Polymers For Organic Photovoltaics Research Articles

Efficient Derivatization of a Thienobenzobisthiazole‐Based π‐Conjugated Polymer Through Late‐Stage Functionalization Towards High‐Efficiency Organic Photovoltaic Cells

AbstractDerivatization is essential for optimizing organic material properties. However, because functional groups are often introduced at an early stage of the synthesis, similar intermediates have to be repeatedly synthesized to produce derivatives, which amounts to a daunting and time‐consuming task. Using thienobenzobisthiazole (TBTz) as a building unit of donor polymers for organic photovoltaics (OPVs), we demonstrate an efficient derivatization of a TBTz‐based π‐conjugated polymer by late‐stage functionalization. In the developed synthetic route, functional groups are introduced at the last step of monomer synthesis, enabling us to easily synthesize several derivatives from a common intermediate. Ester and acyl groups are introduced into the polymer instead of the alkyl group, giving rise to deep HOMO energy levels and resulting in OPV cells with high open‐circuit voltage even in the absence of halogen substituents that are typically introduced into the donor polymers. Notably, the ester‐functionalized TBTz‐based polymer shows a small nonradiative voltage loss (ΔVnr) of 0.19 V and has one of the highest charge generation efficiencies among the halogen‐free donor polymers with similar ΔVnr, improving the critical trade‐off relationship between voltage loss and charge generation. Our results provide an important guideline for the efficient development of high‐performance polymers for OPVs.

Efficient Derivatization of a Thienobenzobisthiazole-Based π-Conjugated Polymer Through Late-Stage Functionalization Towards High-Efficiency Organic Photovoltaic Cells.

Derivatization is essential for optimizing organic material properties. However, because functional groups are often introduced at an early stage of the synthesis, similar intermediates have to be repeatedly synthesized to produce derivatives, which amounts to a daunting and time-consuming task. Using thienobenzobisthiazole (TBTz) as a building unit of donor polymers for organic photovoltaics (OPVs), we demonstrate an efficient derivatization of a TBTz-based π-conjugated polymer by late-stage functionalization. In the developed synthetic route, functional groups are introduced at the last step of monomer synthesis, enabling us to easily synthesize several derivatives from a common intermediate. Ester and acyl groups are introduced into the polymer instead of the alkyl group, giving rise to deep HOMO energy levels and resulting in OPV cells with high open-circuit voltage even in the absence of halogen substituents that are typically introduced into the donor polymers. Notably, the ester-functionalized TBTz-based polymer shows a small nonradiative voltage loss (ΔVnr) of 0.19 V and has one of the highest charge generation efficiencies among the halogen-free donor polymers with similar ΔVnr, improving the critical trade-off relationship between voltage loss and charge generation. Our results provide an important guideline for the efficient development of high-performance polymers for OPVs.

(Z)-4-(thiophen-2-ylmethylene)-4H-thieno[2,3-b]pyrrol-5(6H)-one based polymers for organic photovoltaics

(Z)-4-(thiophen-2-ylmethylene)-4H-thieno[2,3-b]pyrrol-5(6H)-one based polymers for organic photovoltaics

Anthracene / fluorescein based semi-conducting polymer for organic photovoltaics: Synthesis, DFT, optical and electrical properties

A new soluble semi-conducting polymer (AnFL) designed on alternating anthracene and fluorescein photoactive moieties has been synthesized via Williamson polycondensation. Different technics were combined to evidence its structural, optical and electrical properties. NMR and FTIR spectroscopies were used to confirm the macromolecular structure. Optical properties were studied by UV–visible absorption and photoluminescence spectroscopies, evidencing fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) from anthracene core to fluorescein unit which enhance the photovoltaic performance of the polymer. A single-layer [ITO/AnFL/Al] device was elaborated and investigated using current–voltage measurements where a typical diode behavior was observed with a turn-on voltage of 4.4 V. Results show also that the current is well described with space-charge-limited current conduction mechanism, with a charge carrier mobility of 2.38.10−5 cm2V−1s−1. The preliminary photovoltaic characteristics of the nanocomposite AnFL:PCBM were estimated and the blend showed an efficient interfacial charge transfer suggesting good photovoltaic performance for AnFL. All results showed that this functional polymer exhibits motivating photophysical properties and shows promising photovoltaic trends.

