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Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

Zhong Y, Trinh MT, Chen R, Purdum GE, Khlyabich PP, Sezen M, Oh S, Zhu H, Fowler B, Zhang B, Wang W, Nam CY, Sfeir MY, Black CT, Steigerwald ML, Loo YL, Ng F, Zhu XY, Nuckolls C - Nat Commun (2015)

Bottom Line: None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells.We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions.This study describes a new motif for designing highly efficient acceptors for organic solar cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA.

ABSTRACT
Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

No MeSH data available.


Related in: MedlinePlus

Film morphology of PTB7-Th: hPDI3 blend film.(a) Top surface phase image of BHJ thin film measured in tapping mode. (b) Internal phase image of blended thin film measured in tapping mode. (c) Internal DMT (Derjaguin, Muller, Toropov) modulus image of blended thin film measured in peak force quantitative nanomechanical (QNM) mode. Bottom graph is line-cut analysis of image. (c,d) DMT modulus of PTB7-Th and hPDI3 pure thin films and PTB7-Th:hPDI3 blend film. Scale bar, 100 nm (a–c).
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f4: Film morphology of PTB7-Th: hPDI3 blend film.(a) Top surface phase image of BHJ thin film measured in tapping mode. (b) Internal phase image of blended thin film measured in tapping mode. (c) Internal DMT (Derjaguin, Muller, Toropov) modulus image of blended thin film measured in peak force quantitative nanomechanical (QNM) mode. Bottom graph is line-cut analysis of image. (c,d) DMT modulus of PTB7-Th and hPDI3 pure thin films and PTB7-Th:hPDI3 blend film. Scale bar, 100 nm (a–c).

Mentions: We investigated the PTB7-Th:hPDI3-blended film morphology using both tapping mode and quantitative nanomechanical mode41 atomic force microscopy (AFM) (Fig. 4). Although the height image of the top film surface is very smooth (root-mean-squared (RMS) roughness of 0.58 nm), the phase image shows evidence of a distinct phase separation, with domain size of ∼10–20 nm (Fig. 4a and Supplementary Fig. 23). We used an oxygen plasma to remove ∼30 nm of material from the top surface to investigate the blend's internal morphology414243. Here, the phase image clearly shows a continuous interpenetrating network with a feature size in the range of 20–40 nm (Fig. 4b)—a morphology clearly favourable for exciton dissociation and charge transport. Nanomechanical measurements show that the continuous network (dark regions in Fig. 4b) has a DMT (Derjaguin, Muller, Toropov) modulus of ∼2.2 GPa, which is similar to that of the pure film of hPDI3 (details about DMT model in Supplementary Note 6). However, the isolated embedded in the continuous network domains (bright regions in Fig. 4b) have a smaller DMT modulus (∼1.5 GPa), closer to that of a pure PTB7-Th film (Fig. 4c,d). These results suggest an active layer composed of an interpenetrating network of hPDI3-rich domains, embedded in PTB7-Th-rich matrix. Our blend films share very similar morphology to that of PTB7:PC71BM, which is considered an optimal morphology to enable efficient charge generation and transport in BHJ solar cells.41


Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

Zhong Y, Trinh MT, Chen R, Purdum GE, Khlyabich PP, Sezen M, Oh S, Zhu H, Fowler B, Zhang B, Wang W, Nam CY, Sfeir MY, Black CT, Steigerwald ML, Loo YL, Ng F, Zhu XY, Nuckolls C - Nat Commun (2015)

Film morphology of PTB7-Th: hPDI3 blend film.(a) Top surface phase image of BHJ thin film measured in tapping mode. (b) Internal phase image of blended thin film measured in tapping mode. (c) Internal DMT (Derjaguin, Muller, Toropov) modulus image of blended thin film measured in peak force quantitative nanomechanical (QNM) mode. Bottom graph is line-cut analysis of image. (c,d) DMT modulus of PTB7-Th and hPDI3 pure thin films and PTB7-Th:hPDI3 blend film. Scale bar, 100 nm (a–c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595599&req=5

f4: Film morphology of PTB7-Th: hPDI3 blend film.(a) Top surface phase image of BHJ thin film measured in tapping mode. (b) Internal phase image of blended thin film measured in tapping mode. (c) Internal DMT (Derjaguin, Muller, Toropov) modulus image of blended thin film measured in peak force quantitative nanomechanical (QNM) mode. Bottom graph is line-cut analysis of image. (c,d) DMT modulus of PTB7-Th and hPDI3 pure thin films and PTB7-Th:hPDI3 blend film. Scale bar, 100 nm (a–c).
Mentions: We investigated the PTB7-Th:hPDI3-blended film morphology using both tapping mode and quantitative nanomechanical mode41 atomic force microscopy (AFM) (Fig. 4). Although the height image of the top film surface is very smooth (root-mean-squared (RMS) roughness of 0.58 nm), the phase image shows evidence of a distinct phase separation, with domain size of ∼10–20 nm (Fig. 4a and Supplementary Fig. 23). We used an oxygen plasma to remove ∼30 nm of material from the top surface to investigate the blend's internal morphology414243. Here, the phase image clearly shows a continuous interpenetrating network with a feature size in the range of 20–40 nm (Fig. 4b)—a morphology clearly favourable for exciton dissociation and charge transport. Nanomechanical measurements show that the continuous network (dark regions in Fig. 4b) has a DMT (Derjaguin, Muller, Toropov) modulus of ∼2.2 GPa, which is similar to that of the pure film of hPDI3 (details about DMT model in Supplementary Note 6). However, the isolated embedded in the continuous network domains (bright regions in Fig. 4b) have a smaller DMT modulus (∼1.5 GPa), closer to that of a pure PTB7-Th film (Fig. 4c,d). These results suggest an active layer composed of an interpenetrating network of hPDI3-rich domains, embedded in PTB7-Th-rich matrix. Our blend films share very similar morphology to that of PTB7:PC71BM, which is considered an optimal morphology to enable efficient charge generation and transport in BHJ solar cells.41

Bottom Line: None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells.We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions.This study describes a new motif for designing highly efficient acceptors for organic solar cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Columbia University, 3000 Broadway, Havemeyer Hall, MC3130, New York, New York 10027, USA.

ABSTRACT
Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

No MeSH data available.


Related in: MedlinePlus