Simplified evaluation method for light-biased effective lifetime measurements

Abstract

In this letter, we present a simplified evaluation method for light-biased photoconductance decay measurements. The measured effective lifetime is shown to be a differential quantity τeff,d, which may differ significantly from the actual effective lifetime τeff. However, the actual effective lifetime can be approximated by integrating τeff,d directly over the incident power density of the bias light. The quality of the approximation depends mainly on the surface recombination velocity and the wavelength of the used bias light. However, the inaccuracy remains well below 10% for most practical cases.

Models for numerical device simulations of crystalline silicon solar cells—a review

“…In the early days of Si solar cell modeling, the injection condition during lifetime measurements was not always considered important but affected the results. When taking lifetime measurements as input parameters, one may need to consider that they may be differential values of injection-dependent lifetimes [133][134][135][136].…”

“…9 Measured effective surface recombination velocity S eff in dependence of injection density in p-type Si wafers (some polished or textured, most of them shiny etched) passivated with SiO 2 , some using a forming gas anneal (FGA) or an Al anneal (alneal). Absolute (not differential [133][134][135][136]) values from ISFH recombination C n and C p were already determined in the 70ies [132], e.g. by Dziewior and Schmid [153].…”

Effect of SiO<inf>2</inf> thicknesses in thermal-SiO<inf>2</inf>/PECVD-SiN stacks on surface passivation of n-type Cz silicon substrates

“…Both methods show excellent agreement in lifetime measurements. We quantify the upper level of the effective SRV Seff,max by assuming infinite bulk lifetime and calculate Seff,max from [6]:…”

Optical Measurement Techniques of Recombination Lifetime Based on the Free Carriers Absorption Effect

“…The steady-state methods, where the generation rate and the excess carriers density are controlled simultaneously, present the advantage to measure directly the actual lifetime. In fact, in the steady-state conditions, since the generation rate and the recombination rate are equal and proportional to the power density of the bias light, on the approximation that the excess carriers concentration is approximately constant throughout the sample, the result is [75] …”

“…When the injection level is high, that is, when the generated excess carriers concentration Δ is higher than the majority carriers concentration, really the observed transient decay is not a single-exponential and should require, for data extraction, a more complicated treatment. Nevertheless Aberle et al [73][74][75][76] acutely noted that the situation can be treated in small signal regime. They suggested that it can be actuated adding a constant bias of suitable intensity to the pulse pump to generate a constant background carriers concentration, , a lot higher than the excess carriers concentration induced by the pump pulse, ( ).…”