Processing Additives for Improved Efficiency from Bulk Heterojunction Solar Cells

TLDR

The authors studied 1,8‑di(R)octanes with various functional groups as processing additives for bulk heterojunction solar cells. They identified that additives with selective fullerene solubility and higher boiling point control BHJ morphology, and using 1,8‑diiodooctane increased device efficiency from 3.4 % to 5.1 %.

Abstract

Two criteria for processing additives introduced to control the morphology of bulk heterojunction (BHJ) materials for use in solar cells have been identified: (i) selective (differential) solubility of the fullerene component and (ii) higher boiling point than the host solvent. Using these criteria, we have investigated the class of 1,8-di(R)octanes with various functional groups (R) as processing additives for BHJ solar cells. Control of the BHJ morphology by selective solubility of the fullerene component is demonstrated using these high boiling point processing additives. The best results are obtained with R = Iodine (I). Using 1,8-diiodooctane as the processing additive, the efficiency of the BHJ solar cells was improved from 3.4% (for the reference device) to 5.1%.