Homologous Self-Assembled Oligomers as Dual Anode/Cathode Interface Layers for Efficient Organic Photovoltaics

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• High-efficiency organic photovoltaics (OPVs) require engineered interfacial layers to tune electrode energetics, suppress recombination, and enforce carrier selectivity.
• Current anode and cathode interface layers (AILs and CILs) utilize distinct chemistries, complicating synthesis and hindering scalability.

Purpose of the Study:

• To develop a versatile molecular platform for generating both AILs and CILs from a single homologous oligomer.
• To simplify the synthesis of interfacial layers for organic photovoltaics (OPVs).
• To improve the power conversion efficiency and stability of OPV devices.

Main Methods:

• Synthesized phosphonate-functionalized CIL (2DPeBcz) and phosphonic-acid-functionalized AIL (2DPaBcz) from a donor-acceptor-donor (carbazole-benzothiadiazole-carbazole) oligomer using a three-step route.
• Utilized self-assembled monolayers for interface modification.
• Incorporated the developed layers into D18:BTP-eC9 OPV devices.

Main Results:

• Achieved a power conversion efficiency of 19.3% in OPV devices incorporating the new AIL and CIL.
• Demonstrated improved storage, light-soaking, and thermal stability of the OPV devices.
• Electrical characterization revealed reduced trap density and balanced carrier mobility.

Conclusions:

• A unified synthetic strategy for AILs and CILs derived from a single molecular backbone simplifies material preparation.
• The versatile structural approach enables scalable, high-performance OPV interfaces with enhanced device stability.
• This work presents a significant advancement in OPV interface engineering.