High-Performance All-Polymer Solar Cells Achieved by Fused Perylenediimide-Based Conjugated Polymer Acceptors

Perylene Diimide-based Non-fullerene Acceptors With A-D-A'-D-A Architecture For Organic Solar Cells

The vinylene-bridged helical PDI dimer (PDI2) has been an alternative PDI building block for non-fullerene acceptor (NFAs). However, the development of PDI2 derivatives still lag behind, and most of PDI2 derivatives based organic solar cells (OSCs) only achieved a moderate power conversion efficiencies (PCE) of less than 8%. In this contribution, an acceptor-donor-acceptor-donor-acceptor (A-D-A'-D-A) architecture was introduced to facilitate the improvement of photovoltaic properties. Two acceptors named diIDTIC-PDI2 and diFIDTIC-PDI2 were designed and synthesized, in which a PDI2 moiety flanked with two indacenodithiophene (IDT) units was employed as the D-A'-D core and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) or fluorinated IC (IC2F) acted as terminal groups, respectively. The photovoltaic performances of these two acceptors were explored using PM1 as the electron donor. Compared to diIDTIC-PDI2, the fluorinated diFIDTIC-PDI2 based OSCs obtained enhanced photovoltaic performance with the best PCE of 9.77%, a V_OC of 0.957 V, J_SC of 13.58 mA cm^-2 and FF of 75.1%. These results illustrate that engineering terminal groups is a robust strategy of enhancing the efficiency of PDI based acceptors with A-D-A'-D-A architecture.

An investigation of palladium-catalyzed Stille-type cross-coupling of nitroarenes in perylenediimide series

We report herein an unprecedented palladium-catalyzed cross-coupling reaction between mononitro-perylenediimide (PDI) and various arylstannanes. Optimized conditions developed with this Stille-type reaction allow the grafting of (hetero)aryls of various electronic nature in the bay region of PDIs. Moreover, we capitalized on the high selectivity of this cross-coupling through the desymmetrization of the dinitro-PDI substrate.

Structural symmetry-breaking of perylene diimide acceptor at N-position for enhanced photovoltaic performance

The vinylene-bridged helical perylene diimide dimer (PDI2) and derivatives have received considerable attention for application in nonfullerene organic solar cells (OSCs). Benefit from the large natural dipole moment and the...

Perylene Diimide-Based Conjugated Polymers for All-Polymer Solar Cells

In recent decades, non-fullerene acceptors (NFAs) are undergoing rapid development and emerging as a hot area in the field of organic solar cells. Among the high-performance non-fullerene acceptors, aromatic diimide-based electron acceptors remain to be highly promising systems. This review discusses the important progress of perylene diimide (PDI)-based polymers as non-fullerene acceptors in all-polymer solar cells (all-PSCs) since 2014. The relationship between structure and property, matching aspects between donors and acceptors, and device fabrications are unveiled from a synthetic chemist perspective.

π-Extension, Selenium Incorporation, and Trimerization: "Three in One" for Efficient Perylene Diimide Oligomer-Based Organic Solar Cells

Perylene diimide (PDI) and the vinylene-bridged helical PDI oligomers are versatile building blocks for constructing nonfullerene acceptors (NFAs). In this contribution, a benzene-cored star-shaped NFA, namely, TPDI2-Se, was designed and synthesized for organic solar cells (OSCs). The NFA with smaller π-conjugated blades, namely, TPDI-Se, was synthesized for comparison. Using the commercially available PTB7-Th as the electron donor, the best power conversion efficiency (PCE) of 3.62% was obtained for TPDI-Se-based OSCs. However, a much higher PCE of 8.59% was achieved for TPDI2-Se-based devices owing to the π-extension in the peripheral panels. Moreover, the photovoltaic performance of TPDI2-Se-based OSCs is also superior to those of the parent NFA TPDI2 (PCE of 7.84%)- and the blade moiety PDI2-Se (PCE of 6.61%)- based ones. Additionally, a remarkable short-circuit current (J_sc) value of 17.21 mA/cm² was obtained for TPDI2-Se-based OSCs, which is among the highest J_sc values reported in PDI-based OSCs. These results argue that the so-called "three in one" molecule design strategy of π-extension, selenium incorporation, and trimerization offers a robust approach to constructing high-performance PDI-based NFAs.

Aromatic-Diimide-Based n-Type Conjugated Polymers for All-Polymer Solar Cell Applications

All-polymer solar cells (all-PSCs) have attracted immense attention in recent years due to their advantages of tunable absorption spectra and electronic energy levels for both donor and acceptor polymers, as well as their superior thermal and mechanical stability. The exploration of the novel n-type conjugated polymers (CPs), especially based on aromatic diimide (ADI), plays a vital role in the further improvement of power conversion efficiency (PCE) of all-PSCs. Here, recent progress in structure modification of ADIs including naphthalene diimide (NDI), perylene diimide (PDI), and corresponding derivatives is reviewed, and the structure-property relationships of ADI-based CPs are revealed.

