Performance improvement of large-area roll-to-roll slot-die-coated inverted polymer solar cell by tailoring electron transport layer

Abstract

For attaining the commercialization, the large-area roll-to-roll (R2R) slot-die-coated inverted polymer solar cells (PSCs) would be promising. The electron transport layer (ETL) plays an important role in scale-up development from small PSCs. In this work, the active layer comprising poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and sol–gel zinc oxide (ZnO) ETL were slot-die coated on flexible PET/ITO substrate as reference based on the R2R process. Aluminum-doped ZnO (AZO) instead of ZnO was also adopted. For further improving the performance of large-area PSC, we used polyethylenimine ethoxylated (PEIE) material to tailor the nanostructure of ZnO and AZO ETLs for reducing the surface traps on ETLs using two approaches: (1) ZnO/PEIE bilayer formed by sequential deposition and (2) ZnO:PEIE hybrid composite as ETLs. The present work would demonstrate the optimum material (fabrication) parameters and how the performance of the R2R large-area slot-die coated PSC can be improved by modifying the ZnO- and AZO-based ETL structures. We also perform the various measurements and structural characterization to understand the relationship among R2R slot-die coating process, charge transport properties, film structure and photovoltaic performance as increasing the device areas from 1×0.3cm2 (power conversion efficiency: 2.69%) to 1×1cm2.