Effect of Cryogenic Dry Etching on Minority Charge Carrier Lifetime in Silicon

Abstract

Micro‐ and nanostructured silicon surface application is a promising way of photovoltaic development. An enhancement of optical absorption in solar cells can be achieved, for example, using vertically aligned silicon nanostructures with high aspect ratios. Cryogenic plasma etching is a suitable method for such structures' formation; however, there is still lack of data describing an effect of cryogenic inductively coupled plasma (ICP) etching on defect formation in silicon (Si). The defects may act as recombination centers, leading to solar cell characteristics degradation. Herein, the cryogenic dry etching effects on defect formation in float‐zone (FZ) n‐type silicon substrates and on the photovoltaic properties of solar cells made of plasma‐etched silicon substrate are presented. The decrease in low‐injection minority carrier lifetime in silicon from 0.85 to 0.55 ms is observed by photoluminescence decay after the ICP dry etching at −140 °C. This leads to an open‐circuit voltage drop for the (p)a‐Si:H/(n)c‐Si/(n)a‐Si:H heterojunction structure from 680 to 630 mV. A detailed study of the defect properties by deep‐level transient spectroscopy (DLTS), numerical simulation, and its behavior after wet etching and thermal annealing is presented.

Impact of Interface Recombination on Quantum Efficiency of a‐Si:H/c‐Si Solar Cells Based on Si Wires

“…Lifetime may be recovered by removing the damaged layer. [25] A special cleaning procedure was developed to prepare the samples before a-Si:H/c-Si heterojunction formation. The removal of residues of polystyrene spheres was carried out by boiling the samples sequentially in CCl 4 , and then in isopropyl alcohol.…”

“…First, a 1D model was applied to verify the effect of interfaces states on photoelectric properties of planar a-Si:H/c-Si heterojunction solar cells using AFORS-HET software. The I-V curves and external quantum efficiency (EQE) spectra calculated using the model described in the study by Kudryashov et al, [25] which takes into account the effect of interface states, are shown in Figure 1. The density of interface states (D it ) has a significant influence on open-circuit voltage (V OC ) and fill factor, but at the same time D it does not almost affect the EQE spectra and short-circuit current.…”

О Динамических Характеристиках Неровновесных Носителей Заряда В Кремниевых Пластинах

“…Стандартные образцы с известным временем жизни и размерами, рекомендованными в международном стандарте [21], могут быть оптимальными при использования их для калибровки и поверки как контактных, так и бесконтактных средств измерения этого параметра. Но при этом необходимо четко регламентировать процедуру расчета эффективного времени жизни, пересчета его в объемное, или условия измерения, при которых эти параметры совпадают [22][23][24][25]. The article is devoted to the presentation and discussion of the primary results of an experimental study of the possibility of using the modern "transient photoconductance method" and "non-contact quasi steady state photoconductivity method" for a more accurate, accelerated and non-destructive determination of the lifetime of charge carriers in silicon wafers, intended as a base material for the manufacture of high-speed p-n-microelectronic devices and highperformance solar cells.…”

Advances in Silicon‐Nanoelectronics, Nanostructures and High‐Efficiency Si‐Photovoltaics

“…Two more papers also deal with Si nanocrystals, one with the enhancement of the photoluminescence by a metal membrane, the other one with the general crystallization behavior . Four contributions focus on photovoltaic applications: An improved wet‐chemical processing of Si for heterojunction solar cells, a deeper understanding of contact resistivity measurements via the TLM‐method, and the fabrication of nanostructures for enhanced light absorption by cryogenic dry etching and by using self‐assembled nanosphere‐lithography masks . Raman and infrared spectroscopy of Si nanowires with high free carrier densities are studied in ref.…”