoactive materials, the chemical/catalytic reaction between interfacial materials and photoactive materials is another critical factor that...
Article
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A novel blend thin film, (N,N-dimethyl-ammonium N-oxide)propyl perylene diimide mixed with polyethylenimine ethoxylated (PDINO:PEIE), is provided as cathode modifying layer in organic solar cells (OSCs). Compared to PDINO, PDINO:PEIE shows increased electron conduction, due to the weak n-doping of PDINO by the amino groups of PEIE, improving the ba...
Article
Organic photodetectors (OPDs), which usually work as photodiodes, photoconductors, or phototransistors, have emerged as candidates for next-generation light sensing. However, low response speed caused by low carrier mobility and resistance-capacitance (RC) time constant, severely hinders the commercialization of OPDs. Herein, the authors demonstrat...
Article
Two intermediates (dimethyl 3,7‐dibromonaphthalene‐2,6‐dicarboxylate and dimethyl 1,5‐dibromonaphthalene‐2,6‐dicarboxylate) were synthesized to realize the isomerization of naphthalene‐based decacyclic fused‐ring electron acceptors FTIC1 and FTIC2. The linear‐shaped FTIC1 and nonlinear‐shaped FTIC2 share the same terminal groups and side chains but...
Preprint
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Organic photovoltaic cells promise cheap, flexible and scalable solar energy. Whereas light directly generates free charges in silicon photovoltaic cells, bound electron and hole pairs known as excitons are understood to be the primary excitations in organic semiconductors due to their low dielectric constants. These excitons must then be split apa...
Article
Full-text available
Poly(3-hexylthiophene) (P3HT) is regarded as one of the most promising polymer donors for organic solar cells (OSCs) owing to its own merits of low-cost and controllable synthesis, large-area and roll-to-roll printing device fabrication. However, the mutual restriction and imbalance of the open-circuit voltage (VOC) and short-circuit current densit...
Article
Full-text available
A new fused‐ring electron acceptor FNIC3 with dynamics controlled aggregation behavior was synthesized. FNIC3 shows strong absorption in 600–900 nm, HOMO/LUMO energy levels of −5.59/−4.04 eV, and electron mobility of 1.2 × 10⁻³ cm² V⁻¹ s⁻¹. The aggregation of FNIC3 shows strong dependency on film formation time. Prolongation of film formation time...
Article
The development of organic photovoltaic (OPV) cells has long been guided by the idea that excitons – bound electron-hole pairs created by light absorption – diffuse only 5-10 nm. True for many materials, this constraint led to an inherently complex device architecture – the bulk heterojunction – that has obscured our understanding of device physics...
Article
Full-text available
Researchers are endeavoring to decode the fundamental reasons for the non-fullerene acceptor, Y6, to deliver high-performance organic solar cells. In this manuscript, we tackle this problem from the molecular packing...
Article
We designed and synthesized two isomers AOIC1 and AOIC2 by unidirectional extension of the same asymmetric precursor in different directions and separated by selectivity of Lewis-acid-mediated Friedel-Crafts reaction due to different steric hindrance of the side chains. AOIC1 and AOIC2 were compared with our reported AOIC to study the isomeric effe...
Article
ConspectusEmerging solar cells that convert clean and renewable solar energy to electricity, such as organic solar cells (OSCs) and perovskite solar cells (PSCs), have attracted increasing attention owing to some merits such as facile fabrication, low cost, flexibility, and short energy payback time. The power conversion efficiencies (PCEs) of OSCs...
Article
We designed and synthesized a series of fused-ring electron acceptors (FREAs) based on naphthalene-fused octacyclic cores end-capped by 3-(1,1-dicyanomethylene)-5,6-difluoro-1- indanone (NOICs) using a bottom-up approach. The NOIC series shares the same end groups and side chains, as well as similar fused-ring cores. The butterfly effects, arising...
Article
The bulk-heterojunction morphology of organic solar cells is well recognized to be critical to the device performance and has received extensive research efforts in developing viable morphology tuning strategies. In this work, we present a morphology tuning approach for the molecular packing orientation, that is, through the ternary mixing of a don...