Top‐Gate Field‐Effect Transistor as a Testbed for Evaluating the Photostability of Organic Photovoltaic Polymers

Organic Photovoltaic Polymers In article number 2100962, Hyeok Kim and co-workers proposed a top-gate field-effect transistor as a testbed for evaluating the photostability of organic solar cell (OSC) materials. This device test platform features a fluoropolymer gate dielectric to minimize the internal and external origins of photo-instability. In this testbed, the photostability of OSC materials can be simply investigated by monitoring light-induced mobility degradation with minimized extrinsic effects.

High‐Efficiency P3HT‐Based All‐Polymer Solar Cells with a Thermodynamically Miscible Polymer Acceptor

Poly(3‐hexylthiophene) (P3HT) is the most classical conjugated polymer for organic photovoltaics due to its low‐cost and synthetic scalability. However, P3HT‐based organic photovoltaics suffer from inferior device performance with respect to donor–acceptor copolymers. Particularly, the device performance of P3HT‐based all‐polymer solar cells (all‐PSCs) is rather poor due to the challenges in reaching ideal bulk‐heterojunction morphology. Herein, highly efficient P3HT‐based all‐PSCs by blending P3HT with a thermodynamic miscible polymer acceptor are reported. Among the three state‐of‐the‐art polymer acceptors (N2200, PYT, and DCNBT‐IDT), N2200 and PYT are thermodynamically immiscible with P3HT and thus led to excessive phase separation when blended with P3HT, whereas DCNBT‐IDT displayed proper thermodynamic miscibility with P3HT and generated the formation of well‐mixed fibrillary active layer morphology. As a result, a power conversion efficiency of 7.35% has been achieved by P3HT:DCNBT‐IDT blend, which is a new record for P3HT‐based all‐PSCs and largely higher than any previous results. Broad implication for further efficiency enhancement of P3HT‐based all‐PSCs is provided in the results and a promising pathway to realize highly efficient yet cost‐effective solar energy production is suggested.

Naphthobisthiadiazole-Based π-Conjugated Polymers for Nonfullerene Solar Cells: Suppressing Intermolecular Interaction Improves Photovoltaic Performance.

Naphthobisthiadiazole has been known as a promising building unit of π-conjugated polymers for organic photovoltaics (OPVs). Here, we synthesized new NTz-based polymers that were combined with a benzodithiophene (BDT) unit having alkylthienyl substituents in the polymer backbone, named PNTzBDT, and PNTzBDT-F and PNTzBDT-Cl with fluorine and chlorine groups in the substituents, respectively. The polymers had significantly improved solubility than the previously reported NTz-based polymer (PNTz4T), most likely due to the torsion of the alkylthienyl substituents with respect to the BDT moiety, which suppresses the intermolecular interaction between the backbones. Despite the lower intermolecular interaction and thereby lower crystallinity, these polymers, in particular PNTzBDT and PNTzBDT-F, exhibited higher photovoltaic performances, with power conversion efficiencies as high as 13.3%, than PNTz4T in the cells that used Y6 as the acceptor material. The improved performance was ascribed to the enhanced miscibility of the polymers with the nonfullerene acceptor due to the increased solubility, which in addition led to the better charge generation and reduced charge recombination. These results indicate that NTz-based π-conjugated polymers have high potential for nonfullerene-based OPVs.

Top‐Gate Field‐Effect Transistor as a Testbed for Evaluating the Photostability of Organic Photovoltaic Polymers

Light‐induced performance degradation in organic solar cells (OSCs) is a major impediment to their commercialization. As the photostability of OSCs strongly depends on the material's properties, the most effective solution for this concern is to develop a photostable material. However, the wide variety of causes of photo‐instability in a standard multilayered OSC structure complicates the evaluation of photostability of newly developed materials. To address this challenge, a top‐gate field‐effect transistor (FET) as a testbed for evaluating the photostability of OSC materials is proposed. This device test platform minimizes the internal and external origins of photo‐instability by employing a fluoropolymer gate dielectric. The photostability of an OSC material incorporated in this FET testbed can be evaluated by monitoring light‐induced mobility degradation. Two types of common donor polymers with similar chemical structures and crystallinity are employed as test materials, and their photostability is evaluated. The test results correspond to the photostability measurements conducted in the standard OSC structure, validating the proposed FET testbed. The proposed FET testbed enables rapid evaluation of the photostability of a newly developed OSC material, thereby providing timely feedback to material scientists. This boosts the development of photostable OSC materials.

