Proceedings Article | 1 October 2023
KEYWORDS: Solar cells, Organic photovoltaics, Crystallography, Solar energy, Spectroscopy, Solid state electronics, Polymers, Photovoltaics, Imaging spectroscopy, X-rays
Organic semiconductors have garnered interest in wide range of applications including photovoltaics, light emission, photodetectors, sensors, and photocatalysis. Specifically, the emerging organic photovoltaics (OPVs) make use of donor-acceptor conjugated polymers in a bulk heterojunction (BHJ) morphology. Focused continued efforts in developing donor polymers and non-fullerene acceptors enabled the power conversion efficiency (PCEs) of single-junction solar cells over 19% today.[1,2] With the aim of further improving PCEs and stability of OPVs, efforts have been expended on understanding structure-processing-stability-property interrelations, which necessitates molecular-level understanding of thin film morphology of the photoactive layer, contact layers and interfaces between them. Here we provide a method to resolve structure-property relationships in OPVs using multiscale characterization and device physics including charge generation, extraction and recombination processes.[3] Synergism between the X-ray diffraction, solid-state NMR/EPR and modelling techniques enabled the bulk and interfacial morphology in BHJ thin films and contact layers to be resolved and distinguished.[3,4] We will discuss the state-of-the-art 2D NMR and EPR spectroscopy and imaging techniques suitable for resolving thin film morphology in PM6:Y6 solar cells at atomic-scale resolution. In addition, we will demonstrate how a hybrid bottom-up and top-down NMR crystallography approach in conjunction with device physics can be used to establish structure-property relationships in NFA based OPVs.[4,5] Our approach can be further extended to resolve structure-stability-property relationships in high performance organic photodetectors (OPDs) and organic electrochemical transistors (OECTs).
References:
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