Charge Transport and Recombination in Low‐Bandgap Bulk Heterojunction Solar Cell using Bis‐adduct Fullerene

Azimi, Hamed; Senes, Alessia; Scharber, Markus C.; Hingerl, Kurt; Brabec, Christoph J.

doi:10.1002/aenm.201100331

Cited by 120 publications

(95 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The value of A s for bis-PCBM is smaller than that for PCBM by 0.3 eV, which indicates that bis-PCBM has a higher LUMO and is a weaker acceptor than PCBM. This result corresponds to previous reports [10][11][12][13]17]. Since V oc increases with raising LUMO levels of C 60 -derivatives [19][20], the present finding suggests a larger V oc of P3HT:bis-PCBM solar cell than that of P3HT:PCBM, as actually observed as 0.15 V increase [10].…”

Section: Resultssupporting

confidence: 93%

See 1 more Smart Citation

Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct

Akaike¹,

Kanai²,

Ouchi³

et al. 2013

Chemical Physics

View full text Add to dashboard Cite

Section: Resultssupporting

confidence: 93%

“…Recently, bis-adduct of PCBM (bis-PCBM, Fig. 1(c)) has been used as an acceptor in bulk heterojunction OPVs [10][11][12][13], which has the two side chains of phenyl-butyric acid methyl ester. V oc is further enhanced by 0.15 V The use of bis-PCBM, Fig.…”

Section: Introductionmentioning

confidence: 99%

Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct

Akaike¹,

Kanai²,

Ouchi³

et al. 2013

Chemical Physics

View full text Add to dashboard Cite

“…[ 35 ] We fi nd high charge collection only at a reverse bias of − 5 V in the blend with bis -PCBM and at − 10 V in the blend with ICBA (Figure 4 b). PCDTBT (Figure 4 c) features a very high short-circuit internal quantum effi ciency with PCBM, [ 58 ] but shows low photocurrent and fi ll factor with both fullerene multiadducts.…”

Section: Full Papermentioning

confidence: 99%

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

Faist

Shoaee

Tuladhar

et al. 2013

Advanced Energy Materials

134

140

View full text Add to dashboard Cite

The use of fullerenes with two or more adducts as acceptors has been recently shown to enhance the performance of bulk‐heterojunction solar cells using poly(3‐hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open‐circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open‐circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multiadducts like bis‐PCBM (bis adduct of Phenyl‐C61‐butyric acid methyl ester) or the indene C60 bis‐adduct ICBA. Here we investigate the reasons for this decrease in photocurrent. We find that it can be attributed partly to a loss in charge generation efficiency that may be related to the LUMO‐LUMO and HOMO‐HOMO (highest occupied molecular orbital) offsets at the donor‐acceptor heterojunction, and partly to reduced charge carrier collection efficiencies. We show that the P3HT exhibits efficient collection due to high hole and electron mobilities with mono‐ and multiadduct fullerenes. In contrast the less crystalline polymer Poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl (PCDTBT) shows inefficient charge carrier collection, assigned to low hole mobility in the polymer and low electron mobility when blended with multiadduct fullerenes.

show abstract

“…Whilst charge mobilities are low in organic semiconductors and collection losses have been shown to limit the fill factor (FF) [3][4][5] and short circuit current density (J SC ) [6][7][8][9][10] of certain devices, low mobilities do not necessarily prevent devices from performing efficiently. However the lower charge mobilities and diffusion coefficients in organic semiconductors do mean that diffusion alone is insufficient for charge carrier collection and drift must account for a large proportion of the generated photocurrent.…”

mentioning

confidence: 99%

Influence of doping on charge carrier collection in normal and inverted geometry polymer:fullerene solar cells

Dibb

Muth

Kirchartz

et al. 2013

Sci Rep

View full text Add to dashboard Cite

While organic semiconductors used in polymer:fullerene photovoltaics are generally not intentionally doped, significant levels of unintentional doping have previously been reported in the literature. Here, we explain the differences in photocurrent collection between standard (transparent anode) and inverted (transparent cathode) low band-gap polymer:fullerene solar cells in terms of unintentional p-type doping. Using capacitance/voltage measurements, we find that the devices exhibit doping levels of order 10 16 cm 23 , resulting in space-charge regions ,100 nm thick at short circuit. As a result, low field regions form in devices thicker than 100 nm. Because more of the light is absorbed in the low field region in standard than in inverted architectures, the losses due to inefficient charge collection are greater in standard architectures. Using optical modelling, we show that the observed trends in photocurrent with device architecture and thickness can be explained if only charge carriers photogenerated in the depletion region contribute to the photocurrent.T he record power conversion efficiency (PCE) achieved by polymer:fullerene solar cells has increased considerably in the past 4 years to a record published value of 9.2% 1 for a single bulk heterojunction and efficiencies of 10.6% for tandem solar cells 2 . This is despite the fact that organic semiconductors are known to be both structurally and electronically disordered, have lower dielectric constants inhibiting separation of the photogenerated excitonic species and have charge carrier mobilities orders of magnitude lower than inorganic semiconductors.Whilst charge mobilities are low in organic semiconductors and collection losses have been shown to limit the fill factor (FF) 3-5 and short circuit current density (J SC ) 6-10 of certain devices, low mobilities do not necessarily prevent devices from performing efficiently. However the lower charge mobilities and diffusion coefficients in organic semiconductors do mean that diffusion alone is insufficient for charge carrier collection and drift must account for a large proportion of the generated photocurrent. Additionally, polymer:fullerene solar cells are not intentionally doped like their inorganic counterparts or like many small molecule solar cells 11 and therefore rely on selective contacts and the difference in work function between electrodes for efficient charge collection. However, several studies have found evidence for unintentional doping [12][13][14][15][16][17][18][19] and discussed the consequences for device behaviour 6,[20][21][22][23][24][25][26][27][28][29][30] . Whilst the origin of this doping is unclear 15 , its effects on photovoltaic performance can be substantial; however many recent analyses of device performance neglect doping 8,[31][32][33] despite the fact that the influence of doping and the electric field on charge carrier collection is well known for a long time 34 and wellstudied for instance in the field of quantum dot photovoltaics 35,36 .In this paper, we address the...

show abstract

Charge Transport and Recombination in Low‐Bandgap Bulk Heterojunction Solar Cell using Bis‐adduct Fullerene

Cited by 120 publications

References 32 publications

Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct

Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

Influence of doping on charge carrier collection in normal and inverted geometry polymer:fullerene solar cells

Contact Info

Product

Resources

About