Photostrictive effect in 1-3 composites of photovoltaic and piezoelectric phases: A numerical study

Coalesce of photovoltaic effect with converse piezoelectric effect will turn into a photostrictive phenomenon. The current study conceptualizes a 1-3 photostrictive composite consists of a photovoltaic polymer as matrix and fibers of piezoelectric material. The proposed artificial photostrictive composite is capable of replacing lead-based naturally occurring photostrictive material, not only opening a potential for new applications but also caters to tailor the desired properties. Present study employs poly{4,8-bis[5-(2-ethyl-hexyl)thiophen-2-yl]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the fibers. A representative volume element technique (RVE) is employed to embrace the local variation of multi-physics properties. The actuation response of cantilever and simply supported beam bonded to photostrictive composite patch is accurately predicted by finite element method, while discretizing the structure with degenerated shell element. Photostrictive composite with 60% volume fraction of fibers, arranged in square pattern have deflected the cantilever tip to 1.95 mm. Therefore, we provide 1-3 photostrictive composite as a solution for future wireless and lightweight vibration control applications.

Novel photostrictive 0-3 composites: A finite element analysis

Simultaneous action of photovoltaic effect and converse piezoelectric effect will induce the photostrictive effect. In contrast to the naturally occurring photostrictive material, the present study proposes a 0-3 photostrictive composite. The current photostrictive composite comprises of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the particulates. The current study shows that the present 0-3 photostrictive composite is a suitable alternative for the most popular lead-based photostrictive material. While evaluating all the effective elastic, dielectric, piezoelectric, and pyroelectric properties of 0-3 photostrictive composite, the effect of local fluctuations was incorporated in representative volume element (RVE) using the finite element method. A finite element formulation using a degenerated shell element is derived to simulate the actuation response of the proposed 0-3 photostrictive composite. Numerical studies have been performed on cantilever and simply supported beams. The maximum tip and center deflection of cantilever beam and simply supported beam bonded with 0-3 photostrictive patch is mm and mm, respectively. The maximum value of the effective piezoelectric coefficient effective thermal expansion coefficient effective Young’s modulus and effective pyroelectric coefficient of proposed 0-3 photostrictive composite are m/V, 4.59 1.63 N/m2, and 7.57 C/m2 K, respectively, obtained at 25% volume fraction of particulates. This study opens possibilities of photostrictive coupling in composites.

Solubilizing Side Chain Engineering: Efficient Strategy to Improve the Photovoltaic Performance of Novel Benzodithiophene-Based (X-DADAD)n Conjugated Polymers.

Conjugated polymers represent a promising family of semiconductor materials for thin-film organic solar cells (OSCs). An efficient approach to improve the photovoltaic performance of conjugated polymers is engineering the side chains attached to the polymer backbone. This work reports the impact of different alkyl substituents on the optoelectronic properties, charge carrier mobilities, thin film morphology, and photovoltaic performance of novel (X-DADAD)n conjugated polymers incorporating benzo[1,2-b:4,5-b']dithiophene moieties. It has been shown that loading conjugated polymers with appropriate alkyl side chains results in a spectacular performance improvement from 6.8% to 9% in OCSs using a model fullerene acceptor [6,6]-phenyl-C71 -butyric acid methyl ester. The obtained results feature side-chain engineering as a facile and efficient strategy for designing high-performance conjugated polymers for organic photovoltaics.

