Bispentafluorophenyl-Containing Additive: Enhancing Efficiency and Morphological Stability of Polymer Solar Cells via Hand-Grabbing-Like Supramolecular Pentafluorophenyl–Fullerene Interactions

Abstract

A new class of additive materials bis(pentafluorophenyl) diesters (BFEs) where the two pentafluorophenyl (CF) moieties are attached at the both ends of a linear aliphatic chain with tunable tether lengths (BF5, BF7, and BF13) were designed and synthesized. In the presence of BF7 to restrict the migration of fullerene by hand-grabbing-like supramolecular interactions induced between the CF groups and the surface of fullerene, the P3HT:PCBM:BF7 device showed stable device characteristics after thermal heating at 150 °C for 25 h. The morphologies of the active layers were systematically investigated by optical microscopy, grazing-incidence small-angle X-ray scattering (GISAXS), and atomic force microscopy. The tether length between the two CF groups plays a pivotal role in controlling the intermolecular attractions. BF13 with a long and flexible tether might form a BF13-fullerene sandwich complex that fails to prevent fullerene's movement and aggregation, while BF5 with too short tether length decreases the possibility of interactions between the CF groups and the fullerenes. BF7 with the optimal tether length has the best ability to stabilize the morphology. In sharp contrast, the nonfluorinated BP7 analogue without CF-C physical interactions does not have the capability of morphological stabilization, unambiguously revealing the necessity of the CF group. Most importantly, the function of BF7 can be also applied to the high-performance PffBT4BT-2OD:PCBM system, which exhibited an original PCE of 8.80%. After thermal heating at 85 °C for 200 h, the efficiency of the PffBT4BT-2OD:PCBM:BF7 device only decreased slightly to 7.73%, maintaining 88% of its original efficiency. To the best of our knowledge, this is the first time that the thermal-driven morphological evolution of the high-performance PffBT4BT-2OD polymer has been investigated, and its morphological stability in the inverted device can be successfully preserved by the incorporation of BF7. This research also demonstrates that BF7 is not only effective with PCBM but also to PCBM.

Simultaneous enhanced efficiency and thermal stability in organic solar cells from a polymer acceptor additive

“…The power conversion efficiencies (PCEs) of over 16% have been reported for non-fullerene OSCs based on donor polymers [9][10][11] . Despite the great achievements in improving efficiency, commercialization of large-scale OSCs is limited due to their relatively low environmental stability 8,[12][13][14][15][16] . Of note is that many environmental issues (e.g., heat, oxygen, light, and humidity) have been identified as main factors of device degradation 17 .…”

“…These reported results suggest that the thermal instability of BHJ blends severely limit their outdoor applications, as these devices operating under standard conditions are obviously heated by prolonged illumination of sunlight 27,28 , and the operating temperature for solar panels can be as high as 50-70°C, even reaching 100°C in some areas 29 . Although annealing effects have been extensively and deeply explored in OSCs 12, [14][15][16]24,29,30 , their device efficiencies have been temperature dependent, and cannot withstand temperatures well over 120°C for extended periods of time.…”

“…Several effective approaches such as suitably reducing the crystallinity of photovoltaic polymers 31,32 or fullerenes 24,33 , selecting suitable D/A pairs 34,35 , incorporating a "molecular lock" 16,36 , and cross-linking between D/A components in the active layers have been developed to solve thermal instability of BHJ blends 22,37,38 . Among them, blending host-active layers with additives emerges as a simple and general approach to achieve the optimal blend morphology, and also improves the electronic performance and environmental stability in OSCs [39][40][41] .…”

Self‐Assembly of Chiral‐at‐End Diketopyrrolopyrroles: Symmetry Dependent Solution and Film Optical Activity and Photovoltaic Performance

“…[18] In contrastt oo ther parameters, such as redox and optical characteristics, the molecular order in the active layer remains hard to control.I na ddition to p-p stacking of chromophores, currents trategies to improve device performance targeting molecular arrangementu tiliseh ydrogen bonding, [19][20][21] dipolar interactions [22] and other supramolecular approaches. [23][24][25] The goal of this work is to prepares mall molecule chiral materials of different symmetries that have well defined structures that can be probed precisely spectroscopically,a nd with potentialf or use in OPVs. It is hopedt hat the lessons learned from these materials will ultimately lead to improvedd evice performance through symmetry controlled stereoselectives elf-assembly.…”

Synthesis of the diketopyrrolopyrrole/terpyridine substituted carbazole derivative based polythiophenes for photovoltaic cells

“…Because of their light weight, low cost, and exibility, p-conjugated polythiophenes (PTs) are promising candidates for various optoelectronic device applications, including polymer light-emitting devices, 1,2 electrochromic devices, 3 organic eldeffect transistors, 4,5 photovoltaic (PV) cells, [6][7][8][9][10][11][12][13][14][15] and uorescent chemosensors. [16][17][18][19] Polymer-based photovoltaic cells (PVCs) typically contain a layer comprising a blend of PT and a fullerene derivative.…”