Combinatorial Reactive Sputtering of In₂S₃ as an Alternative Contact Layer for Thin Film Solar Cells

Abstract

High-throughput computational and experimental techniques have been used in the past to accelerate the discovery of new promising solar cell materials. An important part of the development of novel thin film solar cell technologies, that is still considered a bottleneck for both theory and experiment, is the search for alternative interfacial contact (buffer) layers. The research and development of contact materials is difficult due to the inherent complexity that arises from its interactions at the interface with the absorber. A promising alternative to the commonly used CdS buffer layer in thin film solar cells that contain absorbers with lower electron affinity can be found in β-In2S3. However, the synthesis conditions for the sputter deposition of this material are not well-established. Here, In2S3 is investigated as a solar cell contact material utilizing a high-throughput combinatorial screening of the temperature-flux parameter space, followed by a number of spatially resolved characterization techniques. It is demonstrated that, by tuning the sulfur partial pressure, phase pure β-In2S3 could be deposited using a broad range of substrate temperatures between 500 °C and ambient temperature. Combinatorial photovoltaic device libraries with Al/ZnO/In2S3/Cu2ZnSnS4/Mo/SiO2 structure were built at optimal processing conditions to investigate the feasibility of the sputtered In2S3 buffer layers and of an accelerated optimization of the device structure. The performance of the resulting In2S3/Cu2ZnSnS4 photovoltaic devices is on par with CdS/Cu2ZnSnS4 reference solar cells with similar values for short circuit currents and open circuit voltages, despite the overall quite low efficiency of the devices (∼2%). Overall, these results demonstrate how a high-throughput experimental approach can be used to accelerate the development of contact materials and facilitate the optimization of thin film solar cell devices.

Combinatorial In Situ Photoelectron Spectroscopy Investigation of Sb2Se3/ZnS Heterointerfaces

“…Up to 5.6% efficiency has been demonstrated for thin film solar cells based on Sb 2 Se 3 /CdS heterojunctions . Toxicity concerns motivate the investigation of alternative buffer layers for novel absorber materials . Potential candidates for environmentally friendly buffer layers include In 2 S 3 , ZnS, and Zn(O,S) .…”

“…The composition and thickness were mapped using X‐ray fluorescence (Fischer, Fischerscope XDV‐SDD). A more detailed description of the combinatorial deposition and characterization can be found in the literature …”

Fulfilling the promise of the materials genome initiative with high-throughput experimental methodologies

“…Therefore, HTE techniques should be additionally applied to processing parameters, interface engineering, and performance of multilayer stacks/devices. Foundational demonstrations of HTE screening for integrated materials have been made in the fields of photovoltaics 37,134 and solar fuels. 135 To further the evolution of HTE technologies for component-level materials development, it is necessary to develop HTE metrologies that measure interface properties (e.g., electronic, magnetoelectric, and photonic) and grain boundary effects on device performance and reliability.…”

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

“…In 2 S 3 is one of the most studied alternative buffer layers for different kesterite-based TFSCs [167,168,170,171]. Among various crystalline forms, the β-In 2 S 3 phase has a defective spinel structure that leads to a better stability and optoelectronic properties, in addition to a suitable interface formation with several emerging absorber materials [167,172]. CBD-In 2 S 3 was applied as buffer in CZTSSe-based devices giving efficiencies very close to that of the CdS [107] as seen in table 2.…”