PCBM-Based n-Type Semiconductors

Unique chemistry and physics of fullerene (C₆₀) materials continue to stimulate advances in applied and fundamental science. Fullerenes are known as excellent electron acceptors and can be chemically modified to improve solubility in organic solvents. Such soluble fullerene derivatives are known as some of the best n-type organic semiconductors¹. Moreover, molecular heterojunctions made by covalently linking fullerenes with electron donating or photoactive macromolecules show promise as intrinsic p/n-type semiconductors and even artificial mimics of biological photosynthesis.² To help our customers achieve their research breakthroughs in organic electronics, we are pleased to offer a line of high quality functionalized fullerene products.

Methanofullerene Phenyl-C61-Butyric-Acid-Methyl-Ester ([60]PCBM) is an effective solution processable n-type organic semiconductor. It can be blended with p-type conjugated polymers to make photovoltaic (PV) cells^3,4 and thin-film organic field effect transistors (OFETs),⁵ and has also shown promise for use in photodectors.⁶ [60]PCBM is soluble in the same organic solvents as excellent p-type semiconductors such as: MDMO-PPV, MEH-PPV and P3HT (Table 1). This simplifies the preparation of blends and solution processing of heterojuction PV cells and OFETs. The high affinity of PCBM results is efficient photo-induced electron transfer from p-type polymers as well as from metal electrodes in biased thin-film OFETs.⁷ Power conversion efficiencies of up to ~4.4% have been reported for bulk heterojunction PV cells made with [60]PCBM.⁸

Table 1 Conduction (LUMO) and valence (HOMO) band energies of p- and n-type organic semiconductors available in our catalog

Organic Semiconductor	Product No.	LUMO	HOMO	Soluble in:
MDMO-PPV p-type	546461	-2.8eV	-5.0eV	Chloroform Chlorobenzene Dichlorobenzene Toluene
MEH-PPV p-type	541443 (MW 40 – 70 kDa) 541435 (MW 70 – 100 kDa) 536512 (MW 150 – 250 kDa)	-3.2eV	-5.4eV
P3HT p-type	445703 (regioregular) 510823 (regiorandom) 669067 (electronic grade)	-3.3eV	-5.0eV
PCBM n-type	684430	-3.7eV	-6.1eV

The fabrication of thin film organic electronics devices is complex, with slight variations of molecular structures having profound effects on film morphology and charge transport. To help you optimize the performance of your devices, We are pleased to offer a library of PCBMs that includes [60]PCBM analogs based on higher fullerenes (C₇₀ and C₈₄), as well as those derived by chemical alterations of the addend moeiety to vary solubility and electronic properties. Members of the library have shown advantages in different devices and will help you explore and experiment in your research. Different purity grades of [60]PCBM are available for device scale-up, research, and exploratory work (Tables 2 and 3).

Table 2 Our PCBM Library

Prod. No.	Product Name	Structure	Applications
684430	Phenyl-C61-Butyric-Acid-Methyl Ester, [60]PCBM, 99% (scale-up grade)		Best-known PCBM compound. Effective n-type semiconductor soluble in organic solvents. Used for solar cells (OPVs), thin-film transistors (OFETs), and photodetectors.6,10-11
684449	Phenyl-C61-Butyric-Acid-Methyl Ester, [60]PCBM, 99.5% (research grade)
684457	Phenyl-C61-Butyric-Acid-Methyl Ester, [60]PCBM, 99.9% (for exploratory work)
684465	Phenyl-C71-Butyric-Acid-Methyl Ester, [70]PCBM, 99%		[70]PCBM has increased optical absorption in the visible region compared to [60PCBM. This can lead to improved light-harvesting in OPVs,12 especially in combination with large bandgap donors like MDMO-PPV (546461)
685321	Phenyl-C61-Butyric-Acid-Butyl Ester, PCBB, [60]PCB-C4> 97%		PCBB is slightly more soluble than [60]PCBM, resulting in improved film morphology and higher performing OPV devices deposited from certain organic solvents (THF, p-xylene).14
684481	Phenyl-C61-Butyric-Acid-Octyl Ester, PCBO, [60]PCB-C8 , 99%		Highly soluble PCBM suitable for applications as a general electron acceptor and scavenger in organic solvents and blends.
688215	Thienyl-C61-Butyric-Acid-Methyl Ester, [60]ThCBM, 99%		PCBM derivative optimized for optimal blending with polythiophene p-type semiconductors, such as P3HT (669067).15
684503	Pentadeuterophenyl-C61-Butyric-Acid-Methyl Ester, d5-PCBM, 99%		Isotopically labeled PCBM for spectroscopic (e.g. SIMS) studies of film morphology and diffusion in thin-film organic devices.

