Electrophoresis Assisted Printing: A Method To Control the Morphology in Organic Thin Films

Abstract

A major advantage of organic solar cells (OSC) is the processability out of solution allowing for advanced printing methods toward large-scale production. Controlling the blend morphology of solution coated active layers is a key challenge to optimize their power conversion efficiency. We have derived a printing procedure from an industrial coating process that facilitates tuning the nanomorphology of a blend of poly­(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as model system for OSCs. Applying an electric field during printing and the film drying process modifies the vertical film composition of the photoactive layer and optimizes the polymer crystal orientation. The choice of chloroform as solvent allows us to obtain material transport within the wet film, due to an induced electrophoretic mobility. Tailoring the morphology improves the power conversion efficiency of the OSCs by up to 25%. Our findings indicate that electrophoresis assisted printing provides an efficient approach to optimize the active layer for various material and solvent combinations that exhibit an electrophoretic mobility.

Spark Discharge Doping—Achieving Unprecedented Control over Aggregate Fraction and Backbone Ordering in Poly(3‐hexylthiophene) Solutions

“…[ 53,54 ] We already demonstrated this property in a previous work by the positive electrophoretic mobility of P3HT in CF and used it to move P3HT in a wet thin film driven by an electric field. [ 55 ] If P3HT is further positively charged beyond this intrinsic effect, that is, further electrons are transferred from P3HT to CF, charge remains localized on the P3HT for a longer time. The reason is that the CF − anion is unstable, and a Cl − anion splits off upon charging a CF molecule negatively.…”

Effect of Time and Voltage on the Electrophoresis Deposition of Zinc Oxide Thin Films for Photovoltaic Applications

“…V.F et al [19], electrodeposited zinc oxide at 30, 40, and 50 V for application on DSSCs; Proller. S. et al [24], deposited organic thin films by EPD, achieving a power conversion efficiency of 25%. Das.…”

Origin of Hole Transport in Small Molecule Dilute Donor Solar Cells

“…Recently, single-junction organic solar cells (OSCs) reached remarkable power conversion efficiencies (PCEs) of 18%, [1][2][3] facilitated by the usage of novel materials, especially nonfullerene acceptors, [4,5] and increased control of film morphologies. [6][7][8] Understanding the generation of free charge carriers from absorbed photons is fundamental to design novel organic semiconductors and to tailor the electronic properties of interfaces in donor:acceptor blends for efficient solar cells. Despite the rapid increase in efficiencies, we are still lacking a detailed understanding of the motion of photogenerated charge carriers within the multiphase thin films consisting of crystalline and amorphous domains, or even strongly mixed donor: acceptor phases.…”