Atomic-layer additive manufacturing for solar cells

Introduction

The ALAMS project will provide the first application of "atomic-layer additive manufacturing" (ALAM), namely for the prototyping of solar cells in large arrays of microdevices.

ALAM Concept

The ALAM concept combines the principles of additive manufacturing (3D printing) with the atomic resolution achieved by the thin coating technique atomic layer deposition (ALD).

Atomic Layer Deposition (ALD)

In ALD, atomic-level control is achieved by judiciously designing the surface reaction chemistry of molecular precursors at near-room temperature for it to become self-limiting. This renders experimental use of ALD very robust to a wide range of parameter variations, since the film growth occurs in a cyclic, layer-by-layer mode.

Application in 3D Printing

This advantage will be exploited towards 3D printing, an area of application that ALD has never been used for until we built the first ALAM prototype in November 2019.

Prototype Details

This prototype centers around a printhead that delivers the ALD precursors to the gas phase in the vicinity of the substrate surface, with a microfluidic element delivering a lateral resolution on the order of micrometers.

Printing Mechanism

The motion of the printhead with respect to the substrate allows the user to print lines and structures of arbitrarily chosen geometries, whereby each pass over a given point of the substrate adds to it exactly the amount of material corresponding to one ALD monolayer. This thickness is typically on the order of an atom, or 0.1 nanometer (depending on the exact ALD reaction used).

Case Study

After developing the ALD chemistry needed for ALAM of the materials required to generate photovoltaic stacks, the ALAMS PoC project will apply it to a case study, namely the rapid prototyping of solar cell microdevices in large arrays.

Broader Implications

The ALAM concept, however, is valid beyond the confines of photovoltaic research. Its commercial potential stems from its position at the convergence of two highly modern, fast-growing markets, namely:

1. Additive manufacturing ('3D printing')
2. Microelectromechanical systems (MEMS)