Fullerene acceptors/derivatives 70 PCBM

Various alternative acceptor components for organic BHJ solar cells have been tried in an attempt to improve cell performance. Fullerene derivatives such as C70 PCBM and Cg4 PCBM have been used in place of Ceo PCBM, because the lower molecular symmetry compared with Ceo PCBM enables stronger light absorption by the fullerene. The C70 PCBM derivatives were relatively successful, leading to 3% power conversion efficiency for devices made with MDMO-PPV polymer (Wienk et al, 2003). The Cg4 derivatives resulted in rather poor device efficiencies, attributed to the unfavourable film morphology resulting from the immiscibility of Cs4 derivatives with typical organic solvents (Kooistra et al, 2006). 

Kietzke et al. have shown for bilayer solar cells based on M3EH-PPV and several acceptor polymers with varying electron affinities and the fullerene derivative PCBM that the open circuit voltage is linearly related to the respective LUMO levels [225]. While CN-PPV-PPE acceptors resulted in an increased open circuit voltage of about 1.5 V, the fill factor and photocurrent were smaller than those for CN-ether-PPV [225]. 

Many new electron acceptor materials have been tested in the polymer BHJ blend system, including polymer polymer blend, polymerrCd, polymer oxide, i etc. However, currently they are not as effective as the polymer PCBM system. To further improve the performance of the promising polymer PF-co-DTB, we work on new fullerene derivative as electron acceptor materials. It is shown up to a large amount of (80wt.%) PCBM is required for optimal performance arising from a strong enhancement of... 

In a heterojunction blend, another important component is acceptor material for electron injection and transport. Most used acceptor materials are fullerene derivatives such as [eOjPCBM, [70]PCBM, etc. In early studies, [60]PCBM was replaced with [70]PCBM to enhance the light absorption because of the more asymmetric structure of [70]PCBM... 

The most commonly nsed Cgo derivative is a methanofullerene called PCBM (l-(3-methoxycarbonyl)-propyl-l-l-(6 6)C6i), which proved to be an excellent electron acceptor in mnltiple bnUc heterojnnction solar cells (Fignre 2.40a). The particular ability of PCBM to mix homogeneously with the other components of the organic active layer placed fullerene derivative at the first place in the rank of the electron acceptors suitable for solar cells. - The C70 analog (PC70BM) was also developed for these pnrposes. ... 

Fullerene derivatives, like mono(l-[3-(methoxycarbonyl) propyl]-l-phenyl)-[6,6]C6i (mono-PCBM, Figure 29(c)) and the higher substituted fullerene derivative bis(l-[3-(methoxy-carbonyl)-propyl]-l-phenyl)-[6,6]Cs2 (bis-PCBM, Figure 29(d)) are frequently used as acceptor materials due to their high electron affinity. The bis-PCBM compound reveals a better solubility toward organic solvents than mono-PCBM and represents, therefore, an interesting new candidate for solution deposition techniques. Furthermore, bis-PCBM shows a higher Lowest... 

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