Side chain engineering of quinoxaline-based small molecular nonfullerene acceptors for high-performance poly(3-hexylthiophene)-based organic solar cells

Poly(3-hexylthiophene) (P3HT) is one of the most used semiconducting polymers for organic photovoltaics because it has potential for commercialization due to its easy synthesis and stability. Although the rapid development of the small molecular non-fullerene acceptors (NFAs) have largely improved the power conversion efficiency (PCE) of organic solar cells (OSCs) based on other complicated p-type polymers, the PCE of P3HT-based OSCs is still low. In addition, the design principle and structure-properties correlation for the NFAs matching well with P3HT are still unclear and need to be investigated in depth. Here we designed a series of NFAs comprised of acceptor (A) and donor (D) units with an A2-A1-D-A1-A2 configuration. These NFAs are abbreviated as Qx3 , Qx3b and Qx3c , where indaceno[1,2- b :5,6- b′ ]dithiophene (IDT), quinoxaline (Qx) and 2-(1,1-dicyanomethylene)rhodanine serve as the middle D, bridged A1 and the end group A2, respectively. By subtracting the phenyl side groups appended on both IDT and Qx skeletons, the absorption spectra, energy levels and crystallinity could be regularly modulated. When paired with P3HT, three NFAs show totally different photovoltaic performance with PCEs of 3.37% (Qx3) , 6.37% (Qx3b) and 0.03% (Qx3c) , respectively. From Qx3 to Qx3b , the removing of phenyl side chain in the middle IDT unit results in the increase of crystallinity and electron mobility. However, after subtracting all the grafted phenyl side groups on both IDT and Qx units, the final molecule Qx3c exhibits the lowest PCE of only 0.03%, which is mainly attributed to the serious phase-separation of the blend film. These results demonstrate that optimizing the substituted position of phenyl side groups for A2-A1-D-A1-A2 type NFAs is vital to regulate the optoelectronic property of molecule and morphological property of active layer for high performance P3HT-based OSCs.

A New Method for the Synthesis of Bromine-Containing Heterocyclic Compounds for Photovoltaic Polymers

With the development and improvement of systems for converting sunlight into electric and thermal energy, more and more work is emerging on the development of the newest and most promising direction in solar energy, namely the creation of solar cells based on photosensitive polymers. Recently the power conversion efficiency of organic photovoltaic (OPV) devices has overcome the barrier of 17%, and thus we can expect a new wave of scientific interest in the development of new, more efficient OPV devices. Unfortunately, during searching for highly efficient chemical structures of OPV polymers, the researchers missed an important point: all photovoltaic polymers consist of aromatic and heteroaromatic «building blocks», which, in turn, are synthesized based on outdated techniques using highly toxic, dangerous for life and environment precursors. The development of «green», environmentally friendly, economically viable methods for the synthesis of photovoltaic polymers and building blocks for their production, will make the energy obtained from OPV truly «green». In this work, we present an alternative, «green» method for synthesizing halogen-containing aromatic and heteroaromatic, expensive building blocks most commonly used in the synthesis of photovoltaic polymers, which can be used to obtain photovoltaic polymers of various structures. We present the original methods for the synthesis of 4,4-dibromo-1,1- biphenyl (1), 4,7-dibromo-2,1,3-benzothiadiazole (2), 2-bromothiophene (3) and 2,5-dibromothiophene (4). All these methods differ from the previously described routes by their simplicity and convenience of their implementation, the absence of corrosive and irritant reagents, good yield and compliance with the principles of «Green Chemistry».

Fluctuations in the Emission Polarization and Spectrum in Single Chains of a Common Conjugated Polymer for Organic Photovoltaics

Measuring the nanoscale organization of conjugated polymer chains used in organic photovoltaic (OPV) blends is vital if one wants to understand the materials. This is made very difficult with high efficiency OPV polymers such as PTB7 that form aggregates, as a lack of periodicity and a high degree of disorder make understanding of the nanoscale organization challenging. Here, single molecule spectroscopy is used to observe single chains and aggregates of PTB7. Using four detectors the photoluminescence intensity, wavelength, polarization, and lifetime are simultaneously monitored. Fast (milliseconds) and slow (seconds) fluctuations are observed over a time window of 30 s in all of these observables from single aggregates and chains as individual chromophores activate and deactivate, leading to dynamical changes in the emission spectrum and dipole orientation. This information can be used to help reconstruct the spatial and spectral organization of disordered aggregates of PTB7, thereby adding valuable new information on how the chains are arranged in space.

