Breaking the Voltage-Loss Bottleneck in Organic Photovoltaics via Interfacial Molecular Orientation Engineering.
basic_science · Level V
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- Record sourced from PubMed, PMID 42227991.
- Also identified by DOI 10.1002/adma.73473.
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Abstract
Benefiting from non-fullerene acceptors, organic photovoltaics (OPVs) have achieved power conversion efficiencies exceeding 21%. However, further progress critically depends on suppressing voltage losses (V<sub>loss</sub>), particularly non-radiative voltage losses (ΔV<sub>3</sub>). Here, we employ a precisely controlled donor/acceptor bilayer system, fabricated via a polydimethylsiloxane (PDMS) film-transfer method, to systematically investigate the intrinsic role of interfacial molecular orientation in governing V<sub>loss</sub>. Devices with a face-on/face-on (P5TCN-F0/Y6) configuration exhibit markedly reduced ΔV<sub>3</sub> and overall V<sub>loss</sub> compared with edge-on/face-on (P5TCN-F50/Y6), face-on/edge-on (P5TCN-F0/BTP-2T), and edge-on/edge-on (P5TCN-F50/BTP-2T) counterparts. Transient absorption spectroscopy and time-resolved photoluminescence measurements reveal that the face-on/face-on interface enables efficient charge transfer while suppressing charge-transfer (CT) states recombination. Quantitative analysis further demonstrates that the markedly reduced non-radiative recombination rate of the CT states is responsible for the enhanced electroluminescence quantum efficiency and the reduced ΔV<sub>3</sub> and V<sub>loss</sub>. These findings establish interfacial molecular orientation as a key lever for minimizing ΔV<sub>3</sub> without compromising high photocurrent and provide material design principles and morphology control requirements for further breaking the performance bottleneck in bulk heterojunction OPVs.