Combining Facile Synthetic Methods with Greener Processing for Efficient Polymer‐Perylene Diimide Based Organic Solar Cells

Abstract

investigated, those based upon the perylene diimide (PDI) skeleton have been extensively studied. [11,12] The PDI chromophore exhibits strong visible light absorption up to ≈600 nm, making it brilliant red in color, and a complimentary absorber to many common high-performance donor polymers. In addition, the dye is a good electron transporting material, is photochemically stable, and can be easily functionalized at the bay, headland, and/or imide position allowing for a myriad of structures to be developed. [13] It has been well documented that monomeric PDI materials often exhibit a strong tendency to aggregate, leading to poor quality bulk heterojunction (BHJ) films and sub-par OSC performance. [14][15][16][17] Dimerization of the PDI chromophores, the formation of higher number oligomers, or polymerization results in nonplanar arrangement of the PDI units, limiting aggregate formation, leading to high performance OSCs. [18][19][20] To date the record PCE for a PDI-based OSC is 9.5%, and is achieved using a dimeric PDI species [21] consisting of two PDI units linked via a spirofluorene building block. Directly linking two PDI mole cules together at the bay position is another strategy to create PDI dimers with highly twisted geometries that lead to good performing OSCs. [22,23] Our research team and others have built upon this concept and developed a series of "annulated" PDI dimers. Annulation at the bay position with sulfur, [24] selenium, [25] or nitrogen [26] has led to several new NFAs that can achieve PCEs above 7% when paired with polymer donors.A key feature to the N-annulated PDI dimers is that the pyrrolic N-atoms offer an additional site for functionalization and open the possibility of side-chain engineering, a valuable tool to tune the BHJ morphology. [27,28] In addition, the dimers can be processed into ordered films using environmentally friendly solvents, [29] which is an important parameter when considering up-scaling. [30][31][32][33] In this work, we report on green-solvent-processable OSCs based on N-annulated PDI dimers and the commercial polymer PTB7-Th. A series of eight different PDI dimers having different alkyl chain lengths and branching points were synthesized and characterized. Through side-chain engineering of the N-annulated PDI dimers, OSC PCEs of 6.6% were achieved.Through ease of scalability and facile synthetic methods, eight N-annulated perylene diimide dimers with different aliphatic chains are synthesized and evaluated as non-fullerene acceptors in organic solar cells (OSCs). Optical absorption and emission spectroscopy, and cyclic voltammetry are used to characterize the materials. Variation of the length and topology of the aliphatic chains attached at the pyrrolic N-position is shown to have minimal effect on properties in solution. As films, the use of a branched aliphatic chains results in the dimer exhibiting a low energy shoulder in the absorption spectrum and a narrower emission band. OSCs are fabricated and tested in air, at room temperature, using an inverted arch...

Synthesis of a Perylene Diimide Dimer with Pyrrolic N–H Bonds and N‐Functionalized Derivatives for Organic Field‐Effect Transistors and Organic Solar Cells

“…OSCs were constructed using the inverted architecture and all active layers processed under ambient conditions from 2Me-THF (see SI for full details). In addition, this PCE value is comparable to OSC fabricated using a PTB7-Th:5 active layer, [30] thus highlighting the potential of the quinoxaline based polymer TTFQx-T1 to be a great partner for PDI based non-fullerene acceptors. OSCs with a TTFQx-T1:5 active layer gave best PCEs of 6.3 % (Figure 8, Table 1).…”

“…This result is very impressive for green solvent, air processed OSCs. In addition, this PCE value is comparable to OSC fabricated using a PTB7-Th:5 active layer, [30] thus highlighting the potential of the quinoxaline based polymer TTFQx-T1 to be a great partner for PDI based non-fullerene acceptors. This is important as TTFQx-T1 is much easily to synthesize than PTB7-Th.…”

Interlayer Engineering of Flexible and Large Area Red Organic Light Emitting Diodes Based on a N-Annulated Perylene Diimide Dimer

“…PEDOT:PSS (poly(ethylenedioxythiophene)/polystyrenesulfonate, Al 4083), which is one of the most commonly used PEDOT:PSS formulations for the HIL, was purchased from Heraeus Precious Metals. tPDI2N-EH ( max emission = 640 nm, film quantum yield (QY) ~16%) was synthesised as previously reported 24 . PFO was purchased from Ossila and used as received.…”

Organic Solar Cell Materials toward Commercialization

“…These results firmly confirm that the green solvent 2‐MeTHF is a promising alternative to the traditional halogenated solvents for promoting environmental‐friendly OSCs. More recently, green solvents were also successfully applied in the large‐area printing device by blade coating method . Recently, Ye et al achieved a PCE of nearly 11% in blade‐coated FTAZ:IT‐M devices using toluene as solvent, which was demonstrated to have an excellent air‐tolerance properties.…”

“…More recently, green solvents were also successfully applied in the large-area printing device by blade coating method. [70][71][72][73] Recently, Ye et al [72] achieved a PCE of nearly 11% in bladecoated FTAZ:IT-M devices using toluene as solvent, which was demonstrated to have an excellent air-tolerance properties. In this work, they also pointed out that the selection of nonchlorinated solvents not only alters the face-on orientation, but also significantly affects the domain purities and length scales of phase separation of the blade-coated nonfullerene OSCs.…”