Developing efficient and stable organic photovoltaics (OPVs) is crucial for the technology's commercial success. However, combining these key attributes remains challenging. Herein, we incorporate the small molecule 2-((3,6-dibromo-9 H -carbazol-9-yl)ethyl)phosphonic acid (Br-2PACz) between the bulk-heterojunction (BHJ) and a 7 nm-thin layer of MoO 3 in inverted OPVs, and study its effects on the cell performance. We find that the Br-2PACz/MoO 3 hole-extraction layer (HEL) boosts the cell's power conversion efficiency (PCE) from 17.36% to 18.73% (uncertified), making them the most efficient inverted OPVs to date. The factors responsible for this improvement include enhanced charge transport, reduced carrier recombination, and favourable vertical phase separation of donor and acceptor components in the BHJ. The Br-2PACz/MoO 3 -based OPVs exhibit higher operational stability under continuous illumination and thermal annealing (80 °C). The T 80 lifetime of OPVs featuring Br-2PACz/MoO 3 – taken as the time over which the cell's PCE reduces to 80% of its initial value – increases compared to MoO 3 -only cells from 297 to 615 h upon illumination and from 731 to 1064 h upon continuous heating. Elemental analysis of the BHJs reveals the enhanced stability to originate from the partially suppressed diffusion of Mo ions into the BHJ and the favourable distribution of the donor and acceptor components induced by the Br-2PACz.
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18.9% Efficient Organic Solar Cells Based on n‐Doped Bulk‐Heterojunction and Halogen‐Substituted Self‐Assembled Monolayers as Hole Extracting Interlayers
The influence of halogen substitutions (F, Cl, Br, and I) on the energy levels of the self‐assembled hole‐extracting molecule [2‐(9
- Award ID(s):
- 1700982
- NSF-PAR ID:
- 10372794
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 12
- Issue:
- 45
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract A unique approach is used to relate the HOMO‐LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X2(X = F, Cl, Br, I), S8and P4. For the dihalogens, the [IP – EA] energies are found to be: F2(12.58 eV), Cl2(8.98 eV), Br2(7.90 eV), I2(6.78 eV). We suggest that the
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