New C₈₄ Derivative and Its Application in a Bulk Heterojunction Solar Cell

Abstract

We report here the synthesis and characteristics of a new C 84 adduct ([84]PCBM), realized via a diazoalkane addition reaction. [84]PCBM was obtained as a mixture containing three major isomers.[84]PCBM was tested in a fullerene/poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene) (MDMO-PPV) bulk heterojunction solar cell as the first C 84 derivative to be applied in device fabrication. Spin coating the active layer blend from 1-chloronaphthalene (the very best fullerene solvent) instead of ortho-dichlorobenzene was necessary to obtain the more efficient photovoltaic device. The PV results indicate that the hole mobility of MDMO-PPV may not be increased upon blending with [84]PCBM. This explains the relatively low I SC of the device as due to the buildup of space charge. The V OC of the device is ∼500 mV lower than that of the one with [60]PCBM, while [84]PCBM has a 350 mV higher electron affinity than [60]PCBM. This loss surpasses the linear relation between the donor HOMOacceptor LUMO energy gap and the V OC in this type of device. A maximum power conversion efficiency of 0.25% was reached for the MDMO-PPV:[84]PCBM cells.

Identifying a Threshold Impurity Level for Organic Solar Cells: Enhanced First‐Order Recombination Via Well‐Defined PC84BM Traps in Organic Bulk Heterojunction Solar Cells

“…The LUMO level of PC 84 BM is 0.35 eV lower than that of PC 60 BM (4.3 eV), [ 23 ] as shown in Figure 1 a. In the dilute concentrations used in this study, 0.01%, 0.1%, and 1% (and possibly even 10%) by weight, the PC 84 BM molecule is expected to function as a localized electron trap within the fullerene component of the BHJ material, pictured in Figure 1 b.…”

“…In the dilute concentrations used in this study, 0.01%, 0.1%, and 1% (and possibly even 10%) by weight, the PC 84 BM molecule is expected to function as a localized electron trap within the fullerene component of the BHJ material, pictured in Figure 1 b. The structure of PC 60 BM and the likely confi guration of the d2 isomer of PC 84 BM [ 23 ] are included in the Figure 1 b legend.…”

“…Use of polymers or other small molecules as the electron-accepting material have not yet been as successful. [ 21 , 22 ] [6,6]-phenyl-C 84 -butyric acid methyl ester (PC 84 BM) became briefl y interesting as a solar cell acceptor [ 23 ] due to its strong, broad absorption, and relatively high mobility. [ 24 ] However, it was abandoned as an acceptor due to observed loss of photocurrent and increased recombination.…”

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

“…26 This means that they do not significantly contribute to device photocurrent, limiting the Jsc available for a given active layer thickness. Soluble analogues of the less symmetrical higher fullerenes, such as C 70 (PC 71 BM) 26 and C 84 (PC 85 BM), 27 which absorb better in the visible have been developed to overcome this. The high electron affinity of PC 84 BM results in low device V oc , but PC 71 BM has proven to be a highly effective material, combining similar LUMO energy, electron mobility, solubility and crystallinity to PC 61 BM, but higher optical absorption in the visible as a result of its lower symmetry.…”

Design issues for improved environmental performance of dye-sensitized and organic nanoparticulate solar cells

“…A variety of suggestions have been made to increase the oxidation resistance, and the chemical and morphological stability of polymers which in turn may extend the service life of solar cells, including more rigid structures, cross-linking of polymer chains, the use of p-n block polymers and the use of a variety of conjugated polymers, e.g. [9,66]. So far there are no evaluations of the life cycle environmental impacts of such polymers, which may confer improved stability.…”