Analytical Model for Light Modulating Impedance Spectroscopy (LIMIS) in All-Solid-State p-n Junction Solar Cells at Open-Circuit

TL;DR

This paper develops an analytical model for Light Intensity Modulated Impedance Spectroscopy (LIMIS) in all-solid-state p-n junction solar cells at open-circuit, linking it to surface recombination processes and offering a basis for future detailed simulations.

Contribution

It introduces an analytical approach to LIMIS signals in p-n junction solar cells, connecting impedance responses with surface recombination velocity, advancing beyond traditional numerical methods.

Findings

LIMIS signal correlates with surface recombination velocity.

Analytical solutions for IS, IMPS, and IMVS are derived.

LIMIS differs from standard impedance spectroscopy, providing new insights.

Abstract

Non-circuit theory drift-diffusion numerical simulation of standard potentiostatic impedance spectroscopy (IS) is a well-known strategy for characterization of materials and electronic devices. It implies the time-dependent solutions from the continuity and Poisson's equations under small perturbation of the bias boundary condition at the electrodes. But in the case of photo-sensitive devices a small light perturbation can be also taken modulating the generation rate along the absorber bulk. In that focus, this work approaches a set of analytical solutions for the signals of IS and intensity modulated photocurrent and photovoltage spectroscopies, IMPS and IMVS respectively, from one-sided p-n junction solar cells at open-circuit. Subsequently, a photo-impedance signal named light intensity modulated impedance spectroscopy (LIMIS equals IMVS over IMPS) is analytically simulated and its difference with respect to IS suggests a correlation with the surface charge carrier recombination velocity. This is an illustrative result and starting point for future more realistic numerical simulations.