Simulations of photoconductivity and lifetime for steady state and nonsteady state measurements

Abstract

Contact less measurements of the minority carrier “lifetime” and the photoconductivity are widely used to characterize the material quality and to investigate defects in a sample. In order to interpret these measurements correctly and to guarantee comparability between different methods, numerical simulation tools were developed. These simulations allow to account even for very complex defect models, thus, e.g., enabling the simulation of trapping effects. Contrary to the Shockley–Read–Hall model or the widely used simulation tool PC1D nearly no assumptions are made. Furthermore, nonsteady state solutions can be obtained. The simulation approach is explained in detail, along with simulations of the trapping effect on the measured lifetime for different injections, trap parameters, and measuring methods, demonstrating the capabilities of the here presented simulation tool. Temperature and injection dependent lifetime measurements were performed and it is shown how important sample parameters can be extracted using the simulation tool. Additionally an approach is presented to simulate lifetimes for thick samples, where a nonuniform carrier profile has to be taken into account. This enables a comparison of nonsteady state to steady-state lifetime measurement techniques even for thick samples such as ingots.

Methylamine Vapor Exposure for Improved Morphology and Stability of Cesium-Methylammonium Lead Halide Perovskite Thin-Films

“…Minority carrier recombination lifetime values were measured for perovskite thin films by Freiberg Instrument MDP-spotusing a 405 nm laser(180 mW) [4,5]. Perovskite thin films were characterized using Rigaku Smart lab X-ray Diffractometer Cu-K-alpha radiation.…”

Non-steady state transport of charge carriers. An approach based on invariant embedding method

“…Then, G λ (L) is used to calculate the change of carrier density due to the electron photogeneration in each interval τ, and its units will be (particles=cm 3 ). Thereby, the units of factor g λ will be particles=cm 4 .…”

“…Theoretical understanding of non-steady-state transport properties of optically active semiconductors has received relatively less attention despite the wide experimental activity in the field. Nowadays, most of these experiments are described by empirical or semiempirical models, as the multiple trapping model 1,2 or by simulations 3 and numerical solutions (i.e., the donor photoionization model 4 ). However, a few theoretical efforts using first principles were reported; the most prominent one is due to DeVore, 5 where surface effects and volume recombination of photocarriers have been considered for a particular set of boundary conditions.…”

Photoconductivity

“…The parameters of the traps (trap density, energy level, capture cross-section, trapping time) could well be determined from a fit of kinetic data to the model reported by Hornbeck and Haynes (1955). More recently trapping effects were described also for complex defect models by applying numerically a system of generalized rate equations (Schüler et al 2010).…”