Charge carrier recombination models based on fluence dependent time resolved photoluminescence (TRPL) datasets can provide crucial insights into the optoelectronic properties of semiconducting materials. In the case of halide perovskites, the validity of the assumed recombination model is however often challenged [1], where an ongoing debate exists on the number and type of defect populations to consider, such that a multitude of defect populations need to be assumed to reproduce experimental data even of a canonical perovskite thin film [2]. In systems with enhanced complexity, such as perovskite quantum dot solids presenting pronounced diffusion processes [3], a modelling with common recombination models fails and an alternative approach as well as a validation protocol of the assumed models is required.

Herein, we present a novel TRPL data representation method that allows to (1) extract recombination constants from complex material systems beyond common recombination models and (2) simultaneously evaluate the validity of assumed processes in the different recombination models (such as the presence and type of defects) [4]. To do so, a method that processes time-resolved datasets to absolute carrier density-resolved datasets is developed. By analyzing different derivative representations, monomolecular and bimolecular recombination processes are graphically isolated, where a rigorous comparison of experimental and simulated datasets allows their clear association to different recombination processes as well as to equilibrium and out-of-equilibrium processes. This enables, among others, a clear distinction between shallow and deep trap contributions. The proposed analysis method is applied to different systems and the extracted recombination constants are validated through simultaneously acquired fluence dependent PLQY curves.

The proposed approach provides thus a broadly applicable analysis tool that allows to differentiate between different recombination and charge transfer processes and helps to identify the dominant contributions in a given semiconducting system, with largely varying defect populations and diffusion pathways.

[1] Kiligaridis, A., Frantsuzov, P. A., Yangui, A., Seth, S., Li, J., An, Q., ... & Scheblykin, I. G. (2021). Are Shockley-Read-Hall and ABC models valid for lead halide perovskites?. Nature communications, 12(1), 3329.

[2] Yuan, Y., Yan, G., Dreessen, C., Rudolph, T., Hülsbeck, M., Klingebiel, B., ... & Kirchartz, T. (2024). Shallow defects and variable photoluminescence decay times up to 280 µs in triple-cation perovskites. Nature Materials, 23(3), 391-397.

[3] Tiede, D. O., Romero-Pérez, C., Koch, K. A., Ucer, K. B., Calvo, M. E., Srimath Kandada, A. R., ... & Míguez, H. (2024). Effect of Connectivity on the Carrier Transport and Recombination Dynamics of Perovskite Quantum-Dot Networks. ACS nano, 18(3), 2325-2334.

[4] Tiede, D. O. et al – in preparation