Article
Non-fullerene acceptors (NFAs) are highly promising materials for organic photovoltaics (OPVs). Exciton diffusion in NFAs is crucial to their photovoltaic performance, but is not yet well understood. Here we systematically examine exciton diffusion in a fused-ring electron acceptor (IDIC) based on a first-principles framework. We discover that low-...
Article
The ternary strategy has been widely used in high-efficiency organic solar cells (OSCs). Herein, we successfully incorporated a mid-band-gap star-shaped acceptor, FBTIC, as the third component into the PM6/Y6 binary blend film, which not only achieved a panchromatic absorption but also significantly improved the open-circuit voltage (V OC) of the d...
Article
Full-text available
At present, most of the top-performing organic solar cells (OSCs) are processed with high boiling point solvent additives, which usually have a negative effect on the device stability. To overcome this conundrum, we herein introduce a commercially available organic transition metal compound, ferrocene, as a highly volatile solid additive in OSCs. T...
Article
Full-text available
Thanks to the nature of molecular orbitals, the absorption spectra of organic semiconductors are not continuous like those in traditional inorganic semiconductors, which offers a unique application of organic photovoltaics (OPVs): semitransparent OPVs. Recently, the exciting progress of materials design has promoted the development of semitranspare...
Article
Full-text available
In tandem organic photovoltaics, the front subcell is based on large‐bandgap materials, whereas the case of the rear subcell is more complicated. The rear subcell is generally composed of a narrow‐bandgap acceptor for infrared absorption but a large‐bandgap donor to realize a high open‐circuit voltage. Unfortunately, most of the ultraviolet–visible...
Article
The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was...
Article
Four fused‐ring electron acceptors consisting of the same indacenobis(dithieno[3,2‐b ;2′,3′‐d ]thiophene) core and 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ ylidene)malononitrile end‐groups without or with fluorination on side‐chains and/or end‐groups are compared to probe the impacts of fluorination position on molecular packing, optical, electronic, and photo...
Article
Full-text available
To take advantages of the intense absorption and fluorescence, high charge mobility, and high dielectric constant of CsPbI3 perovskite quantum dots (PQDs), PQD hybrid nonfullerene organic solar cells (OSCs) are fabricated. Addition of PQDs leads to simultaneous enhancement of open‐circuit voltage (V OC), short‐circuit current density (J SC), and fi...
Article
Three fused-ring electron acceptors (SIDIC, DIDIC and TIDIC) were designed and synthesized using single/double/triple bond linked indaceno[3,2-b]dithiophene dimers as electron-rich cores and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone as electron-deficient termini. These molecules exhibit strong absorption from 550 to 900 nm with large attenua...
Article
Full-text available
A new fluorinated electron acceptor (FINIC) based on 6,6,12,12‐tetrakis(3‐fluoro‐4‐hexylphenyl)‐indacenobis(dithieno[3,2‐b;2′,3′‐d]thiophene) as the electron‐donating central core and 5,6‐difluoro‐3‐(1,1‐dicyanomethylene)‐1‐indanone as the electron‐deficient end groups is rationally designed and synthesized. FINIC shows similar absorption profile i...
Article
Four fused-ring electron acceptors composed of the same naphtho[1,2-b:5,6-b']dithiophene-based core and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone end groups without or with hexyloxyl groups on core and/or phenyl side chains are compared to systematically study the effects of alkoxylation position on molecular packing, optical, electronic, an...
Article
Full-text available
The two-photon absorption (2PA) properties are investigated for two series of organic, π-conjugated, fused-ring, quadrupolar A-π-D-π-A chromophores of the type originally developed as non-fullerene acceptors for organic photovoltaics. These molecules are found to exhibit large nondegenerate two-photon absorption (ND2PA) cross-sections (ca. 6-27 × 1...
Article
Full-text available
In article number 1904196, Xiaowei Zhan, Jordi Martorell and co‐workers design a building‐integrated transparent photovoltaic window based on an optically tailored organic solar cell, where enhanced sunlight harvesting at large oblique angles is largely decoupled from visual transmission at normal incidence, setting a new performance standard in th...