Manipulating Polymer Donors Toward a High-Performance Polymer Acceptor Based On a Fused Perylenediimide Building Block With a Built-In Twisting Configuration

A novel fused perylene diimide (PDI)-based polymer electron acceptor (PFPDI-BDF) with a built-in twisting configuration was constructed for application in all-polymer solar cells (all-PSCs). To shed light on the compatibility of the FPDI polymer acceptor and to identify a suitable polymer donor for device applications, we considered herein to investigate three polymer donors (PBDB-T, PTB7-Th, and PCPDTFBT) with different optical and electronic properties as well as polymer chain packing behavior for comparing the device performance. After being fabricated with PFPDI-BDF, polymer donor PBDB-T with a wide band gap showed a decent power conversion efficiency (PCE) of 4.86% with an open-circuit voltage (V_oc) of 0.82 V, a short-circuit current density (J_sc) of 8.94 mA cm^-2, and a recorded fill factor (FF) of 66.3%, which is one of the best FF reported for PDI-based all-polymer solar cells (all-PSCs). The enhanced efficiency of 6.05% was found in the medium band gap polymer PTB7-Th devices due to the more complementary absorption region that makes the photoactive blends absorb more photons, giving rise to an increased J_sc of 12.97 mA cm^-2. On the other hand, due to the inferior exciton dissociation/extraction efficiency and unfavorable morphology compatibility, the narrow band gap polymer donor PCPDTFBT/PFPDI-BDF devices exhibited the worst PCE of only 0.71% with a low J_sc of 2.2 mA cm^-2 and a FF of 42.4%.

Dual Imide-Functionalized Unit-Based Regioregular D-A1-D-A2 Polymers for Efficient Unipolar n-Channel Organic Transistors and All-Polymer Solar Cells

The demand for the development of more promising n-type semiconducting polymers with excellent electron mobilities and air stabilities is growing fast. In this study, we designed and synthesized a series of new dual imide-functionalized derivative-based regioregular D-A₁-D-A₂ copolymers with different side chains (namely, PNT-R, R = 2-decyltetradecyl (DT), 2-octadecyldodecyl (OD), and 2-hexyldecyl (HD)). These new polymers PNT-R showed strong electron affinities with deep lowest unoccupied molecular orbital (LUMO) levels down to -4.01 eV, indicating that they are promising electron-transporting materials. To optimize the electron mobility, side-chain engineering was adopted. Thus, the effects of the side-chain length on their optoelectronic and charge-transport properties as well as the performances of all-polymer solar cells (all-PSCs) were systematically investigated. Shortening the side-chain length significantly expanded the absorption range, deepened the LUMO energy level, strengthened the molecular packing properties, and developed more crystalline microstructures in the solid state, as evidenced by the ultraviolet-visible absorption spectra, cyclic voltammetry, synchrotron two-dimensional grazing-incidence wide-angle X-ray scattering, and atomic force microscopy measurements. Consequently, the highest electron mobility of 1.05 cm² V^-1 s^-1 was achieved in PNT-HD-based organic thin-film transistors (OTFTs). Also, PNT-R polymers were successfully applied as electron acceptors in all-PSCs. In good agreement with the OTFT results, the highest power conversion efficiency of 6.62% was obtained for the PNT-HD-blend film due to its excellent short-circuit current ( J_sc) value (12.07 mA cm^-2), which was much higher than that of the PNT-DT- and PNT-OD-based all-PSCs (7.67 and 10.19 mA cm^-2, respectively). By further investigating the dependence of the J_sc and open-circuit voltage ( V_oc) on the illuminated light intensity ( P), the high J_sc value of the PNT-HD-based device was found to originate from its highly suppressed mono- and bimolecular recombination as well as efficient exciton dissociation and charge transfer at the donor-acceptor interfaces. Overall, this study provides insights into the naphthalenediimide-based regioregular D-A₁-D-A₂ copolymers used in all-PSCs and offers important design guidelines for future development of n-type semiconducting polymers.

Recent Advances in n-Type Polymers for All-Polymer Solar Cells

All-polymer solar cells (all-PSCs) based on n- and p-type polymers have emerged as promising alternatives to fullerene-based solar cells due to their unique advantages such as good chemical and electronic adjustability, and better thermal and photochemical stabilities. Rapid advances have been made in the development of n-type polymers consisting of various electron acceptor units for all-PSCs. So far, more than 200 n-type polymer acceptors have been reported. In the last seven years, the power conversion efficiency (PCE) of all-PSCs rapidly increased and has now surpassed 10%, meaning they are approaching the performance of state-of-the-art solar cells using fullerene derivatives as acceptors. This review discusses the design criteria, synthesis, and structure-property relationships of n-type polymers that have been used in all-PSCs. Additionally, it highlights the recent progress toward photovoltaic performance enhancement of binary, ternary, and tandem all-PSCs. Finally, the challenges and prospects for further development of all-PSCs are briefly considered.

Regioregular and Regioirregular Poly(selenophene-perylene diimide) Acceptors for Polymer-Polymer Solar Cells

We report two new regioregular and regioirregular model copolymer acceptors based on selenophene and perylenetetracarboxylic diimide moieties, respectively, named RR-P(SePDI) and RI-P(SePDI), which were synthesized to study how regioregularity impacts the properties of resulting polymers. The structural regioregularity impact on the performance of polymer-polymer solar cells (PPSCs) was highlighted. Both the copolymer acceptors displayed similar optoelectronic properties. The regioregular RR-P(SePDI) exhibited better and balance bulk charge-transport capability than regioirregular RI-P(SePDI) in active layer films. The typical PPSCs based on the regioirregular RI-P(SePDI) copolymer acceptor and the PTB7-Th polymer donor afforded average power conversion efficiencies (PCEs) of about 5.3%. Importantly, reasonably improved average PCEs of about 6.2% were provided by the blend active layer of new regioregular RR-P(SePDI) and PTB7-Th. These results highlight the significant and efficient strategy of rational control regioregularity of the polymer backbone to gain high PCE values in perylene diimide-based PPSCs.