Impact of morphology on loss mechanisms in printed solar cells

• Applicant: Professor Dr. Carsten Deibel
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461909888

The dual aims of this project are to a) understand loss mechanisms in all-printed organic solar cells based on non-fullerene acceptors (NFAs), and b) to use this understanding to predict the final performance of printed large area NFA-based devices. We will focus on how the on nanomorphology (nm scale) and microstructure (μm scale) of printed organic layers affect recombination yield and transport losses, and how it ultimately impacts the performance of printed solar photovoltaic devices. Both physical experiments and numerical simulation will be used to underpin this work. A "hyperspectral" approach will be developed, to map the absolute photon emission spectra from charge transfer complexes upon optical excitation, in order to predict the open circuit voltage of printed active layers before the deposition of electrodes. The interpretation will be supported by a microscopic 2D network model, corresponding to the solar cell surface, where each node consists of a complete drift–diffusion simulation. We will also study the impact of the nanomorphology – measured and modelled within the consortium – on the device physics by a combination of experiments and 3D drift–diffusion simulations. For a deeper understanding, we will account for the detailed recombination losses by measuring charge carrier concentration and lifetime in the frequency domain. We will evaluate the experimental data by global fitting using the drift–diffusion model with machine learning to understand the bottlenecks limiting overall device and material performance. This approach will enable gaining a detailed understanding of both the device physics on different length scales, and how these physical processes ultimately affect the device characteristics of large area printed solar cells. In combination with the other projects within the POPULAR consortium, we will be able to unravel the function–property relations of printed NFA-based organic solar cells.

• DFG Programme: Research Units
• Subproject of: FOR 5387: Printed & Stable Organic Photovoltaics from Non-Fullerene Acceptors
• International Connection: United Kingdom
• Major Instrumentation: System for CT photoluminescence mapping
• Instrumentation Group: 0260 Strahlungsmeßplätze (außer 033, 330-339, 405 und 615-619)
• Cooperation Partner: Professor Dr. Roderick MacKenzie