Article
A new fused‐ring electron acceptor FOIC1 was designed and synthesized. FOIC1 exhibits intense absorption in the range of 600‐1000 nm, HOMO/LUMO energy levels of –5.39/–3.99 eV, and electron mobility of 1.8 × 10–3 cm² V–1 s–1. Organic solar cells based on sequentially processed heterojunction (SHJ) with unusual inverted structure were fabricated. Th...
Article
Three fused-ring electron acceptors (FXIC-1, FXIC-2 and FXIC-3) were designed and synthesized. This FXIC series has similar electron-rich central units and the same electron-poor termini. Due to the different steric structures of fluorene, bifluorenylidene and spirobifluorene, FXIC-1 is a one-dimensional (1D) crystal, while FXIC-2 and FXIC-3 are mu...
Article
Full-text available
In consideration of the unique advantages of new non‐fullerene acceptors and the tandem‐junction structure, organic photovoltaics (OPVs) based on them are very promising. Studies related to this emerging area began in 2016 with achieved power conversion efficiencies (PCEs) of 8–10%, which have now been boosted to 17%. In this essay, the constructio...
Article
To enhance photoresponse of common‐used perovskite materials in the near‐infrared (NIR) region, a fused‐ring electron acceptor (F8IC) with strong NIR absorption and high electron mobility was used to blend with a narrow‐bandgap polymer donor (PTB7‐Th) to construct organic bulk heterojunction (OBHJ), and this OBHJ was then integrated with the perovs...
Article
Highly sensitive solution-processed organic photodetectors (OPDs) with a broadband response ranging from visible to near infrared (NIR) and excellent overall device performance are demonstrated. The OPDs were fabricated from a blend consisting of a wide bandgap polymer donor and a newly developed fused octacylic small-molecule electron acceptor wit...
Article
For many years, it has been recognized that potential organic photovoltaic cells must be integrated into elements requiring high transparency. In most of such elements, sunlight is likely to be incident at large angles. Here it is demonstrated that light transmission can be largely decoupled from harvesting by optically tailoring an infrared shifte...
Article
The rapid development of organic solar cells (OSCs) based on non‐fullerene acceptors has achieved significant breakthroughs in power conversion efficiency (PCE) of spin coated devices. However, spin coating method in a protective atmosphere seems unsuitable for the practical printing of high‐performance solar panels. In addition, the use of highly...
Article
Selecting suitable outermost aromatic rings of the central cores is of particular importance for design of fused-ring electron acceptors (FREAs), because the direct electronic communication between the outermost aromatic rings and termini exerts a strong impact on the optoelectronic properties of FREAs. In most cases, the outermost rings of the FRE...
Article
Full-text available
Organic-inorganic hybrid perovskite (OIHP) photodetectors that simultaneously achieve an ultrafast response and high sensitivity in the near-infrared (NIR) region are prerequisites for expanding current monitoring, imaging, and optical communication capbilities. Herein, we demonstrate photodetectors constructed by OIHP and an organic bulk heterojun...
Article
As known, to balance the open-circuit voltage (VOC) and short-circuit current density (JSC) is one of the effective strategies to improve the photovoltaic performances of OSCs. In this work, a thiophene-fused benzotriazole (BTAZT) unit acts as a “π-bridge” to build an acceptor (A3) with A-π-D-π-A structure for OSCs. Compared with a thiophene-fused...
Article
In semiconductor organic thin films, molecular crystallinity simultaneously influences the optical (light transmission) and electronic (transport energy level) properties. In this work, two isomeric acceptors with different crystallization capabilities in combination with different solvent additives are utilized to broadly tune the film-depth-depen...
Article
Suppressing trap states and localized electronic states in the forbidden gap of semiconductors as either active layers or contacts, is critical to the enhancement of optoelectronic device performance, such as solar cell, ultra-fast photodetectors, field-effect transistors as well as other optoelectronic applications. In this study, we demonstrate L...
