Self-Assembling for Efficient Perovskite Solar Cells

In recent years, solar cells based on metal halide perov­skites have achieved an exceptional increase in efficiency. These materials promise cost-effec­tive and flexible solar cells, and can be combined with conven­tional PV materials such as silicon to form parti­cularly efficient tandem solar cells. An impor­tant step towards mass pro­duction is the development of efficient electrical contact layers that would allow deposition of perovskite layers on various substrates.

Perovskite monolayer: The molecule organises itself on the electrode surface until a dense, uniform monolayer is formed. (Source: S. Magomedoviene, HZB)

Now the Helmholtz Zentrum Berlin HZB Young Inves­tigator Group headed by physicist Steve Albrecht, in colla­boration with Artiom Mago­medov from Kaunas Univer­sity of Tech­nology (KTU) in Lithuania, has synthesized a novel molecule that self-assembles into a mono­layer (SAM). The team success­fully used this new material as a hole-conducting layer in perov­skite solar cells. The molecule is carbazole-based and bonds to the oxide of the trans­parent electrode via a phos­phonic acid anchoring group. Due to the anchoring fragment, this molecule organises itself on the electrode surface until a dense, uniform monolayer is formed. The ultra-thin layer exhibits no optical losses and, thanks to its self-orga­nising property, could confor­mally cover any surface – including textured silicon in tandem solar-cell archi­tectures.

Extremely low material consump­tion is achieved with this technique, and the chemical structure of the SAMs can be adapted to the desired appli­cation. Thus, SAMs could also serve as a model system for future inves­tigations of the proper­ties of perovskite inter­faces and growth. The work took place at the HySPRINT labora­tory of the HZB where Albrecht’s group is now conducting research on a new gene­ration of self-assembling molecules, which already enable solar cells with effi­ciencies of over 21 %. Since this approach to perov­skite solar cells has never been considered before and can poten­tially play a role in indus­trial processes, the HZB and KTU teams have filed a patent appli­cation on the molecule and its use. (Source: HZB)

Reference: A. Magomedov et al.: Hole Transporting Monolayers: Self‐Assembled Hole Transporting Monolayer for Highly Efficient Perovskite Solar Cells, Adv. Ener. Mat. 8, 1870139 (2018); DOI: 10.1002/aenm.201870139

Link: Young Investigator Group Perowskite Tandem Solar Cells, Helmholtz Zentrum Berlin HZB, Berlin, Germany

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