Master thesis: Laser ablation based interdigitated back-contacted silicon heterojunction solar cells

Jülich Research Centre (FZJ)

Jülich, Germany

Work group:

IEK-5 – Photovoltaik

Area of research:

Diploma & Master Thesis

Starting date:


Contract time limit:


Job description:

Interdigitated back-contacted Silicon Heterojunction (IBC-SHJ) currently hold the efficiency record for mono-crystalline silicon based solar cells 1. Photolithography and shadow mask approaches are currently the standard methods to pattern the amorphous silicon films on the back-side of the device [2, 3]. However, for the commercialization of this device architecture, a mask-less approaches would be the ideal solution.

We have developed a laser-ablation based approach combined with wet-chemical etching, to tackle this issue and have successfully demonstrated a proof-of-concept device efficiency of 17.5%. Our results show that the laser ablation does not damage the passivation quality of the samples 4, rather the wet-etching process leads to unwanted over-etching of the amorphous films thus reducing the overall device performance.

The first goal of this project is to further optimize the laser ablation step, by either i) changing the beam shape from Gaussian to top-hat or ii) by using a tightly focused lens to obtain smaller (21% photo-conversion efficiency.


  • The ideal candidate will major in engineering, physics, material sciences or any related field at a university and have experience and interest in doing practical experiments.

  • He/She must have some basic knowledge about the fundamentals of photovoltaics.

  • Knowledge of laser processing and wet-chemical processes are also advantageous.

  • He/She should be willing to work in the cleanroom with basic chemicals such as solvents, acids and bases.

  • Have good communication skills in English. Working knowledge of German language is also advantageous.

  • Be proactive, social and willing to work with in tandem with different people in the institute.

1 Yoshikawa, K. et al. Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%. Nat. Energy 2, 17032 (2017).2 Paviet-Salomon, B. et al. Interdigitated back contact silicon heterojunction solar cells featuring an interband tunnel junction enabling simplified processing. Sol. Energy (2018) doi:10.1016/j.solener.2018.01.066.3 Nakamura, J. et al. Development of heterojunction back contact Si solar cells. IEEE J. Photovoltaics 4, 1491–1495 (2014).4 Singh, A. et al. Damage-free ablation process for back-contacted silicon heterojunction solar cells. J. Laser Micro Nanoeng. 13, 314–323 (2018).

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Quote Reference: 2020M-033