Development of Perovskite Solar Cells by Correlating Advanced Optoelectronic Characterization with Fabrication Processing Parameters (DIRECT-PERO)

• Applicant: Sandheep Ravishankar, Ph.D.
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 539945054

Perovskite solar cells are a promising photovoltaic technology for large-scale renewable energy generation in the future. However, the performance of modern perovskite solar cells is hampered by significant defect-mediated recombination losses at the perovskite/transport layer interfaces and poor charge extraction through the relatively low-mobility charge transport layers. These loss mechanisms at the perovskite/transport layer interfaces are poorly understood due to - (1) The inability to accurately isolate the response of a given perovskite/transport layer interface from overlapping signals due to other processes occurring in the entire device or layer stack, and (2) The absence of information regarding the evolution of characteristic perovskite/transport layer interface parameters (e.g. recombination lifetimes and band offsets) versus fabrication processing parameters. These problems prevent the reliable determination of suitable interface design and passivation strategies. Therefore, the objectives of this project are: 1) Accurate characterization and parametrization of voltage-dependent recombination and charge extraction losses at each perovskite/transport layer interface in state-of-the-art, single-junction perovskite solar cells. 2) Determination of the evolution of the fundamental parameters of these loss mechanisms versus key fabrication processing parameters, followed by implementation of ideal processing parameter sets to fabricate high-efficiency perovskite solar cells. These objectives will be achieved using the following strategy: a) Isolation of the response from each perovskite/transport layer interface - Devices of the form metal/insulator/perovskite/transport layer (MISS) and metal/insulator/perovskite/insulator (MISI) will be fabricated, to clearly identify the optoelectronic response of loss mechanisms occurring at a specific perovskite/transport layer interface and in the bulk perovskite layer. b) Accurate calculation of fundamental device parameters across the entire current-voltage curve - Parameters such as recombination lifetimes and charge extraction velocities will be determined at each bias point of the current-voltage curve to provide a holistic analysis of the loss mechanisms. These parameters will be measured and verified by combining multiple optoelectronic methods, surface physics methods and drift-diffusion simulations. c) Correlation of device parameters with fabrication processing parameters - Semi-automated fabrication of MISS and MISI devices as a function of 7 key spincoating processing parameters will be carried out. Subsequent characterization will allow determination of ideal processing parameter sets that minimize losses at the perovskite/transport layer interfaces. d) Implementation of ideal processing parameter sets - Use of the determined ideal processing parameter sets to fabricate high-efficiency, single-junction perovskite solar cells with different transport layer combinations.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Automated spincoating setup
• Instrumentation Group: 0930 Spezialgeräte der Halbleiterprozeßtechnik