Electronic structure theory gives insights into the higher efficiency of the PTB electron-donor polymers for organic photovoltaics in comparison with prototypical P3HT.

The electron donor poly-thienothiophene-benzodithiophene (PTB) polymer series displays remarkable properties that lead to more efficient bulk heterojunction (BHJ) organic solar cells. In this work, the ground and four excited states (bright S 1 and dark S 2-S 4) of three different members of the PTBn (n = 1, 6, 7) series were studied and compared with the prototypical poly(3-hexylthiophene) (P3HT) donor polymer. Time-dependent density functional theory was employed to investigate oligomers of similar sizes (∼50 Å). Charge alternation electron accumulation and depletion regions of the four transitions are concentrated on the inner units, thereby favoring interaction with the electron acceptor in a BHJ. The bright S 1 transition energies of PTBn are about 0.2 eV lower as compared to P3HT, thereby allowing a better match of their levels with the typical C60-type acceptor moiety in a BHJ. Side chains play a minor role in the electronic spectrum (less than ∼0.1 eV). The most efficient PTB7 transfers more electronic charge from its electron-rich benzodithiophene subunit to its electron-deficient thieno[3,4-b] thiophene subunit as compared to PTB1 and PTB6. We show that the dipolar effect, a partial concentration of negative and positive charges on the different parts of the donor polymer that favors charge separation, is more pronounced in PTBn polymers and typically an order of magnitude larger as compared to P3HT. These effects are conspicuous for the most efficient polymer of the series, PTB7, with its fluorine substituent shown to play a crucial role.

Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics

As many conjugated polymer-based organic photovoltaic (OPV) materials provide substantial solar power conversion efficiencies (as high as 13%), it is important to develop a deeper understanding of how the primary repeat unit structures impact device performance. In this work, we have varied the group 14 atom (C, Si, Ge) at the center of a bithiophene fused ring to elucidate the impact of a minimal repeat unit structure change on the optical, transport, and morphological properties, which ultimately control device performance. Careful polymerization and polymer purification produced three “one-atom change” donor–acceptor conjugated alternating copolymers with similar molecular weights and dispersities. DFT calculation, absorption spectroscopy, and high-temperature solution 1H nuclear magnetic resonance (NMR) results indicate that poly(dithienosilole-alt-thienopyrrolodione), P(DTS-TPD), and poly(dithienogermole-alt-thienopyrrolodione), P(DTG-TPD) exhibit different rotational conformations when compared to poly(cyclopentadithiophene-alt-thienopyrrolodione), P(DTC-TPD). Solid-state 1H MAS NMR experiments reveal that the greater probability of the anticonformation in P(DTS-TPD) and P(DTG-TPD) prevail in the solid phase. The conformational variation seen in solution and solid-state NMR in turn affects the polymer stacking and intermolecular interaction. Two-dimension 1H-1H DQ-SQ NMR correlation spectra shows aromatic–aromatic correlations for P(DTS-TPD) and P(DTG-TPD), which on the other hand is absent for P(DTC-TPD). In a thin-film interchain packing study using grazing incidence wide-angle X-ray scattering (GIWAXS), we observe the π-face of the conjugated backbones of P(DTC-TPD) aligned edge-on to the substrate, whereas in contrast the π-faces of P(DTS-TPD) and P(DTG-TPD) align parallel to the surface. These differences in polymer conformations and backbone orientations lead to variations in the OPV performance of blends with the fullerene PC71BM, with the device containing P(DTC-TPD):PCBM having a lower fill factor and a lower power conversion efficiency. Ultrafast transient absorption spectroscopy shows the P(DTC-TPD):PCBM blend to have a more pronounced triplet formation from bimolecular recombination of initially separated charges. With a combination of sub-bandgap external quantum efficiency measurements and DFT calculations, we present evidence that the greater charge recombination loss is the result of a lower lying triplet energy level for P(DTC-TPD), leading to a higher rate of recombination and lower OPV device performance. Importantly, this study ties ultimate photovoltaic performance to morphological features in the active films that are induced from the processing solution and are a result of minimal one-atom differences in polymer repeat unit structure.

