Effect of Carbon Chain Length in the Substituent of PCBM‐like Molecules on Their Photovoltaic Properties

Abstract

A series of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)‐like fullerene derivatives with the butyl chain in PCBM changing from 3 to 7 carbon atoms, respectively (F1–F5), are designed and synthesized to investigate the relationship between photovoltaic properties and the molecular structure of fullerene derivative acceptors. F2 with a butyl chain is PCBM itself for comparison. Electrochemical, optical, electron mobility, morphology, and photovoltaic properties of the molecules are characterized, and the effect of the alkyl chain length on their properties is investigated. Although there is little difference in the absorption spectra and LUMO energy levels of F1–F5, an interesting effect of the alkyl chain length on the photovoltaic properties is observed. For the polymer solar cells (PSCs) based on P3HT as donor and F1–F5, respectively, as acceptors, the photovoltaic behavior of the P3HT/F1 and P3HT/F4 systems are similar to or a little better than that of the P3HT/PCBM device with power conversion efficiencies (PCEs) above 3.5%, while the performances of P3HT/F3 and P3HT/F5‐based solar cells are poorer, with PCE values below 3.0%. The phenomenon is explained by the effect of the alkyl chain length on the absorption spectra, fluorescence quenching degree, electron mobility, and morphology of the P3HT/F1–F5 (1:1, w/w) blend films.

Morphological Stabilization by In Situ Polymerization of Fullerene Derivatives Leading to Efficient, Thermally Stable Organic Photovoltaics

“…The optical and photoluminescent properties of the PCBM:P3HT, PCBSD651, PCBS651, and PCBS211 blends were studied before and after thermal heating at 150 ° C for 25 h. The absorption and emission spectra of the PCBSD651, PCBS651, and PCBS211 blends are essentially unchanged after thermal heating ( Figure 8 and Figure 9 ); they exhibit absorption peaks at 515, 550, and 610 nm due to the extensive π − π stacking along the P3HT backbone (Figure 8 ). [ 20 ] These results suggest that the polymerization between the PCBSD or PCBS molecules in the blends effectively preserves the morphology of the stacking of P3HT and thus maintains the P3HT absorption and emission properties. However, after 25 h heating, the intensity of the P3HT:PCBM blend in the P3HT absorption region is enhanced, which is again indicative of a higher degree of P3HT crystallization.…”

Phase behavior of blends of PCBM with amorphous polymers with different aromaticity

“…1,2 However, C 60 is insoluble or only poorly soluble in most common organic solvents, and only poorly miscible in conjugated polymer matrices, limiting its ability to be incorporated in commercial products. An important breakthrough in polymer photovoltaic devices was achieved when pristine fullerene C 60 was replaced by its highly soluble derivative [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM). 3 At present, there is a race to develop novel conjugated polymers (electron donors) that can further improve the efficiency of polymer solar cells.…”

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ABSTRACT:The phase behavior of [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) blends with amorphous polymers with different degrees of aromaticity has been investigated by differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS). The polymers investigated are the homologous series of polystyrene (PS), poly(2-vinyl-naphthalene) (P2VN), and poly(9-vinyl-phenanthrene) (P9VPh).

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Design and synthesis of soluble dibenzosuberane-substituted fullerene derivatives for bulk-heterojunction polymer solar cells

“…As electron acceptor, conventional PCBM has some well-known drawbacks, such as weak absorption in the visible region and a low-lying LUMO (Lowest Unoccupied Molecular Orbital) energy level, leading to significant loss of open circuit voltage (V oc ). To address the question, numerous PCBM-like fullerene derivatives have been studied as electron acceptors [17][18][19][20][21][22][23][24][25][26], most of which, however, showed poor or just comparable performance to PCBM. Recently, the development of fullerene bis-adduct acceptors for higher V oc PSCs has received considerable attention [27][28][29][30][31][32][33][34][35].…”