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Title: Mixed Domains Enhance Charge Generation and Extraction in Bulk-Heterojunction Solar Cells with Small-Molecule Donors

Journal Article · · Advanced Energy Materials
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  1. Washington State Univ., Pullman, WA (United States). Dept. Physics and Astronomy
  2. King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudia Arabia). KAUST Solar Center, Physical Sciences and Engineering Division, Material Science and Engineering Program
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  4. Univ. of Potsdam, Postsdam (Germany). Inst. fur Physik und Astronomie, Physik weicher Materie
  5. Univ. of Queensland, Brisbane (Australia). Centre for Organic Photonics & Electronics
  6. King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudia Arabia). KAUST Solar Center, Physical Sciences and Engineering Division (PSE), Chemical Sciences Program
  7. King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudia Arabia). KAUST Solar Center, Physical Sciences and Engineering Division (PSE), Chemical Sciences Program; King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudia Arabia). KAUST Solar Center, Physical Sciences and Engineering Division, Material Science and Engineering Program
+ Show Author Affiliations

Abstract The interplay between nanomorphology and efficiency of polymer‐fullerene bulk‐heterojunction (BHJ) solar cells has been the subject of intense research, but the generality of these concepts for small‐molecule (SM) BHJs remains unclear. Here, the relation between performance; charge generation, recombination, and extraction dynamics; and nanomorphology achievable with two SM donors benzo[1,2‐ b :4,5‐ b ]dithiophene‐pyrido[3,4‐ b ]‐pyrazine BDT(PPTh 2 ) 2 , namely SM1 and SM2, differing by their side‐chains, are examined as a function of solution additive composition. The results show that the additive 1,8‐diiodooctane acts as a plasticizer in the blends, increases domain size, and promotes ordering/crystallinity. Surprisingly, the system with high domain purity (SM1) exhibits both poor exciton harvesting and severe charge trapping, alleviated only slightly with increased crystallinity. In contrast, the system consisting of mixed domains and lower crystallinity (SM2) shows both excellent exciton harvesting and low charge recombination losses. Importantly, the onset of large, pure crystallites in the latter (SM2) system reduces efficiency, pointing to possible differences in the ideal morphologies for SM‐based BHJ solar cells compared with polymer‐fullerene devices. In polymer‐based systems, tie chains between pure polymer crystals establish a continuous charge transport network, whereas SM‐based active layers may in some cases require mixed domains that enable both aggregation and charge percolation to the electrodes.

Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-05CH11231; CRG_R2_13_BEAU_KAUST_1; DP120101372; AC02-76SF00515
OSTI ID:
1462361
Alternate ID(s):
OSTI ID: 1429523
Journal Information:
Advanced Energy Materials, Vol. 8, Issue 19; ISSN 1614-6832
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 40 works
Citation information provided by
Web of Science

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Cited By (7)

Subtle Molecular Tailoring Induces Significant Morphology Optimization Enabling over 16% Efficiency Organic Solar Cells with Efficient Charge Generation journal December 2019
Barrierless Free Charge Generation in the High‐Performance PM6:Y6 Bulk Heterojunction Non‐Fullerene Solar Cell journal January 2020
Miscibility-Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation journal January 2018
Charge and Triplet Exciton Generation in Neat PC 70 BM Films and Hybrid CuSCN:PC 70 BM Solar Cells journal November 2018
Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells journal July 2019
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Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells conference July 2019

Figures / Tables (30)

Figure 1(p. 3)figure Figure 1
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Related Subjects

25 ENERGY STORAGE
36 MATERIALS SCIENCE
Small molecule
organic solar cell
photovoltaic device
charge transport
domain purity
mixed domains
resonant X-ray scattering
microscopy
transient spectroscopy