Minority carrier lifetime of silicon solar cells from quasi-steady-state photoluminescence

A heterodyne lock‐in imaging scheme is introduced to overcome NIR camera speed limitations and poor signal‐to‐noise ratios, thereby generating high‐frequency carrierographic imaging up to 10 kHz. A theoretical model was established to investigate the heterodyne signal generation mechanism as well as to extract the major carrier transport parameters by best‐fitting the entire modulation frequency dependence. Good agreement was found between the theoretically predicted and experimentally measured heterodyne amplitude dependence on excitation intensity. A contrast inversion feature in the high‐frequency heterodyne amplitude images was observed. High‐frequency information presents a method for resolving local near‐surface carrier transport parameters from the lumped effective lifetime, thereby providing ac‐diffusion‐length‐controlled depth‐selective/resolved imaging. Heterodyne lock‐in carrierography (LIC) amplitude images of a crystalline silicon wafer at different frequencies.

Section: Introductionmentioning

confidence: 99%

Camera‐based high frequency heterodyne lock‐in carrierographic (frequency‐domain photoluminescence) imaging of crystalline silicon wafers

Sun

Melnikov

Mandelis

2015

“…In addition to the general advantages of dynamic luminescence methods, QSSPL currently features a sensitivity limit in terms of effective lifetime of 1 µs (at 1 Ω cm) 9, it can be used for a lifetime calibration of luminescence images of devices with laterally inhomogeneous electronic quality 10, and it is applicable to metalized devices 11. A recent publication brings up limitations of transient carrier‐lifetime calibration methods – particularly at very high surface recombination velocities 12.…”

Section: Introductionmentioning

confidence: 99%

“…As a dynamic but explicitly nontransient method, QSSPL is unaffected by the addressed limitations – provided the quasi‐steady‐state condition as defined above is rigorously satisfied. Details concerning our current experimental QSSPL setup can be found in literature 9–11.…”

Section: Introductionmentioning

confidence: 99%

Self‐sufficient minority carrier lifetime in silicon from quasi‐steady‐state photoluminescence

Giesecke

Schubert

Warta

2012

Self Cite

Quasi-steady-state photoluminescence is a versatile technique to determine carrier lifetime in silicon. A recent approach extracts carrier lifetime without a priori information about dopant concentration [Appl. Phys. Lett. 97, 092109 (2010)]. It utilizes the phase shift between a time-modulated optical irradiation and the radiative recombination of a sample, while requiring a minimum of two measurements. The present paper is aimed at a generalization thereof that requires only one measurement. It brings about a substantial experimental simplification, significantly improved accuracy and precision, and it opens up paths to access material properties other than lifetime

“…Spectrally resolved light beam induced current (SR‐LBIC) measurements have been performed do determine the local EQE , using different lasers simultaneously with wavelengths of 405, 523, 658, 780, 940, and 1064 nm and a spot size of 50 μm. In addition, the illumination‐dependent charge carrier lifetime characteristics have been measured for the solar cells using the quasi‐steady state photoluminescence (suns‐PL) method on the in‐house developed modulum platform . In this way, the local effective minority charge carrier lifetime τ eff was obtained.…”

Section: Methodsmentioning

confidence: 99%

Back‐Contacted Back‐Junction Si Solar Cells with Locally Overcompensated Diffusion Regions – Comparison of Buried Emitter and Floating Base Design

Reichel

Fell

Hermle

et al. 2019

Back-contacted back-junction n-type Si solar cells with locally overcompensated diffusion regions are investigated in two different designs. In the "buried emitter" design, boron-doped (B-doped) emitter diffusions are partially diffused and locally overcompensated by phosphor-doped (P-doped) back surface field (BSF) diffusions, leading to n-type regions that are overlapping the p-type regions. In the "floating base" design, the B-diffusions are diffused on the entire rear side, so that the P-diffusions are separated from the base by the emitter. Hence, p-type regions exist between the n-type regions, creating opposing p-n junctions and a base that is floating. For the latter design with an efficiency of 17.1%, the open-circuit voltage V oc , the short-circuit current density J sc , and the fill factor FF are significantly reduced by about 25 mV, 5 mA cm À2 , and 4%, respectively, compared to the buried emitter design where 678 mV, 41.5 mA cm À2 , and 76.1%, respectively, and an efficiency of 21.4% can be achieved. Two-dimensional numerical device simulations reveal that, besides junction and/or shunt leakage currents, recombination at the surface of the emitter and electron transport in the Band P-diffusions due to the opposing p-n junctions are detrimental for the performance of the "floating base" solar cell.