Robust Electron Transport Layers via In Situ Cross-Linking of Perylene Diimide and Fullerene for Perovskite Solar Cells

Abstract

While employing charge transport layers (CTLs) in optoelectronic devices including hybrid perovskite solar cells is essential for high performance, using solution-processed organic semiconductor-based CTLs poses challenges for device fabrication. Cross-linking the organic semiconductor is a viable approach, but cross-linked CTLs require additional development for practical application. Here a facile in situ strategy to prepare a cross-linked electron transport layer (ETL) is demonstrated by employing a semiconducting cross-linker composed of perylenediimide-diazide, together with the fullerene (C60) derivative coded as PCBM. Varying the PCBM ratio the cross-linking conditions affords a tunable ETL that exhibits solvent tolerance, suitable electron mobility (>10–4 cm2 V–1 s–1), and hydrophobicity at cross-linking temperatures as low as 120 °C. In both the n–i–p structure and the p–i–n perovskite solar cells employing our ETL, stable power generation and hysteresis-free performance are achieved. Optimized p–i–n devices with our cross-linked ETL gave power conversion efficiency of over 12% (active area of 1.07 cm2). These results suggest that robust n-type semiconducting films obtained with our cross-linking method are promising as ETLs in practical optoelectronic applications.

Band Alignment in Two-Dimensional Halide Perovskite Heterostructures: Type I or Type II?

“…Hybrid organic–inorganic halide perovskites have emerged as some of the most promising materials for optoelectronic applications, ranging from photovoltaics to photodetectors, light-emitting diodes and lasers, etc., owing to their low fabrication costs and superior photophysical properties. − However, three-dimensional (3D) halide perovskites exhibit poor stability toward moisture and ultraviolet light, which significantly hinders their applications. In contrast, 2D and layered quasi-2D halide perovskites have shown superior stability and water resistance relative to their 3D counterparts. − …”

Recent advances of crosslinkable organic semiconductors in achieving solution-processed and stable optoelectronic devices

“…Furthermore, crosslinkers with azide groups can be added to the ETL to achieve a crosslinkable ETL. 164,165 For instance, Yum et al developed a novel conjugated crosslinker perylenediimidediazide with pendant azide unit (PDI-DA, the chemical structure is illustrated in Fig. 11) crosslinked PCBM under mild heating or UV treatment.…”

“…11) crosslinked PCBM under mild heating or UV treatment. 165 The crosslinkable ETL showed remarkable advantages of solvent resistance, adaptable electron This journal is © The Royal Society of Chemistry 2022 mobility, and hydrophobicity, which effectively achieved strong, stable, and crosslinkable ETL lms in optoelectronic applications.…”

Azido‐Functionalized Fullerenes, Perylenediimide, Perylene, and Tetraphenylethylene as Crosslinkers for Applications in Materials Science

“…Like for crosslinkable HTL materials, such azido derivatives can be used in the electron transport layer (ETL) with the aim of protecting the photoactive layer. In the same way, the semiconducting crosslinker perylenediimide‐diazide (PDI‐DA) was synthesized [35] in order to form a robust ETL through in situ crosslinking of PDI to [60]PCBM for improving efficiency of PerSCs [36] …”