Bandgap engineering of Cu(In_1-xGa_x)Se_2 absorber layers fabricated using CuInSe_2 and CuGaSe_2 targets for one-step sputtering process

Combinatorial Analysis Methodologies for Accelerated Research: The Case of Chalcogenide Thin‐Film Photovoltaic Technologies

“…Over the years of implementation of the combinatorial approach for the research of thin films, a variety of different techniques have been employed to provide the most complete analysis of graded samples. In the case of thin-film chalcogenides PV technologies, these have been mainly limited to some conventional techniques that provide information about the main physicochemical properties of these materials, including X-ray fluorescence (XRF), [73,75,84,94] energy-dispersive X-ray spectroscopy (EDS), [66,74,86,97] X-ray diffraction (XRD), [73,78,81,94] optical spectroscopy, [78,84,97,98] and photoluminescence (PL) spectroscopy (see Figure 3). [72,81,86,99] In the last years strong ) Schematic illustration of gradient preparation by applying masks: a continuous movement of the shutter mask leads to a linear thickness variation; a stepwise movement of the shutter mask results in a step gradient.…”

“…attention has also been given to Raman spectroscopy, [73,74,86,95] which has shown high potential for the detection and control of secondary phase formation, crystalline quality, structural/compositional polymorphs, etc. [100] Evaluation of these techniques results in several requirements that should be taken into account for combinatorial analysis.…”

“…A first strategy involves the use of coevaporation processes with different elemental targets, [80,117,118] and in these cases the gradients were naturally obtained due to the geometrical configuration of the targets. Another strategy involves the use of sputtering systems, and this includes the use of CuInSe 2 and CuGaSe 2 targets, [73] as well as more complex processes based in a more advanced Intermolecular Tempus'" P-30 High Productivity Combinatorial (HPC) sputtering tool that allows the simultaneous use of four different targets for co-and/or sequential sputtering of Cu, In, and Ga with systematically controlled lateral gradients in composition and thickness within one substrate. [72] Independent of the used deposition techniques, in all the works, the gradient library was obtained, leading to tens or hundreds of different unit cells.…”

“…Over the years of implementation of the combinatorial approach for the research of thin films, a variety of different techniques have been employed to provide the most complete analysis of graded samples. In the case of thin‐film chalcogenides PV technologies, these have been mainly limited to some conventional techniques that provide information about the main physicochemical properties of these materials, including X‐ray fluorescence (XRF), [ 73,75,84,94 ] energy‐dispersive X‐ray spectroscopy (EDS), [ 66,74,86,97 ] X‐ray diffraction (XRD), [ 73,78,81,94 ] optical spectroscopy, [ 78,84,97,98 ] and photoluminescence (PL) spectroscopy (see Figure ). [ 72,81,86,99 ] In the last years strong attention has also been given to Raman spectroscopy, [ 73,74,86,95 ] which has shown high potential for the detection and control of secondary phase formation, crystalline quality, structural/compositional polymorphs, etc.…”

“…However, despite these advantages, the higher degree of control of the compositional gradient that can be achieved with PVD techniques makes them the preferred strategy for synthesizing thin-film combinatorial samples. [64] Focusing on chalcogenidebased solar cells, synthesized by combinatorial methods, there exist several works reporting the employment of sputtering, [69][70][71][72][73][74][75][76][77][78][79] a lower amount of articles report the use of thermal evaporation [80][81][82][83] and CBD, [66,84,85] and there are also reports describing the use of spray coating, [68,86] PLD, [87] and CVD. [88] The experimental setups required for adapting both PVD and CM techniques for the deposition of combinatorial samples are discussed in a review by McGinn.…”