Abstract
Solution-processable small molecules (SMs) that can serve as donors in bulk-heterojunction (BHJ) solar cells are practical alternatives to their polymer counterparts. However, SM-fullerene blends commonly suffer severe voltage losses. In general, devices that reach open-circuit voltages (VOC) > 1 V yield low photocurrents in BHJ solar cells with fullerene acceptors (e.g., PC71BM) and modest power conversion efficiencies (PCEs). In this contribution, we report on the design, synthesis, and BHJ device characteristics of a new SM donor, 2F-DRCN5T, yielding a VOC of up to 1.10 V with PC71BM as the fullerene acceptor, while maintaining PCEs > 7% (over 8% achieved upon solvent-vapor-annealing (SVA) treatment). The negligible energy loss during charge generation (ΔECT), the deep-lying HOMO of 2F-DRCN5T inferred from its large ionization potential (IP), the high charge-transfer-state energy (ECT) of the blend, and a reduced nonradiative voltage loss account for the high VOC achieved in BHJ solar cells.
Original language | English (US) |
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Pages (from-to) | 2717-2722 |
Number of pages | 6 |
Journal | ACS Applied Energy Materials |
Volume | 2 |
Issue number | 4 |
DOIs | |
State | Published - Apr 22 2019 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Chemical Engineering (miscellaneous)
- Energy Engineering and Power Technology
- Electrochemistry
- Materials Chemistry
- Electrical and Electronic Engineering
Keywords
- fluorination
- high open-circuit voltage
- low energy loss
- oligothiophene
- organic photovoltaics
- small-molecule donor