On the physics of dispersive electron transport characteristics in SnO2 nanoparticle-based dye sensitized solar cells

• Published in: Nanotechnology 2018-04, Vol.29 (17), p.175401-175401
• Main Authors: Ashok, Aditya, Vijayaraghavan, S N, Unni, Gautam E, Nair, Shantikumar V, Shanmugam, Mariyappan
• Format: Article
• Language: English
• Subjects: dispersive transport; hysteresis; recombination; solar cell; surface states
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aaae45

The present study elucidates dispersive electron transport mediated by surface states in tin oxide (SnO2) nanoparticle-based dye sensitized solar cells (DSSCs). Transmission electron microscopic studies on SnO2 show a distribution of ∼10 nm particles exhibiting (111) crystal planes with inter-planar spacing of 0.28 nm. The dispersive transport, experienced by photo-generated charge carriers in the bulk of SnO2, is observed to be imposed by trapping and de-trapping processes via SnO2 surface states present close to the band edge. The DSSC exhibits 50% difference in performance observed between the forward (4%) and reverse (6%) scans due to the dispersive transport characteristics of the charge carriers in the bulk of the SnO2. The photo-generated charge carriers are captured and released by the SnO2 surface states that are close to the conduction band-edge resulting in a very significant variation; this is confirmed by the hysteresis observed in the forward and reverse scan current-voltage measurements under AM1.5 illumination. The hysteresis behavior assures that the charge carriers are accumulated in the bulk of electron acceptor due to the trapping, and released by de-trapping mediated by surface states observed during the forward and reverse scan measurements.