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Molecular packing and electronic processes in amorphous-like polymer bulk heterojunction solar cells with fullerene intercalation.

Xiao T, Xu H, Grancini G, Mai J, Petrozza A, Jeng US, Wang Y, Xin X, Lu Y, Choon NS, Xiao H, Ong BS, Lu X, Zhao N - Sci Rep (2014)

Bottom Line: In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c] thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative.Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner.Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Engineering, Chinese University of Hong Kong, New Territories, Hong Kong.

ABSTRACT
The interpenetrating morphology formed by the electron donor and acceptor materials is critical for the performance of polymer:fullerene bulk heterojunction (BHJ) photovoltaic (PV) cells. In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c] thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative. Grazing incidence X-ray scattering measurements reveal the lower-ordered nature of the BHJ system as well as an intermixing morphology with intercalation of fullerene molecules between the PFBT-T20TT lamella. Steady-state and transient photo-induced absorption spectroscopy reveal ultrafast charge transfer (CT) at the PFBT-T20TT/fullerene interface, indicating that the CT process is no longer limited by exciton diffusion. Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner. Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain.

No MeSH data available.


Related in: MedlinePlus

Schematic representation of the proposed weakly-ordered morphology in (a) pure PFBT-T20TT and (b)PFBT-T20TT:PC71BM.Corresponding lamellar spacing for (c) pure polymer and (d) PFBT-T20TT:PC71BM blend together with related charge separation dynamics by electron and hole transfer.
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f3: Schematic representation of the proposed weakly-ordered morphology in (a) pure PFBT-T20TT and (b)PFBT-T20TT:PC71BM.Corresponding lamellar spacing for (c) pure polymer and (d) PFBT-T20TT:PC71BM blend together with related charge separation dynamics by electron and hole transfer.

Mentions: Figure 3 illustrates the schematics of the molecular packing for pure PFBT-T20TT and blends based on the combined GIWAXS and GISAXS results. Despite the lack of strong π-π stacking (Figure S2, Supplementary Information), lamellar stacking is preferentially normal to the substrate in pure PFBT-T20TT thin films as illustrated in Figure 3(a). Blend films are more disordered with no preferential lamellar orientation (Figure S3, Supplementary Information), as evidenced by the ring-like lamellar peak observed in the scattering patterns. The significant shift in the lamellar spacing strongly suggests the intercalation of fullerene derivatives into the PFBT-T20TT domains (Figure 3 (b)). It is likely that the branched side chains attached to PFBT-T20TT backbones provide ample room for the PC71BM molecules. No crystalline PFBT-T20TT domain remains after mixing, as indicated by the scattering data. Note that when increasing the polymer:PCBM ratio from 1:2 to 1:4 the lamella distance of the polymer stays the same, indicating that a constant PCBM fraction in the mixing phase.


Molecular packing and electronic processes in amorphous-like polymer bulk heterojunction solar cells with fullerene intercalation.

Xiao T, Xu H, Grancini G, Mai J, Petrozza A, Jeng US, Wang Y, Xin X, Lu Y, Choon NS, Xiao H, Ong BS, Lu X, Zhao N - Sci Rep (2014)

Schematic representation of the proposed weakly-ordered morphology in (a) pure PFBT-T20TT and (b)PFBT-T20TT:PC71BM.Corresponding lamellar spacing for (c) pure polymer and (d) PFBT-T20TT:PC71BM blend together with related charge separation dynamics by electron and hole transfer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048884&req=5

f3: Schematic representation of the proposed weakly-ordered morphology in (a) pure PFBT-T20TT and (b)PFBT-T20TT:PC71BM.Corresponding lamellar spacing for (c) pure polymer and (d) PFBT-T20TT:PC71BM blend together with related charge separation dynamics by electron and hole transfer.
Mentions: Figure 3 illustrates the schematics of the molecular packing for pure PFBT-T20TT and blends based on the combined GIWAXS and GISAXS results. Despite the lack of strong π-π stacking (Figure S2, Supplementary Information), lamellar stacking is preferentially normal to the substrate in pure PFBT-T20TT thin films as illustrated in Figure 3(a). Blend films are more disordered with no preferential lamellar orientation (Figure S3, Supplementary Information), as evidenced by the ring-like lamellar peak observed in the scattering patterns. The significant shift in the lamellar spacing strongly suggests the intercalation of fullerene derivatives into the PFBT-T20TT domains (Figure 3 (b)). It is likely that the branched side chains attached to PFBT-T20TT backbones provide ample room for the PC71BM molecules. No crystalline PFBT-T20TT domain remains after mixing, as indicated by the scattering data. Note that when increasing the polymer:PCBM ratio from 1:2 to 1:4 the lamella distance of the polymer stays the same, indicating that a constant PCBM fraction in the mixing phase.

Bottom Line: In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c] thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative.Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner.Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic Engineering, Chinese University of Hong Kong, New Territories, Hong Kong.

ABSTRACT
The interpenetrating morphology formed by the electron donor and acceptor materials is critical for the performance of polymer:fullerene bulk heterojunction (BHJ) photovoltaic (PV) cells. In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c] thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative. Grazing incidence X-ray scattering measurements reveal the lower-ordered nature of the BHJ system as well as an intermixing morphology with intercalation of fullerene molecules between the PFBT-T20TT lamella. Steady-state and transient photo-induced absorption spectroscopy reveal ultrafast charge transfer (CT) at the PFBT-T20TT/fullerene interface, indicating that the CT process is no longer limited by exciton diffusion. Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner. Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain.

No MeSH data available.


Related in: MedlinePlus