Thin film solar cells based on metal halide perovskite (ABX3, A= Cs,[CH₃NH₃] (MA),[CH (NH₂)₂] (FA); B= Pb, Sn; X= Cl, Br, I) have gained vigorous attention from both academic and industry during the past few years due to the impressive light-to-electricity conversion efficiency of 25.2% and potentially low-cost manufacturing. The wide bandgap with flexibility to tune over broad energy range renders perovskite solar cells ideal candidates for top cells in tandem applications with well-established narrow bandgap bottom cells, such as crystalline-Si and thin-film Cu(In,Ga)Se₂ (CIGS) to realize highly-efficient and cost-effective tandem devices. This approach presents a viable pathway to improving efficiency of commercial Si or CIGS beyond 30% whilst maintaining low manufacturing cost. Our research activities are focused on developing efficient and stable perovskite solar cells with high near-infrared transmittance for highly efficient perovskite-CIGS all-thin-film tandem photovoltaics.

Main research topics include:

1. NIR-transparent perovskite solar cells using scalable vapor deposition method.
2. Fundamental understanding of the non-radiative recombination centers in the device using a variety of advanced characterization techniques.
3. All-thin-film perovskite/CI(G)S tandem solar cells on both rigid and flexible substrates.
4. Long-term stability of perovskite solar cells under operational conditions.

• Fan Fu, Stefano Pisoni, Quentin Jeangros, Jordi Sastre-Pellicer, Maciej Kawecki, Adriana Paracchino, Thierry Moser, Jeremie Werner, Christian Andres, Leo Duchene, Peter Fiala, Michael Rawlence, Sylvain Nicolay, Christophe Ballif, Ayodhya N. Tiwari, Stephan Buecheler. I₂ vapor-induced degradation of formamidinium lead iodide based perovskite solar cells under heat-light soaking conditions. Energy and Environmental Science 12, 3074-3088 (2019).
• Stefano Pisoni, Fan Fu, Roland Widmer, Romain Carron, Thierry Moser, Oliver Groening, Ayodhya N. Tiwari, Stephan Buecheler. Impact of interlayer application on band bending for improved electron extraction for efficient flexible perovskite mini-module. Nano Energy 49, 300-307 (2018).
• Stefano Pisoni, Fan Fu, Thomas Feurer, Mohammed Makha, Benjamin Bissig, Shiro Nishiwaki, Ayodhya N. Tiwari, Stephan Buecheler. Flexible NIR-transparent perovskite solar cells for all-thin-film tandem photovoltaic devices. Journal of Materials Chemistry A 5, 13639-13647 (2017).
• Fan Fu, Thomas Feurer, Thomas P. Weiss, Stefano Pisoni, Enrico Avancini, Christian Andres, Stephan Buecheler, Ayodhya N. Tiwari. High-efficiency inverted semi-transparent planar perovskite solar cells in substrate configuration. Nature Energy 2, 16190 (2016).
• Fan Fu, Thomas Feurer, Timo Jäger, Enrico Avancini, Benjamin Bissig, Songhak Yoon, Stephan Buecheler, Ayodhya N. Tiwari. Low-temperature-processed efficient semi-transparent planar perovskite solar cells for bifacial and tandem applications. Nature Communications 6, 8932 (2015).