The advancement of metal halide perovskite solar cells (PSCs) hinges on achieving high performance while ensuring long-term operational stability. In this study, we present a comprehensive investigation—both experimental and theoretical—of two complementary approaches to interfacial engineering in perovskite solar devices, centered on the design and implementation of electroactive organic spacer molecules. 

We explore the possibility to introduce electroactive organic spacers at the perovskite/ETL interface inverted (p–i–n) PSC architectures to mitigate non-radiative recombination while simultaneously enhancing charge extraction.[1] Density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations support experimental observations by revealing how these spacers facilitate interfacial charge transfer and stabilize the interface. We further investigate their role in fullerene-free architectures, identifying electronic design criteria for spacer molecules that enable both passivation and efficient transport.

Also, we examine the incorporation of π-conjugated aryl-acetylene-based spacers into hybrid layered (2D/3D) perovskite structures.[2] Spacers such as (4-ethynylphenyl)methylammonium (BMAA) and buta-1,3-diyne-1,4-diylbis(4,1-phenylene)dimethylammonium (BDAA) not only passivate surfaces and inhibit the transition to non-photoactive phases, but also participate actively in charge transport. Experimental characterization shows that mixed-dimensional perovskite devices incorporating these spacers achieve power conversion efficiencies up to 23% and exhibit superior operational stability. Theoretical analyses highlight favorable energy level alignment and strong orbital delocalization through the π-conjugated backbones for BDAA, enabling effective coupling with charge transport layers. 

Together, these findings provide design principles for multifunctional electroactive interlayers that simultaneously enhance stability, suppress recombination, and facilitate efficient charge transport. 

[1] K.K. Armadorou*, Ghewa AlSabeh*, A. Vezzosi*, M. Najafov, P. Zimmermann, U. Röthlisberger, L. Pfeifer, F. T.  Eickemeyer, J. V. Milić, M. Grätzel et al., Manuscript under review, J. Mater. Chem. C, 2025
[2] AlSabeh, G.*; Slama, V.*; Ren, M.; Almalki, M.; Pfeifer, L.; Kubicki, D. J.; Zimmermann, P.; Hinderhofer, A.; Faini, F.; Moia, D.; Othman, M.; Eickemeyer, F. T.; Carnevali, V.; Lempesis, N.; Vezzosi, A.; Ansari, F.; Schreiber, F.; Maier, J.; Wolff, C. M.; Hessler‐Wyser, A.; Ballif, C.; Grancini, G.; Rothlisberger, U.; Grätzel, M.; Milić, J. V. Aryl‐Acetylene Layered Hybrid Perovskites in Photovoltaics. Angew. Chem. Int. Ed. 2025, e202417432. https://doi.org/10.1002/anie.202417432.