Defect interactions and the role of complexes in the CdTe solar cell absorber

Krasikov, Dmitry; Sankin, Igor

doi:10.1039/c6ta09155e

Cited by 75 publications

(67 citation statements)

References 75 publications

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“…Our simulations confirm that the fast mechanism of Cu activation predicted previously is feasible in realistic device processing. We also confirm the effect of Cu compensation by the residual chlorine in CdTe/CdSeTe bulk predicted from the first principles . Two other important effects revealed in this work include accumulation of uncompensated acceptors at absorber boundaries and suppressed doping activation in high‐Se regions of the CdSeTe absorber.…”

Section: Introductionsupporting

confidence: 84%

“…The set of the elementary defect reactions used in this study is complete for the major elements (Cd, Te, Se, Cl, and Cu) and includes all the defect reactions described in work . However, it does not include other impurities often found in significant quantities inside the absorbers, such as oxygen and sodium.…”

Section: Known Limitations and Uncertaintiesmentioning

confidence: 99%

“…7 in ref. [9]). Note that we describe the interactions of the defect with free charge carriers by detailed reactions using Kröger's approach [14] that allows for both the transient and steady-state analysis, rather than the grand canonical approach [15] limited to equilibrium conditions.…”

Section: Effective Formation Energies Of Ionized Defect Speciesmentioning

confidence: 99%

“…A uniform 3e16 cm À3 initial distribution of neutral (Cl i Cl A ) 0 complexes is set in all three absorbers, which is consistent with the amount of Cl remaining in the grain bulk after the chlorination step. [9] The Cu is introduced in the source layer as a neutral (Cu i Cu A ) 0 complex with the total dose of 3e13 cm À2 to emulate its introduction from CuCl 2 solution in a practical fabrication process.…”

Section: Initial Boundary and Simulated Annealing Conditionsmentioning

confidence: 99%

“…[4][5][6][7][8] Most recently, a comprehensive first-principle study was published on the properties and interactions of the point defects and the role of complexes in p-type doping formation in chlorinated CdTe absorbers. [9] However, to fully utilize these results and bridge the gap between thermodynamic estimates and practical time-bound fabrication processes, one has to account for the kinetic limitations and spatial distributions. These include the diffusion and reaction barriers, the distribution of the electric field in semiconductor regions, as well as the surface processes that introduce reactants and remove products.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Simulations of Cu Doping in Chlorinated CdSeTe PV Absorbers

Sankin

Krasikov

2019

Physica Status Solidi (a)

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This paper reports on 1D kinetic modeling of p‐type doping formation in Cu‐doped chlorinated CdSeTe photovoltaic (PV) absorbers with graded Se profiles. Following the recent progress in kinetic simulations of the defect chemistry in stoichiometric CdTe films, this work extends simulation capabilities to a domain of semiconductor alloy films with graded stoichiometries. The defect formation energies and ionization levels, as well as the diffusion and reaction barriers used in the reaction‐diffusion equations are calculated from the first principles. A new formalism is employed to account for the uncertainty of the defect formation energies in semiconductor alloys caused by unknown local surrounding. The developed methodology is used to model a practical fabrication process of p‐type doping formation in graded CdSeTe absorbers and to study the effect of alloy stoichiometry on the doping activation.

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Section: Introductionsupporting

confidence: 84%

Section: Known Limitations and Uncertaintiesmentioning

confidence: 99%

Section: Effective Formation Energies Of Ionized Defect Speciesmentioning

confidence: 99%

Section: Initial Boundary and Simulated Annealing Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinetic Simulations of Cu Doping in Chlorinated CdSeTe PV Absorbers

Sankin

Krasikov

2019

Physica Status Solidi (a)

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Identification of Recombination Losses in CdSe/CdTe Solar Cells from Spectroscopic and Microscopic Time‐Resolved Photoluminescence

2021

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Due to the lowest‐cost and best reliability, CdTe solar cells are the leading thin‐film photovoltaic technology. Increasing open‐circuit voltage by reducing recombination represents the most promising path toward further improvements. Analysis is needed to identify limitations that cause efficiency losses. To achieve this goal for Cu‐doped CdSe/CdTe solar cells, time‐resolved spectroscopy and microscopy are developed and applied. Recombination lifetimes and radiative efficiency identify that defect‐mediated recombination is the dominant voltage loss mechanism. When carrier lifetimes are averaged over many crystalline grains, they increase from 180 to 430 ns when Al2O3 is applied to the back contact. The quasi‐Fermi‐level splitting correspondingly increases from 880–905 to 906–931 mV, indicating a pathway to overcome the long‐standing 900 mV voltage limitation. However, the dominant recombination losses are attributed to the absorber bulk. From microscopic carrier lifetime measurements, it is identified that space charge fields due to charged grain boundaries (GBs) lead to recombination in the CdTe absorber bulk. At high injection, GB space charge fields are screened, but that occurs above 1 Sun excitation conditions. Alloying with selenium in the near‐interface CdSeTe absorber region reduces GB losses and is identified as one of the factors leading to high radiative and power conversion efficiency.

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