Perylenediimide derivatives with branched imide substituents: Aggregation behaviour and impact on photovoltaic properties. (1st November 2022)

• Record Type: Journal Article
• Authors: Bhardwaj, Komal; Naqvi, Samya; Saini, Saurabh K; Kumar, Mahesh; Kumar, Rachana
• Is Part Of: Solar energy. Volume 246(2022)
• Page Start: 320
• Page End: 330
• Publication Date: 2022-11-01
• Subjects: Organic solar cell -- Perylenediimide -- Electron transport -- N-type semiconductor; PDI Perylenediimide -- OPV Organic photovoltaics -- DFT Density functional theory; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2022.10.012
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Perylenediimide (PDI) derivatives bearing branched end groups have been designed and synthesized for their controlled self-assembly formation and tuning of energy levels. On using these PDI derivatives as ETL better solar cell device performance as high as 5.7 (±0.1) % was achieved compared to their precursor PDI molecules with linear/short substituents. Detailed study has been performed for the structure–property relationship for self-assembly behaviour, photophysical and charge transport properties. The device data is studied experimentally as well as theoretically and it is observed that PDI derivatives forming J-type aggregates show better device properties in comparison to H-type aggregates. Abstract: Although organic photovoltaics has witnessed significant growth in their power conversion efficiency still there is need to develop novel electron transport materials that can improve the electron extraction through energy level tuning. Perylenediimide (PDI) is one of the known n-type semiconductor which forms highly ordered self-assembled aggregates by intermolecular interactions. Considering the facile processability of these, herein we report perylenediimide (PDI) derivatives with branched end groups via Michael addition reaction. This work describes the synthesis of two PDI derivatives, i.e., MA-PDI-EDA and MA-PDI-PPD via two-step process and these were further studied for the effect of branched end groups on aggregation behaviour as well as its correlation with the opto-electronic properties. The self-assembling and charge transport properties of the synthesized molecules are fine tuned by branched imide substituent which allows improved performance of these materials as electron transport layer in organic solar cell devices in comparison to their PDI precursors. MA-PDI-EDA forming J-type aggregate showed improved power conversion efficiency in comparison to MA-PDI-PPD undergoing H-type aggregation. Ultrafast transient absorption spectroscopy was also performed for understanding the charge carrier dynamics in the two MA products. A complete rational for the observation is discussed using the theoretical fitting of device I-V characteristics.