Effect of Crystallization on the Electronic Energy Levels and Thin Film Morphology of P3HT:PCBM Blends

Tsoi, Wing Chung; Spencer, Steve J.; Yang, Li; Ballantyne, Amy M.; Nicholson, Patrick G.; Turnbull, A.; Shard, Alexander G.; Murphy, Craig E.; Bradley, Donal D. C.; Nelson, Jenny; Kim, Jinhyun

doi:10.1021/ma102841e

Cited by 241 publications

(230 citation statements)

References 39 publications

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“…The volume fraction of PCPDTBT at the top layer of the blend films compared to a pure PCPDTBT top layer is shown in Table 3. Previous studies of polymer-fullerene blends have used these two ratios to correlate the relative polymer concentration at the top surface of the blend [16,17].…”

Section: Effect Of Odt Inclusion On the Compositional Change Of The Amentioning

confidence: 99%

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

Kettle

Waters

Ding

et al. 2015

Solar Energy Materials and Solar Cells

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Section: Effect Of Odt Inclusion On the Compositional Change Of The Amentioning

confidence: 99%

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

Kettle

Waters

Ding

et al. 2015

Solar Energy Materials and Solar Cells

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“…[14][15][16][17][18] This driving force will also be infl uenced by the density of states, [ 19 ] by the local (nano)morphology [20][21][22] and in some cases by the excitation energy [ 23 , 24 ] and by the local electrostatic fi eld. [ 25 , 26 ] Charge collection is infl uenced by (nano)morphology close to the donoracceptor interface, [ 27 ] by the degree of ordering (and hence mobility) in the electron and hole transporting phases, [ 20 , 21 , 28-30 ] by the degree of phase segregation in the binary blend [ 8 , 31 ] and the carrier mobility in the respective phases.…”

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

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134

140

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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.

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“…56 Recent results state a rise only of the HOMO energy level and no change of the LUMO level through chain ordering. 57 For a possible photovoltaic application, we compared RR-P3HT:Si-ncs BHJs with aggRR-P3HT/poly-Si PHJs. The polaron yield is higher and their lifetime is slightly longer in aggRR-P3HT/poly-Si PHJ than in RR-P3HT:Si-ncs BHJ as becomes evident through comparison of the TA spectra in Figure 5a,c.…”

Section: Articlementioning

confidence: 99%

Role of Structural Order and Excess Energy on Ultrafast Free Charge Generation in Hybrid Polythiophene/Si Photovoltaics Probed in Real Time by Near-Infrared Broadband Transient Absorption

et al. 2011

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Despite the central role of light absorption and the subsequent generation of free charge carriers in organic and hybrid organicÀinorganic photovoltaics, the precise process of this initial photoconversion is still debated. We employ a novel broadband (UVÀVisÀNIR) transient absorption spectroscopy setup to probe charge generation and recombination in the thin films of the recently suggested hybrid material combination poly(3-hexylthiophene)/silicon (P3HT/Si) with 40 fs time resolution. Our approach allows for monitoring the time evolution of the relevant transient species under various excitation intensities and excitation wavelengths. Both in regioregular (RR) and regiorandom (RRa) P3HT, we observe an instant (<40 fs) creation of singlet excitons, which subsequently dissociate to form polarons in 140 fs. The quantum yield of polaron formation through dissociation of delocalized excitons is significantly enhanced by adding Si as an electron acceptor, revealing ultrafast electron transfer from P3HT to Si. P3HT/Si films with aggregated RR-P3HT are found to provide free charge carriers in planar as well as in bulk heterojunctions, and losses are due to nongeminate recombination. In contrast for RRa-P3HT/Si, geminate recombination of bound carriers is observed as the dominant loss mechanism. Site-selective excitation by variation of pump wavelength uncovers an energy transfer from P3HT coils to aggregates with a 1/e transfer time of 3 ps and reveals a factor of 2 more efficient polaron formation using aggregated RR-P3HT compared to disordered RRa-P3HT. Therefore, we find that polymer structural order rather than excess energy is the key criterion for free charge generation in hybrid P3HT/Si solar cells.

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Effect of Crystallization on the Electronic Energy Levels and Thin Film Morphology of P3HT:PCBM Blends

Cited by 241 publications

References 39 publications

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

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

Role of Structural Order and Excess Energy on Ultrafast Free Charge Generation in Hybrid Polythiophene/Si Photovoltaics Probed in Real Time by Near-Infrared Broadband Transient Absorption

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