Impact of solution temperature-dependent aggregation on the solid-state packing and electronic properties of polymers for organic photovoltaics

The impact of solution temperature-dependent aggregation of PffBT4T-2OD and PBT4T-2OD polymers on their electronic and solid-state packing properties is investigated using MD simulations and DFT calculations.

Thiophene-Fused Naphthalene Diimides: New Building Blocks for Electron Deficient π-Functional Materials

Abstract Development of novel π-conjugated building blocks that can be integrated into molecular or macromolecular systems is key to the evolution of new superior organic semiconductors utilized as the active materials in organic electronics devices such as organic field-effect transistors (OFETs), organic photovoltaics (OPVs), and organic thermoelectric (TE) devices. This review affords a brief overview of thiophene-fused naphthalene diimide (NDI), namely naphtho[2,3-b:6,7-b′]dithiophene diimide (NDTI) and naphtho[2,3-b]thiophene diimide (NTI), recently developed as novel electron deficient building blocks for n-type and ambipolar organic semiconductors. These thiophene-fused NDI building blocks had not been known until 2013 owing to their synthetic difficulty; more precisely, the difficulty in attaching fused-thiophene ring(s) on the NDI core. We have successfully established a thiophene-annulation reaction on ethyne-substituted NDI derivatives, which allows us to elaborate various NDTI and NTI derivatives. The key features of these building blocks are low-lying energy levels of lowest unoccupied molecular orbitals (LUMO, 3.8–4.1 eV below the vacuum level) and easy functionalizability of the thiophene α-positions, which allows their derivatives and polymers to conjugate efficiently with additional π- and co-monomer units. These features make the NDTI- and NTI-derivatives and polymers promising n-type and ambipolar materials for OFETs and acceptors for OPVs. In fact, various useful materials have already been derived from the NDTI and NTI building blocks: air-stable n-type small molecules and polymers with high electron mobility (∼0.8 cm2 V−1 s−1), ambipolar oligomers and polymers with well-balanced hole and electron mobilities, doped n-type semiconductors affording bulk conductors applicable to n-type TE materials, and electron acceptor molecules and polymers for OPVs showing promising power conversion efficiencies of up to 9%. These impressive and diversified device performances testify the usefulness of thiophene-fused NDI building blocks in the development of new electron deficient π-functional materials.

Optimization of the power conversion efficiency in high bandgap pyridopyridinedithiophene-based conjugated polymers for organic photovoltaics by the random terpolymer approach

We report that the organic photovoltaic (OPV) performance of wide band gap pyridopyridinedithiophene-based conjugated polymers can be significantly improved by employing the random terpolymer approach for the development of new pyridopyridinedithiophene-based conjugated polymers. This is demonstrated by the synthesis of the alternating copolymer (P1) consisting of 3,3′-difluoro-2,2′-bithiophene and pyridopyridinedithiophene and the random terpolymer (P2) containing pyridopyridinedithiophene 3,3′-difluoro-2,2′-bithiophene and thiophene. OPV devices fabricated by P1 and P2 in combination with PC61BM and PC71BM in an inverted device configuration exhibited power conversion efficiencies (PCEs) of 1.5% and 4.0%, respectively. We identified that the main reason for the enhanced performance of the OPV devices based on the P2 random copolymer was the improved morphology (miscibility) between P2 and PCBM as compared to P1. More specifically, atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies revealed that the P1 based films showed rougher surface with clear crystallization/precipitation of the polymer chains even after the addition of chloronaphthalene (CN) to the chloroform processing solvent which significantly limited the short circuit current density (JSC), fill factor (FF) and overall performance of the prepared photovoltaic devices. On the other hand, P2 based films showed better miscibility with the acceptor particularly when processed using 5% CN containing chloroform solvent giving a respectable improvement in the PCE of the photovoltaic devices.

Furan-containing conjugated polymers for organic solar cells

Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.