A 3‐Fluoropyridine Manipulating the Aggregation and Fibril Network of Donor Polymers for Eco‐Friendly Solution‐Processed Versatile Organic Solar Cells

Abstract

The development of eco‐friendly solvent‐processed organic solar cells (OSCs) suitable for industrial‐scale production should be now considered the imperative research. Herein, asymmetric 3‐fluoropyridine (FPy) unit is used to control the aggregation and fibril network of polymer blends. Notably, terpolymer PM6(FPy = 0.2) incorporating 20% FPy in a well‐known donor polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b’]dithiophene))‐alt‐(5,5‐(1’,3’‐di‐2‐thienyl‐5’,7’‐bis(2‐ethylhexyl)benzo[1’,2’‐c:4’,5’‐c’]dithiophene‐4,8‐dione)] (PM6) can reduce the regioregularity of the polymer backbone and endow them with much‐enhanced solubility in eco‐friendly solvents. Accordingly, the excellent adaptability for fabricating versatile devices based on PM6(FPy = 0.2) by toluene processing is demonstrated. The resulting OSCs exhibit a high power conversion efficiency (PCE) of 16.1% (17.0% by processed with chloroform) and low batch‐to‐batch variation. Moreover, by controlling the donor‐to‐acceptor weight ratio at 0.5:1.0 and 0.25:1.0, semi‐transparent OSCs (ST‐OSCs) yield significant light utilization efficiencies of 3.61% and 3.67%, respectively. For large‐area (1.0 cm2) indoor OSC (I‐OSC), a high PCE of 20.6% is achieved with an appropriate energy loss of 0.61 eV under a warm white light‐emitting diode (3,000 K) with the illumination of 958 lux. Finally, the long‐term stability of the devices is evaluated by investigating their structure–performance–stability relationship. This work provides an effective approach to realizing eco‐friendly, efficient, and stable OSCs/ST‐OSCs/I‐OSCs.

High-Performance Poly(3-hexyl thiophene)-Based Organic Photovoltaics with Side-Chain Engineering of Core Units of Small Molecule Acceptors

“…The height profiles of the images of the (a)­P3HT:Y1-IO2F, (b)­P3HT:Y1-IO2Cl, (c)­P3HT:Y6-IO2F, and (d)­P3HT:Y6-IO2Cl films yielded root-mean-square (RMS) surface roughness values of 2.25, 1.75, 4.28, and 4.07 nm, respectively. The P3HT:Y1-IO2F and P3HT:Y1-IO2Cl films exhibited smaller roughness values as compared to that of the P3HT:Y6-IO2F and P3HT:Y6-IO2Cl films, suggesting that Y6-IO2F and Y6-IO2Cl, with a TPBT core, facilitate rougher interfacial contacts and enhance the contact area, resulting in more efficient extraction of charge carriers from the active layer to the anode. , In order to enhance our understanding of the miscibility between P3HT and the four SMAs, we conducted contact angle measurements for each individual acceptor, as presented in Figure S6. The surface energies of P3HT, Y1-IO2F, Y1-IO2Cl, Y6-IO2F, and Y6-IO2Cl obtained were 17.21, 16.03, 15.55, 34.17, and 24.53 mN m –1 , respectively.…”

Distribution of dual additives enables efficient semi-transparent layer-by-layer architecture of organic solar cells

“…11,12 Very recently, our group has reported a terpolymeric PM6 (FPy = 0.2) with 20% 3-fluoropyridine instead of BDD in the PM6 building block, which significantly improved its solubility in eco-friendly solvents and demonstrated its great potential for efficient and versatile OSCs. 13 In addition, various techniques such as a ternary strategy based on BDT-derived donors have been applied to fabricate efficient devices. From these efforts, recent power conversion efficiencies (PCEs) have reached over 19%.…”

“…In this study, we fabricated an efficient device using the LBL method with dual additives such as 1-chloronapthalene (CN) and poly(dimethylsiloxane- co -diphenylsiloxane), dihydroxy terminated (PDMDP) that affect the morphology formation of PM6(FPy = 0.2), which was reported in previous our work. 13 Both additives were introduced into the PM6(FPy = 0.2) layer and the acceptor layer was then coated on the top to form the LBL-processed p–i–n morphology. Specifically, we examined the changes in the photoactive layer with and without heat treatment after mixing two additives separately.…”

Bicontinuous donor and acceptor fibril networks enable 19.2% efficiency pseudo‐bulk heterojunction organic solar cells

“…[17][18][19][20] As discussed in previous works, [21][22][23][24] fibrillation refers to the self-assembly of materials growing in a specific direction to obtain one-dimensional structure and has been demonstrated to require different organization dynamics for materials with different structures. For example, with long backbones, conjugated polymers could easily assemble through main chains to form fibrils [25,26] or ribbons. [27] On the other side, small molecules such as small molecular nonfullerene acceptors (NFAs) only exhibit weak van der Waals force among their adjacent molecules, [28,29] and hence enhanced main-chain interactions (e.g., between the electron-withdrawing end groups) [30] or reduced sidechain interactions [31] are generally required to promote their growth along the conjugated plane.…”