Quantifying Charge Extraction and Recombination Using the Rise and Decay of the Transient Photovoltage of Perovskite Solar Cells

TL;DR

This paper introduces a new analytical method to quantify charge extraction and recombination dynamics in perovskite solar cells by analyzing transient photovoltage rise and decay times, linking these processes to efficiency losses.

Contribution

It presents a novel approach combining rise and decay times of transient photovoltage with a linearized differential equation model to extract recombination and extraction rates.

Findings

Determined carrier recombination and extraction rates as functions of bias voltage.

Linked the ratio of these rates to efficiency losses in perovskite solar cells.

Provided an analytical solution for transient photovoltage dynamics.

Abstract

The extraction of photogenerated charge carriers and the generation of a photovoltage belong to the fundamental functionalities of any solar cell. These processes happen not instantaneously but rather come with finite time constants, e.g., a time constant related to the rise of the externally measured open circuit voltage following a short light pulse. The present paper provides a new method to analyze transient photovoltage measurements at different bias light intensities combining rise and decay times of the photovoltage. The approach uses a linearized version of a system of two coupled differential equations that is solved analytically be determining the eigenvalues of a 2 x 2 matrix. By comparison between the eigenvalues and the measured rise and decay times during a transient photovoltage measurement, we determine the rates of carrier recombination and extraction as a function of bias voltage and establish a simple link between their ratio and the efficiency losses in the perovskite solar cell.