The combination of oxide and heavier chalcogenide layers
in thin film photovoltaics suffers limitations associated with oxygen
incorporation and sulfur deficiency in the chalcogenide layer or with
a chemical incompatibility which results in dewetting issues and defect
states at the interface. Here, we establish atomic layer deposition
(ALD) as a tool to overcome these limitations. ALD allows one to obtain
highly pure Sb2S3 light absorber layers, and
we exploit this technique to generate an additional interfacial layer
consisting of 1.5 nm ZnS. This ultrathin layer simultaneously resolves
dewetting and passivates defect states at the interface. We demonstrate
via transient absorption spectroscopy that interfacial electron recombination
is one order of magnitude slower at the ZnS-engineered interface than
hole recombination at the Sb2S3/P3HT interface.
The comparison of solar cells with and without oxide incorporation
in Sb2S3, with and without the ultrathin ZnS
interlayer, and with systematically varied Sb2S3 thickness provides a complete picture of the physical processes
at work in the devices.
The doping effect of silver on the structure and properties of diamond-like carbon (DLC) films was investigated. The samples were prepared by a process combining acetylene plasma source ion implantation (high-voltage pulses of −10 kV) with reactive magnetron sputtering of an Ag disc. A mixture of two gases, argon, and acetylene was introduced into the discharge chamber as working gas for plasma formation. A negative high-voltage pulse was applied to the substrate holder, thus, accelerating ions towards the substrate. The chemical composition of the deposited films was modified by the respective gas flows and determined using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The silver concentration within the DLC films influenced the structure and the tribological properties. The surface roughness, as observed by scanning electron microscopy, increased with silver concentration. The film structure was characterized by Raman spectroscopy and X-ray diffractometry (XRD). The DLC films were mainly amorphous, containing crystalline silver, with the amount of silver depending on the process conditions. The tribological properties of the films were improved by the silver doping. The lowest friction coefficient of around 0.06 was derived at a low silver content.
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