Article
The unidirectional extension of a smaller fused-ring system into a larger one in a single direction will increase the conjugation length, allowing a fine tuning of electronic properties. Here, we designed and synthesized a unidirectionally extended fused-8-ring based nonfullerene acceptor, AOIC, and bidirectionally extended fused-11-ring electron a...
Article
In this work, a kind of thiophene-fused quinoxaline (QXT) unit has been designed and synthesized as an electron-deficient unit to build two D-A conjugated copolymers (PBDTT-QXT-TF1 and PBDTT-QXT-TF2) with a thiophene ring as “π-bridge” and thienyl substituted benzo[1,2-b:4,5-b’]dithiophene (BDTT) unit as an electron-rich unit, in which two adjacent...
Article
Black phosphorous quantum dots (BPQDs) possess ambipolar charge transport, high mobility, and a tunable direct bandgap. Here, liquid‐exfoliated BPQDs are used as interlayers to modify both the electron transport layer and hole transport layer in organic solar cells (OSCs). The incorporation of BPQDs is beneficial to the formation of a cascade band...
Article
An effective way to improve the power conversion efficiency of organic solar cells (OSCs) is to use the ternary architecture consisting of a donor, an acceptor, and a third component. Identifying the proper third component for successful ternary OSCs, however, is not an easy task. Here, we demonstrate that a middle‐bandgap acceptor, ITC‐2Cl, functi...
Article
We extend the thieno[3,2-b]thiophene and naphthalene cores in our previously reported fused-ring electron acceptors (FREAs) F6IC and IHIC2 to benzo[b]benzo[4,5]thieno[2,3-d]thiophene and naphtho[1,2-b:5,6-b']dithiophene, respectively, and synthesize two new isomeric FREAs BTIC and NTIC. Both BTIC and NTIC exhibit strong absorption from 500 to 800 n...
Article
While there are numerous approaches to functionalize conjugated polymers for organic solar cells (OSCs), one widely adopted approach is fluorination. Of the many different locations for fluorination, one of the least studied is the conjugated linker which connects the donor and acceptor moieties; further, all existing reports primarily explore mono...
Article
Two isomeric fused undecacyclic electron acceptors (FUIC and i-FUIC) are designed and synthesized via one stone two birds strategy based on core unit 4TT (four thienothiophene units condensed with three cyclopentadienyl rings) and end groups 2FIC (2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)-malononitrile). The only difference is the two j...
Article
A star-shaped nonfullerene electron acceptor, FBTIC, and a linear-shaped nonfullerene acceptor, FBDIC, with the same electron-deficient end groups and p-hexylphenyl side chains but different fused-ring electron-rich cores (benzotrithiophene and benzodithiophene) are designed, synthesized, and compared. Terminal groups 2FIC in FBTIC form intermolecu...
Article
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A new fused-chrysene electron-donating core is synthesized, where chrysene is condensed with two thiophenes via two dihydrobenzene rings. Based on this building block coupled with 2 electron-accepting end groups 1,1-dicyanomethylene-3-indanone, a new Z-shaped fused-ring electron acceptor, FCIC, is designed and synthesized. FCIC shows intense absorp...
Article
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Non-fullerene acceptors have recently emerged as promising candidates for Organic Photovoltaics (OPVs) owing to their superior optoelectronic properties. However, the varied lowest unoccupied molecular orbital (LUMO) levels of the acceptors pose difficulty in aligning their energy levels with existing electron transporting layers (ETLs). The author...
Article
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Transparent organic photovoltaics are identified as important components for building‐integrated photovoltaics and smart window technologies. In this work, highly transparent organic solar cells (T‐OSCs) based on all‐near‐infrared (NIR) harvesting materials (optical bandgap, Egopt < 1.4 eV) are first fabricated. Both donor and acceptor materials us...
Article
Poly(3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) have been extensively studied due to unique advantages of P3HT such as roll-to-roll and large-area printing fabrication, but a poor short-circuit current density greatly limits the enhancement of power conversion efficiency (PCE). Herein, via the thiophene-fused aromatic heterocycle as...