Fabrication conditions for efficient organic photovoltaic cells from aqueous dispersions of nanoparticles

Abstract

For environmentally friendly and cost-effective manufacturing of organic photovoltaic (OPV) cells, it is highly desirable to replace haloarenes with water as the active layer fabrication solvent. Replacing an organic solvent with water requires retooling the device fabrication steps. The optimization studies were conducted using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM) as active layer materials. These materials were dispersed in water as blend and separate nanoparticles using the miniemulsion method. Topologies of the active layers were investigated using atomic force microscopy and electron microscopy techniques. We have identified two essential steps to fabricate efficient OPVs from aqueous dispersions: (1) treatment of the hole-transport layer with UV-O 3 to make the surface hydrophilic and (2) the use of an electron-transporting buffer layer for efficient charge extraction. We have also identified relative humidity and substrate temperature as key fabrication parameters for obtaining uniform active layer films. The OPV devices were fabricated using PEDOT:PSS as the hole-transport layer and PCBM as electron-transport layer with Ca/Al as the counter electrode.Efficiencies of 2.15% with a fill factor over 66% were obtained; the efficiency and the fill-factor is the highest among all aqueous processing of P3HT-PCBM nanoparticle solar cells.

Aqueous Nanoparticle Polymer Solar Cells: Effects of Surfactant Concentration and Processing on Device Performance

“…35,37,39 Our results confirm this for PDPP5T:[60]PCBM NP devices (Table 7). Addition of ethanol improves the J SC and PCE.…”

Analysis of Charge Transport and Device Performance in Organic Photovoltaic Devices with Active Layers of Self-Assembled Nanospheres

“…I L = 1.0 is used for the simulation of transient photocurrents in TOF experiments, and I L = 2.08 is used for the simulation of steadystate J−V characteristics under an incident light intensity of 100 mW/cm 2 . 24 For simulations of both types of experiment (TOF and steady light exposure), we have found that the models provide better reproduction of the experimental data if an effective free charge carrier generation rate G 0 is considered explicitly in eqs 1 and 3 instead of using only a bounded electron−hole pair generation rate in eq 5, which is typically done for charge transport modeling in bulk-heterojunction and bilayer photovoltaic devices. 33,34,36 In fact, multiple exciton dissociation pathways are possible.…”

“…21,24 These active layers consist of P3HT:PCBM blend or separate self-assembled spherical nanoparticles. In blend NP assemblies, individual nanoparticles contain both electron donor and electron acceptor materials (i.e., both P3HT and PCBM), while in separate NP assemblies, individual nanoparticles contain either the donor or the acceptor material only (i.e., only P3HT or only PCBM).…”

Water‐Processable Amphiphilic Low Band Gap Block Copolymer:Fullerene Blend Nanoparticles as Alternative Sustainable Approach for Organic Solar Cells

“…[8] In the case of regular device architectures, active layers are commonly deposited on a poly ( [47] Consequently, finding methods to improve the wettability of the PEDOT:PSS surface becomes one of the major issues to be solved to fabricate efficient NP-OPV devices. [14,48] According to Benor et al, UV-O 3 exposure of the PEDOT:PSS surface produces a controlled oxidation of the material. Using surfactants (surface compatibilizing agents) is one potential solution to overcome the wetting issue but, as discussed above, addition of electrically insulating surfactants is highly detrimental for the charge transport in the device active layers.…”

“…[8] Most papers on NP-based organic photovoltaics (NP-OPVs) rely on the miniemulsion method developed by Landfester et al, [9] in which a surfactant is adopted to generate core-shell NPs. [14] These can be further increased to 2.5% for PATs blended with indene bisadduct fullerene derivatives, ICBA. [14] These can be further increased to 2.5% for PATs blended with indene bisadduct fullerene derivatives, ICBA.…”