Electrical characterization of vacuum-deposited n-CdS/p-CdTe heterojunction devices

Abstract

The effects of post-deposition processes such as CdCl 2 dip and/or annealing in air on the material and device properties of vacuum-evaporated Au-CdTe/CdS-TO heterojunction solar cells have been investigated. The CdCl 2 dip followed by air annealing at 300 • C for 5 min improved the device efficiency significantly, resulting in decreased CdTe resistivity and enhanced grain size. The temperature-dependent current-voltage analysis indicated that above 280 K interface recombination dominates the current transport mechanism for the as-grown samples, while depletion region recombination starts to be dominant after annealing the samples with CdCl 2 . Below 280 K multistep tunnelling is identified to be the dominant transport mechanism. Frequency-dependent capacitance-voltage studies revealed that after annealing with CdCl 2 the density of interface states decreases and the quality of the heterointerface improves. The capacitance of the CdS/CdTe heterojunctions has been analysed using a model based on the existence of a single dominant trap level, identified at 0.40 eV above the valence band with a concentration of 5.1 × 10 15 cm −3 .

Nanocone Tip–Film Solar Cells with Efficient Charge Transport

“…In planar CdTe cells, an increase in the number of grain boundaries (GBs) and other defects in the CdTe layer leads to a decease in V oc and ff . With CdCl 2 treatment, as shown in the inset of Figure 2 g, the EDS image shows that chlorine atoms are indeed accumulated at GBs, consistent with the result in previous report, [ 18 ] supporting the reported mechanisms that Cl-rich GBs are additional minority carrier pathways. [ 19 , 20 ] This new pathway appears especially pronounced for nanocone junctions.…”

Effect of in situ CdCl2 treatment on spray deposited CdTe∕CdS heterostructure

“…After the CdCl 2 treatment, the transport mechanism is dominated by depletion region recombination due to the decrease in the interface state density. 9 The diffusion of S into CdTe film reduces the CdTe band gap slightly and extends the spectral response to longer wavelengths but reduces the built-in voltage. The reduction of CdS thickness increases light generated current due to greater transmission of short wavelength photons and subsequent absorption in CdTe.…”

Investigation of the Electronic -Properties of Al-CdTe-Au Schottky Diode

“…On the other hand, there can be many reasons to get junction ideality factor greater than unity; Henish H. K. [8] attributed this to the presence of an interfacial layer, image force lowering of barrier height, Sarmah and Rahman [3] attributed to the presence of an interfacial layer and tunneling effect. Bayhan and Erecelebi [9] attributed the increase of (η) to the series resistance effects which are associated with the neutral region of the semiconductor (between depletion layer and ohmic contact). Surface defects produce electronic energy levels in band gabs of CdTe semiconductor.…”