Hybrid Solar Cells from a Blend of Poly(3‐hexylthiophene) and Ligand‐Capped TiO₂ Nanorods

Abstract

Hybrid bulk heterojunction solar cells based on nanocrystalline TiO2 (nc‐TiO2) nanorods capped with trioctylphosphine oxide (TOPO) and regioregular poly(3‐hexylthiophene) (P3HT) are processed from solution and characterized in order to relate the device function (optical absorption, charge separation, and transport and photovoltaic properties) to active‐layer properties and device parameters. Annealing the blend films is found to greatly improve the polymer–metal oxide interaction at the nc‐TiO2/P3HT interface, resulting in a six‐fold increase of the charge separation yield and improved photovoltaic device performance under simulated solar illumination. In addition, the influence of the organic ligand at the nc‐TiO2 particle surface is found to be crucial for charge separation. Ligand‐exchange procedures applied on the TOPO‐capped nc‐TiO2 nanorods with an amphiphilic ruthenium‐based dye are found to further improve the charge‐separation yield at the polymer–nanocrystal interface. However, the poor photocurrents generated in the hybrid blend devices, before and after ligand exchange, suggest that transport within or between nanoparticles limits performance. By comparison with other donor–acceptor bulk heterojunction systems, we conclude that charge transport in the nc‐TiO2:P3HT blend films is limited by the presence of an intrinsic trap distribution mainly associated with the nc‐TiO2 particles.

Enhancement of Hole Mobility of Poly(3‐hexylthiophene) Induced by Titania Nanorods in Composite Films

“…[ 1 ] Organic-inorganic nanocomposites are one type of advanced material for organic devices because of the expected synergy between the organic and inorganic components, which lead potentially to new physical properties of the composites and various applications in devices, including solar cells, [2][3][4][5][6] phototransistors, [7][8][9] memories, [ 10 ] and sensors. [ 11 ] The composites of a conjugated polymer such as poly(3-hexylthiophene) (P3HT) and inorganic nanoparticles, such as ZnO, TiO 2 , or CdSe, have been used in organic solar cells, and gratifying power conversion effi ciencies (PCEs) up to 3.8% have been obtained.…”

Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

“…24,25 But we find that such composite films have special advantages for the applications in OPTs since the TiO 2 nanoparticles can store charge ͑electrons͒ under light illumination. Recently, we have reported a new type of OPT based on a composite film of P3HT and TiO 2 nanoparticles.…”

A Hybrid Inorganic–Organic Semiconductor Light‐Emitting Diode Using ZrO2 as an Electron‐Injection Layer

“…For example, thermal annealing is commonly used to enhance the penetration of polymers into TiO 2 pores for solar-cell applications. [12,13] Moreover, n-type TiO 2 is known to quench F8BT excitons, and is commonly used as an electron acceptor in both dye-sensitized and hybrid inorganic-polymer solar cells due to its high electron affinity. [14][15][16][17] In contrast, ZrO 2 is not known to quench excitons in such devices, having an electron affinity that is %0.8 eV lower in energy.…”