Diarylfluorene-Modified Fulleropyrrolidine Acceptors to Tune Aggregate Morphology for Solution-Processable Polymer/Fullerene Bulk-Heterojunction Solar Cells

Abstract

A series of n-type fulleropyrrolidine derivatives as the acceptors, including Th-C60, PFTh-C60, and OPFTh-C60, have been synthesized via the key step of the typical Prato reaction to investigate the steric hindrance effect of various phenylfluorenyl moieties on the electronic structures, aggregate morphologies, and device performances of solar cells. Conjugation-interrupted linkage obviously does not change the energy bandgaps and lowest unoccupied molecular orbital (LUMO) energy levels in PFTh-C60 and OPFTh-C60 models with respect to that of precursor Th-C60 according to UV–vis spectra and cyclic voltammetry. In contrast, dramatically different phase separation behaviors in the bulk heterojunction (BHJ) film blending with poly­(3-hexylthiophene) (P3HT) were observed by atomic force microscopy. A prototype OPFTh-C60-based BHJ polymer solar cell (PSC) with the configuration of ITO/PEDOT:PSS/P3HT:OPFTh-C60 (1:1) (200 nm)/Ca/Al has the performance with the short-circuit current (I sc) of 8.68 mA/cm2, open-circuit voltage (V oc) of 0.63 V, fill factor of 0.51, and power conversion efficiency of 2.80%, better than that in PFTh-C60 or Th-C60-based counterpart devices. Our results indicate that high-performance solar cells can be achieved by the morphology control of active thin films. Diarylfluorene-modified C60 derivatives are promising n-type organic semiconductors for their applications in BHJ PSCs.

Design and synthesis of indole-substituted fullerene derivatives with different side groups for organic photovoltaic devices

“…6B and C). As shown in Tables 2 and 3, before the inverted devices were annealed, the changing trend of Voc was as same as that of the LUMO levels, which showed that the Voc was related to the difference between the HOMO level of the p-type polymer and the LUMO level of the ntype fullerene derivatives [27][28][29]. In the cases of OIHC60P and OIMC60P, the Voc values decreased after the devices were annealed in air, which was probably because the annealing treatment induced the phase separation increasing ( Fig.…”

“…Furthermore, the addition of different substitute group on pyrrolidine ring did not induce significant changes of the energy band gap, which was due to the conjugation-interrupted linkage of the substitute group on fulleropyrrolidine ring [29]. Fig.…”

“…One way is to go beyond PCBM and construct other fullerene derivatives such as indene substituted fullerene derivatives [22], fulleropyrrolidine derivatives [23,24], indolinone-substituted methanofullerene [25], and di(4-methyl-phenyl)methanofullerene bis-adduct [26]. The other strategy is to optimize the substitute groups such as changing aromatic units or alkyl chain length [27][28][29]. For example, the modification of the side group of PCBM significantly affects its solubility and morphology in poly(3-hexylthiophene)(P3HT)/fullerene derivatives blend films, which leads to various photovoltaic performance of organic solar cells [30,31].…”

Fluorene-based macromolecular nanostructures and nanomaterials for organic (opto)electronics

“…The multi-levelled molecular substructures of PF derivatives, such as dialkylfluorenes (F-I), heterofluorenes (F-II) [32][33][34], fused or curved fluorenes (F-III) [35], diarylfluorenes (F-IV) [36,37] and spirofluorenes (F-V) [38,39] (figure 1), have become an ideal platform to demonstrate the four-element principle that contains the p-n covalent design (also called the D-A design) [40][41][42][43], steric design [44,45], conformation and topology design [15,[46][47][48] and supramolecular interaction [25,31,49,50]. Previously, many efforts have been made to clarify low-energy green emission bands (also called g-bands) in PF-based electroluminescent thin films for application in high-performance devices [86].…”

Diarylfluorene‐Based Shape‐Persistent Organic Nanomolecular Frameworks via Iterative Friedel‐Crafts Protocol toward Multicomponent Organic Semiconductors

“…Hyperbranched conjugationinterrupted polymers have been made by means of Friedel-Crafts polymerization [26,27]. More recently, morphologydirected molecular designs have been demonstrated using diarylfluorene-modified fullerenes for bulk heterojunction solar cells by our group [28]. Series of works from XIE-HUANG group demonstrate that this approach is effective for function-directed semiconducting materials in organic electronics.…”