PP 2196: Understanding and Suppressing Interfacial Charge Recombination for High Performance Perovskite Solar Cells (SURPRISE)

Halide perovskite semiconductors continue to surprise the community by their many extraordinary physical properties. A key for solar cell applications is their highly fluorescent nature likely due to low defect densities despite their simple processability from solution. In combination with long charge carrier diffusion lengths, perovskite solar cells have the potential to reach the power conversion efficiencies of monocrystalline silicon or even of GaAs cells. However, present perovskite devices usually reach significantly lower open-circuit voltages than allowed by the perovskite absorber, which implies that major non-radiative recombination losses occur elsewhere in the multilayer solar cell stack. In particular, for typical pin-type perovskite cells it has been shown that the recombination loss at hybrid perovskite/transport layer (TL) interfaces is usually 1-2 orders of magnitudes larger than the defect recombination in the absorber layer. Consequently, a comprehensive understanding of this key phenomenon is urgently required to further advance the field. In this project, we aim at unravelling the most important mechanisms that govern interfacial recombination in order to devise systematic means to suppress this recombination loss. Fundamental questions that will be addressed include the role of energy level alignment between the perovskite and the TLs, or whether interfacial recombination proceeds primarily through traps at the perovskite surface, across the interface or within the TL. To identify the dominant recombination pathway at the interface we will use a range of complimentary techniques with high time resolution (ps-to-us) such as transient photoluminescence, transient absorption and THz spectroscopy. In combination with numerical simulations, we aim at establishing a comprehensive kinetic model to describe charge transfer and recombination at the interface and to address the working mechanism of wide-gap interlayers. With respect to the role of the interface energetics, an important step will be the determination of all relevant energy levels throughout the multilayer stack using photoelectron spectroscopy in dark and under realistic solar cell conditions. Knowledge of the actual device energetics will allow a deep understanding of solar cell operation through detailed drift-diffusion simulations and also provide essential design rules for efficient TLs. Furthermore, we aim to demonstrate improved pin-type perovskite solar cells (>23% efficiency) by minimizing the impact of interfacial recombination via perovskite (and TL) doping and creation of a back-surface field that repels minority carriers from the interface. Overall, our concerted fundamental approach is expected to greatly improve our understanding of interfacial recombination and will contribute to further approaching the thermodynamic efficiency limit in perovskite solar cells.

Principal investigators
Koch, Norbert Prof. Dr. techn. (Details) (Structure, Dynamics and electronic Properties of Molecular Systems)

DFG - Schwerpunktprogramme

Duration of project
Start date: 11/2019
End date: 10/2022

Research Areas
Experimental Condensed Matter Physics, Physical Chemistry of Solids and Surfaces, Material Characterisation

Research Areas
Experimentelle Physik, kondensierte Materie

Last updated on 2023-25-04 at 06:30