Tail State-Assisted Charge Injection and Recombination at the Electron-Collecting Interface of P3HT:PCBM Bulk-Heterojunction Polymer Solar Cells

TitleTail State-Assisted Charge Injection and Recombination at the Electron-Collecting Interface of P3HT:PCBM Bulk-Heterojunction Polymer Solar Cells
Publication TypeJournal Article
Year of Publication2012
AuthorsWang, He, Manas Shah, Venkat Ganesan, M.L. Chabinyc, and Yueh-Lin Loo
JournalADVANCED ENERGY MATERIALS
Volume2
Pagination1447-1455
Date PublishedDEC
ISSN1614-6832
Keywordsinterfacial segregation, lamination, polymer solar cell, tail state-assisted charge injection and recombination
AbstractThe systematic insertion of thin films of P3HT and PCBM at the electron- and hole-collecting interfaces, respectively, in bulk-heterojunction polymer solar cells results in different extents of reduction in device characteristics, with the insertion of P3HT at the electron-collecting interface being less disruptive to the output currents compared to the insertion of PCBM at the hole-collecting interface. This asymmetry is attributed to differences in the tail state-assisted charge injection and recombination at the active layer-electrode interfaces. P3HT exhibits a higher density of tail states compared to PCBM; holes in these tail states can thus easily recombine with electrons at the electron-collection interface during device operation. This process is subsequently compensated by the injection of holes from the cathode into these tail states, which collectively enables net current flow through the polymer solar cell. The study presented herein thus provides a plausible explanation for why preferential segregation of P3HT to the cathode interface is inconsequential to device characteristics in P3HT:PCBM bulk-heterojunction solar cells.
DOI10.1002/aenm.201200361