Polymer aggregation correlated transition from Schottky-junction to bulk heterojunction organic solar cells

Authors

Bin Yang, University of Nebraska–Lincoln
Zhengguo Xiao, University of Nebraska–LincolnFollow
Jinsong Huang, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2014

Citation

APPLIED PHYSICS LETTERS 104, 143304 (2014)

Comments

Copyright 2014 AIP Publishing LLC.

Abstract

The fullerene-based organic Schottky-junction solar cells have recently attracted intensive research interest because of their unique electrical performance, such as significant photocurrent generation from excitons created in fullerenes and large open-circuit voltage (V_OC) output induced by high Schottky-barrier height between the anode and the fullerene acceptor. This manuscript reports another remarkably appealing advantage that the fullerene-based Schottky-junction solar cells are more stable than the bulk heterojunction counterparts. The better stability is likely due to mitigative polymer photo-oxidation and/or little morphological change of active film in the aged Schottky-junction devices. The transition from Schottky-junction to bulk heterojunction appears at polymer donor loading ratio of 20–25 wt.% by examining the variation in the V_OC with increased loading ratio of the poly(3-hexylthiophene) donor. Multiple experimental evidences, including the absorbance spectrum measurement, photoluminescence study, active film morphology characterization, and charge mobility measurement, conclusively reveal that the transition from Schottky-junction to bulk heterojunction is correlated to the polymer donor aggregation in the active films.