Thermal Evaporation of Perovskite Absorbers for Silicon Perovskite Tandem Solar Cells

Thermal Evaporation of Perovskite Absorbers for Silicon Perovskite Tandem Solar Cells

Internship Description

Perovskite/silicon tandem solar cells are very promising technology to achieve >30% power conversion efficiency target. Despite this technology features promising efficiency potential, several challenges need to be overcome prior to possible industrial application. A particular challenge relates to the fact that to maximize the light coupling into the bottom cells, the tandems require so-called random-pyramid textured bottom cells (with a feature size of several micron, see Fig. 1a). Whereas flat substrates have enormous reflection losses (Fig. 1c), textured substrates enable improved light coupling into the silicon wafers. Textured silicon solar cells are the industrial state-of-the-art, and there is likely little incentive to develop processes on expensive mirror-polished wafers. However, due to the characteristics of textured surfaces, which present irregularities and low-wetting properties, conventional solution techniques cannot be used to deposit the perovskite or the extraction layers. From this, it can be readily understood that the top cell fabrication needs to rely on scalable and conformal deposition methods, with a high degree of uniformity and reproducibility.  For these reasons, we aim in this project to alter our current state-of-the-art solution-based PSC processing procedures as much as possible towards scalable vacuum-based techniques.

 

In this projects, the candidate will perform an evaporation of perovskites precursors and the conversion of the layers will be performed either by co-evaporation or vacuum/solution hybrid based methods. At the end of the internship period, students will learn how to fabricate and optimize perovskite solar cells. The candidate will have a chance to experience the fabrication of fully textured silicon/perovskite tandem solar cells.

Why thermal evaporated perovskites?

Scalability: vacuum based deposition techniques are a well-established technique in several industrial processes.

Reproducibility: thermal evaporation process of perovskite absorbers is not affected by the multitude of uncontrollable parameters typical for solution-processed perovskites.

Uniformity: unlikely solution deposition, evaporation enables uniform deposition, independently from the substrate type.

Low thermal budget: thermal evaporation is a low-temperature process and the substrate can be eventually further cooled to room temperature.

Environmentally benign: evaporation does not involve toxic solvents.

Process flexibility: different perovskite composition can be obtained by evaporation, according to the desired application.

Deliverables/Expectations

Thickness control of the evaporated lead iodide

Optimization of co-evaporated of lead iodide and cesium bromide

Process sophistication for triple cation system perovskites

>23% tandem solar cell efficiency using thermal evaporated perovskites​

Faculty Name

Stefaan De Wolf

Field of Study

Solar Cells