Bayesian parameter estimation for characterising mobile ion vacancies in perovskite solar cells

TL;DR

This paper introduces a Bayesian parameter estimation method to quickly characterize mobile ion vacancies in perovskite solar cells from simple J-V measurements, aiding rapid device optimization and stability analysis.

Contribution

The paper presents a novel Bayesian approach to invert drift-diffusion models for perovskite solar cells, enabling fast and precise extraction of ion vacancy parameters from experimental data.

Findings

Accurately characterized ion vacancy density and diffusion coefficient.

Demonstrated method's effectiveness on both simulated and real devices.

Potential to identify degradation mechanisms in perovskite solar cells.

Abstract

To overcome the challenges associated with poor temporal stability of perovskite solar cells, methods are required that allow for fast iteration of fabrication and characterisation, such that optimal device performance and stability may be actively pursued. Currently, establishing the causes of underperformance is both complex and time-consuming, and optimisation of device fabrication thus inherently slow. Here, we present a means of computational device characterisation of mobile halide ion parameters from room temperature current-voltage (J-V) measurements only, requiring $\sim 2$ hours of computation on basic computing resources. With our approach, the physical parameters of the device may be reverse modelled from experimental J-V measurements. In a drift-diffusion model, the set of coupled drift-diffusion partial differential equations cannot be inverted explicitly, so a method for inverting the drift-diffusion simulation is required. We show how Bayesian Parameter Estimation (BPE) coupled with a drift-diffusion perovskite solar cell model can determine the extent to which device parameters affect performance measured by J-V characteristics. Our method is demonstrated by investigating the extent to which device performance is influenced by mobile halide ions for a specific fabricated device. The ion vacancy density $N_0$ and diffusion coefficient $D_I$ were found to be precisely characterised for both simulated and fabricated devices. This result opens up the possibility of pinpointing origins of degradation by finding which parameters most influence device J-V curves as the cell degrades.