Table 3 Properties of selected PCBMs

Product	[60]PCBM	[70]PCBM	[84]PCBM	[60]ThCBM
Product Number	684430 684449 684457	684465	684473	688215
First Reduction Potential, E1/2 (V)	-1.078	-1.089	-0.730	-1.08
Solubility (mg/ml) ·toluene ·p-xylene ·chlorobenzene ·chloroform ·o-dichlorobenzene (ODCB)	10 5 25 25 30	20 10 40 30 70		5 5 10 20 20
Molar Extinction Coefficients (mol-1 cm-1) 400 nm 650 nm	4,900 <1,000	19,000 2,000	28,000 4,000

1. Newman CR, Frisbie CD, da Silva Filho DA, Brédas J, Ewbank PC, Mann KR. 2004. Introduction to Organic Thin Film Transistors and Design of n-Channel Organic Semiconductors. Chem. Mater.. 16(23):4436-4451. https://doi.org/10.1021/cm049391x

2. Cravino A, Sariciftci NS. 2002. Double-cable polymers for fullerene based organic optoelectronic applications. J. Mater. Chem.. 12(7):1931-1943. https://doi.org/10.1039/b201558g

3. Coakley KM, McGehee MD. 2004. Conjugated Polymer Photovoltaic Cells. Chem. Mater.. 16(23):4533-4542. https://doi.org/10.1021/cm049654n

4. Thompson BC, Kim Y, Reynolds JR. 2005. Spectral Broadening in MEH-PPV:PCBM-Based Photovoltaic Devices via Blending with a Narrow Band Gap Cyanovinylene?Dioxythiophene Polymer. Macromolecules. 38(13):5359-5362. https://doi.org/10.1021/ma0505934

5. Meijer EJ, de Leeuw DM, Setayesh S, van Veenendaal E, Huisman B-, Blom PWM, Hummelen JC, Scherf U, Klapwijk TM. 2003. Solution-processed ambipolar organic field-effect transistors and inverters. Nature Mater. 2(10):678-682. https://doi.org/10.1038/nmat978

6. Wallace GG, Chen J, Li D, Moulton SE, Razal JM. 2010. Nanostructured carbon electrodes. J. Mater. Chem.. 20(18):3553. https://doi.org/10.1039/b918672g

7. Anthopoulos TD, Tanase C, Setayesh S, Meijer EJ, Hummelen JC, Blom PWM, de Leeuw DM. 2004. Ambipolar Organic Field-Effect Transistors Based on a Solution-Processed Methanofullerene. Adv. Mater.. 16(23-24):2174-2179. https://doi.org/10.1002/adma.200400309

8. Li G, Shrotriya V, Huang J, Yao Y, Moriarty T, Emery K, Yang Y. 2005. High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends. Nature Mater. 4(11):864-868. https://doi.org/10.1038/nmat1500

9. Günes S, Neugebauer H, Sariciftci NS. 2007. Conjugated Polymer-Based Organic Solar Cells. Chem. Rev.. 107(4):1324-1338. https://doi.org/10.1021/cr050149z

10. Wallace GG, Chen J, Li D, Moulton SE, Razal JM. 2010. Nanostructured carbon electrodes. J. Mater. Chem.. 20(18):3553. https://doi.org/10.1039/b918672g

11. Anthopoulos TD, de Leeuw DM, Cantatore E, van ?t Hof P, Alma J, Hummelen JC. 2005. Solution processible organic transistors and circuits based on a C70 methanofullerene. Journal of Applied Physics. 98(5):054503. https://doi.org/10.1063/1.2034083

12. Wienk MM, Kroon JM, Verhees WJH, Knol J, Hummelen JC, van Hal PA, Janssen RAJ. 2003. Efficient Methano[70]fullerene/MDMO-PPV Bulk Heterojunction Photovoltaic Cells. Angew. Chem. Int. Ed.. 42(29):3371-3375. https://doi.org/10.1002/anie.200351647

13. Anthopoulos T, Kooistra F, Wondergem H, Kronholm D, Hummelen J, de?Leeuw D. 2006. Air-Stable n-Channel Organic Transistors Based on a Soluble C84 Fullerene Derivative. Adv. Mater.. 18(13):1679-1684. https://doi.org/10.1002/adma.200600068

14. Zheng L, Zhou Q, Deng X, Yuan M, Yu G, Cao Y. 2004. Methanofullerenes Used as Electron Acceptors in Polymer Photovoltaic Devices. J. Phys. Chem. B. 108(32):11921-11926. https://doi.org/10.1021/jp048890i

15. Popescu LM, van ?t Hof P, Sieval AB, Jonkman HT, Hummelen JC. 2006. Thienyl analog of 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene for bulk heterojunction photovoltaic devices in combination with polythiophenes. Appl. Phys. Lett.. 89(21):213507. https://doi.org/10.1063/1.2397003