Electron recombination dynamics in CdSe/P3HT hybrid heterojunctions

The combination in hybrid heterojunction of nanocrystals and semiconductor polymers has great potential for light-toenergy conversion devices. For this reason, a great number of different quantum dots/polymer molecular solar cells have been investigated. However, less attention has been paid to the photo-induced charge transfer processes at the interface of these systems. Here we report a time resolved spectroscopic study of the electron injection and recombination transfer steps of CdSe/P3HT bulk heterojunction films. From the data obtained using Time Correlating Single Photon Counting (TCSPC) we have inferred that electron injection from P3HT excited state to CdSe nanocrystal conduction band occurs faster than 250 ps and the electron yield is higher than 85%, independently of the nanocrystal shape. On the other hand, the use of Laser Transient Absorption Spectroscopy allowed us to observe that all the studied interfacial charge transfer process can be fitted to dispersive stretched exponentials kinetics, independently of the QD's concentration and nanocrystal morphology, thereby offering evidence of multiple decay process in CdSe/P3HT bulk heterojunctions.

[1]  Peng,et al.  Charge separation and transport in conjugated-polymer/semiconductor-nanocrystal composites studied by photoluminescence quenching and photoconductivity. , 1996, Physical review. B, Condensed matter.

[2]  Ilan Gur,et al.  Hybrid Organic-Nanocrystal Solar Cells , 2005 .

[3]  J. Durrant,et al.  Transient emission studies of electron injection in dye sensitised solar cells , 2008 .

[4]  V. Bulović,et al.  Inorganic-organic hybrid solar cell: bridging quantum dots to conjugated polymer nanowires. , 2011, Nano letters.

[5]  Jun-Ho Yum,et al.  CdSe Quantum Dot-Sensitized Solar Cells Exceeding Efficiency 1% at Full-Sun Intensity , 2008 .

[6]  Michael Grätzel,et al.  Solar energy conversion by dye-sensitized photovoltaic cells. , 2005, Inorganic chemistry.

[7]  Weimin Zhang,et al.  Charge carrier formation in polythiophene/fullerene blend films studied by transient absorption spectroscopy. , 2008, Journal of the American Chemical Society.

[8]  Christopher B. Murray,et al.  Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies , 2000 .

[9]  Nagarjuna Gavvalapalli,et al.  Role of Molecular Architecture in Organic Photovoltaic Cells , 2010 .

[10]  S. Yoshikawa,et al.  One-Dimensional Nanostructured Semiconducting Materials for Organic Photovoltaics , 2010 .

[11]  Jean-Luc Brédas,et al.  Charge transport in organic semiconductors. , 2007, Chemical Reviews.

[12]  Ullrich Scherf,et al.  Efficiency enhancement for bulk-heterojunction hybrid solar cells based on acid treated CdSe quantum dots and low bandgap polymer PCPDTBT , 2011 .

[13]  Tracey M. Clarke,et al.  Analysis of Charge Photogeneration as a Key Determinant of Photocurrent Density in Polymer: Fullerene Solar Cells , 2010, Advanced materials.

[14]  Lin-Wang Wang,et al.  Colloidal nanocrystal heterostructures with linear and branched topology , 2004, Nature.

[15]  Tracey M. Clarke,et al.  Free Energy Control of Charge Photogeneration in Polythiophene/Fullerene Solar Cells: The Influence of Thermal Annealing on P3HT/PCBM Blends , 2008 .

[16]  Emilio Palomares,et al.  Control of charge recombination dynamics in dye sensitized solar cells by the use of conformally deposited metal oxide blocking layers. , 2003, Journal of the American Chemical Society.

[17]  N. S. Sariciftci,et al.  Conjugated polymer-based organic solar cells. , 2007, Chemical reviews.

[18]  F. Rauscher,et al.  Photo-induced charge recombination kinetics in low bandgap PCPDTBT polymer:CdSe quantum dot bulk heterojunction solar cells , 2011 .

[19]  D. Ginley,et al.  The Effect of Nanoparticle Shape on the Photocarrier Dynamics and Photovoltaic Device Performance of Poly(3‐hexylthiophene):CdSe Nanoparticle Bulk Heterojunction Solar Cells , 2010 .