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Project Highlights

Hansen 3D space

Selection of green solvents of organic solar cells via binary solvent gradient method

LEITAT has demonstrated the use of the Binary Solvent Gradient Method (BSG) for the design of green ink formulations of polymer/fullerene for bulk-heterojunction solar cells by calculation of the Hansen solubility parameters (HSP). A list of suitable green solvents is obtained from a computer simulation using the HSP of both components and the junction. The aim of this work is to use a new approach to calculate the HSP with less experimental effort and formulate polymer/fullerene inks using non-conventional solvents reducing health and environmental hazards during the OPV manufacturing process.


Xylene-AA

Non-halogenated xylene/anisaldehyde solution for efficient polymer solar cells

Within the MatHero Project, non-halogenated solvents are being identified for a green fabrication of organic solar cells. While examples exist to replace the main solvent, commonly (di)chlorobenzene, very few alternatives exist for the solvent additive 1,8-diiodooctane, which is very often used to optimize the nanomorphology of the polymer:fullerene blend. We found the non-halogenated and eco-compatible additive p-anisaldehyde that, together with o-xylene or anisole as main solvents, yields highly efficient solar cells with several high performance polymers:fullerene bulk-heterojunction photo-active layers. The solvent additive p-anisaldehyde improves film formation, enhances polymer order, reduces fullerene agglomeration and shows high volatility, thereby positively affecting layer deposition, improving charge carrier extraction and reducing drying time, the latter being crucial for future large area roll-to-roll device fabrication.

Publication available at: http://dx.doi.org/10.1039/C5EE01917F.


Encapsulation

Planarization layers for a monolithic encapsulation of organic solar modules

To improve OPV lifetime, Arkema and CEA develop a thin film encapsulation process in order to replace the common, and costly, lamination of high gas barrier films. First, CEA and Arkema developed a planarization layer able to level the surface of the device (see figure). The planarization inks developed in the Mathero project are fully compatible with OPV devices (no degradation) and are able to protect temporally the device from the atmosphere (pre-encapsulation role during a transfer of materials in a given process or before lamination on the final application for example). In addition, the smooth surface makes suitable the subsequent deposition of the high gas barrier structure to warranty long lifetime.

Mini Modules

Mini solar module based on photo-active polymer and non-halogenated solvent deposition developed in MatHero

Developed at Fraunhofer IAP and Advent Technologies, benzodithiophene-quinoxaline polymers were incorporated in organic solar cells and mini solar modules at KIT. Combining the best polymer and a non-halogenated solvent formulation of xylene and anisaldehyde, mini modules with an active area power conversion efficiency of up to 5.8% were fabricated.