Abstract
The electron transport layer (ETL) is very crucial for enhancing the device performance of polymer solar cells (PSCs). Meanwhile, thickness-insensitive and environment-friendly water/alcohol soluble processing are two essential requirements for large-scale roll-to-roll commercial application. Based on this, we designed and synthesized two new n-type ETLs with tetraethylene pentamine or butyl sulfonate sodium substituted tetraethylene pentamine as the branched side chains and high electron affinities perylene diimide (PDI) as the central core, named as PDIPN and PDIPNSO3Na. Encouragingly, both PDIPN and PDIPNSO3Na can effectively reduce the interfacial barrier and improve the interfacial contact. In addition, both of them can exhibit strong n-type self-doping effects, especially the PDIPN with higher density of negative charge. Consequently, compared to bare ITO, the PCE of the devices with ITO/PDIPN and ITO/PDIPNSO3Na ETLs has increased to 3–4 times. Our research results indicate that n-type self-doping PDI-based ETL PDIPN and PDIPNSO3Na could be promising candidates for ETL in environment-friendly water/alcohol soluble processing large-scale PSCs.
Highlights
Polymer solar cells (PSCs) have attracted increasing attention due to their lightweight, flexibility, and easy large-area solution processability [1–11]
ΔΦ means the difference in the work function of ITO, ITO/PDIPN and ITO/PDIPNSO3Na according to the ultraviolet photoelectron spectroscopy (UPS), −HOMO = hν − (Ecutoff − Eonset), hν = 21.22 Ecutoff levels (eV)
3Na3 cause the corresponding polymer solar cells (PSCs) to have have acceptable power conversion efficiency (PCE) on a relatively broad range of interlayer thickness, especially in the device based on PDIPN electron transport layer (ETL)
Summary
Polymer solar cells (PSCs) have attracted increasing attention due to their lightweight, flexibility, and easy large-area solution processability [1–11]. Metal oxide semiconductor (TiOx , ZnO, MoOx ), electrolytes and fullerenes derivates etc have between active layer and cathode electrode should be an effective strategy to increase the been used as ETLs to modulate interfacial contact and reduce interfacial barriers [28–34]. Strong interfacial control capability is extremely urgent It would be electron better if affinities, the ETL ishigh is a with famous n-type material, which has many strong points, such as good thickness-insensitive and can be efficient different interlayer reaction thickness.[35–38]. Conductivities and facile modification by in simple substitution theishigh a famous n-type material, which has many strong points, such as good electron affinities, high conductivity of the PDI originated from self-organized p-stacks in solid film can endow the PDT-based conductivities and facile modification by simple substitution reaction.
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