Ashok Aditya, Vijayaraghavan S N, Unni Gautam E, Nair Shantikumar V, Shanmugam Mariyappan
Amrita Center for Nanosciences and Molecular Medicine, Amrita Vishwa Vidyapeetham, Kerala-682041, India.
Nanotechnology. 2018 Apr 27;29(17):175401. doi: 10.1088/1361-6528/aaae45. Epub 2018 Feb 9.
The present study elucidates dispersive electron transport mediated by surface states in tin oxide (SnO) nanoparticle-based dye sensitized solar cells (DSSCs). Transmission electron microscopic studies on SnO 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 SnO, is observed to be imposed by trapping and de-trapping processes via SnO 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 SnO. The photo-generated charge carriers are captured and released by the SnO 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.
本研究阐明了基于氧化锡（SnO）纳米颗粒的染料敏化太阳能电池（DSSC）中由表面态介导的色散电子传输。对SnO的透射电子显微镜研究表明，存在分布的~10 nm颗粒，呈现出（111）晶面，面间距为0.28 nm。观察到，SnO主体中光生电荷载流子所经历的色散传输是由靠近带边的SnO表面态的俘获和去俘获过程所导致的。由于SnO主体中电荷载流子的色散传输特性，该DSSC在正向（4%）和反向（6%）扫描之间观察到性能有50%的差异。光生电荷载流子被靠近导带边的SnO表面态俘获和释放，导致非常显著的变化；这在AM1.5光照下的正向和反向扫描电流 - 电压测量中观察到的滞后现象得到了证实。滞后行为确保了电荷载流子由于俘获而在电子受体主体中积累，并在正向和反向扫描测量期间由表面态介导的去俘获过程释放。
