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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

Transient absorption by standard pump-probe measurements on excitation wavelength at 600 nm for (a) pure PFBT-T20TT, (b) PFBT-T20TT: PC71BM blend (1:4) and inset a zoom of the spectrum at 400 ps time delay.
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f4: Transient absorption by standard pump-probe measurements on excitation wavelength at 600 nm for (a) pure PFBT-T20TT, (b) PFBT-T20TT: PC71BM blend (1:4) and inset a zoom of the spectrum at 400 ps time delay.

Mentions: Correlating the charge-separation mechanism and nanoscale molecular packing of the organic BHJ solar cells could facilitate optimization of their overall efficiency414243. In order to understand how the intercalation of PC71BM between the PFBT-T20TT backbones affects the charge generation process, we performed ultrafast transient absorption (TA) spectroscopy measurements. Figure 4 (a) shows the TA spectra of a pure PFBT-T20TT film upon excitation at 600 nm. A broader and positive fractional transmission signal (ΔT/T) is found from 530 nm to 800 nm and is mainly attributed to photobleaching (PB) and stimulated emission (SE) with probably some overlap with a stimulated emission band at longer wavelengths. A red shift of the band can be noticed in the first ten ps which may be related to exciton diffusion to lower energy states (see dynamics in the Figure S4, Supplementary Information). Also two negative bands appear upon photoexcitation at wavelengths, λ < 530 nm (PA1) and λ > 800 nm (PA2). The latter, though broad, is centering around 1050 nm. All bands exhibit virtually the same decay dynamics (Figure S4, Supplementary Information) thus suggesting that they are all related to the transitions from the first excited singlet state.


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)

Transient absorption by standard pump-probe measurements on excitation wavelength at 600 nm for (a) pure PFBT-T20TT, (b) PFBT-T20TT: PC71BM blend (1:4) and inset a zoom of the spectrum at 400 ps time delay.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Transient absorption by standard pump-probe measurements on excitation wavelength at 600 nm for (a) pure PFBT-T20TT, (b) PFBT-T20TT: PC71BM blend (1:4) and inset a zoom of the spectrum at 400 ps time delay.
Mentions: Correlating the charge-separation mechanism and nanoscale molecular packing of the organic BHJ solar cells could facilitate optimization of their overall efficiency414243. In order to understand how the intercalation of PC71BM between the PFBT-T20TT backbones affects the charge generation process, we performed ultrafast transient absorption (TA) spectroscopy measurements. Figure 4 (a) shows the TA spectra of a pure PFBT-T20TT film upon excitation at 600 nm. A broader and positive fractional transmission signal (ΔT/T) is found from 530 nm to 800 nm and is mainly attributed to photobleaching (PB) and stimulated emission (SE) with probably some overlap with a stimulated emission band at longer wavelengths. A red shift of the band can be noticed in the first ten ps which may be related to exciton diffusion to lower energy states (see dynamics in the Figure S4, Supplementary Information). Also two negative bands appear upon photoexcitation at wavelengths, λ < 530 nm (PA1) and λ > 800 nm (PA2). The latter, though broad, is centering around 1050 nm. All bands exhibit virtually the same decay dynamics (Figure S4, Supplementary Information) thus suggesting that they are all related to the transitions from the first excited singlet state.

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