Voltage Loss Comparison in CdSe/CdTe Solar Cells and Polycrystalline CdSeTe Heterostructures

Kuciauskas, Darius; Li, Siming; Moseley, John; Albin, David S.; Lee, Chungho; Onno, Arthur; Holman, Zachary C.

doi:10.1109/jphotov.2021.3117914

Cited by 8 publications

(6 citation statements)

References 18 publications

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“…1 shows that the band tails have a non-Urbach (nonexponential) spectral shape, and it is important to consider their possible origin. In polycrystalline CdTe, similar nonexponential band tails were recently reported 24 , 27 . The sub-bandgap absorption coefficient of 100–1000 cm −1 , determined in Ref.…”

Section: Resultssupporting

confidence: 83%

“…The defect assignment is not certain, but the Te antisite and Cd vacancy complex has an activation energy of 0.79 ± 0.06 eV (absorption is shown in Fig. 1 ) 27 . In p-type samples S1 and S2, the values for p = N A − N D were found to be 1 × 10 15 cm −3 and 3 × 10 15 cm −3 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…All these features are important for CdTe optoelectronic devices. For example, band tails in polycrystalline CdTe have been observed using cathodoluminescence 23 , photothermal deflection spectroscopy (PDS) 24 , and absolute photoluminescence (PL) 27 . Our data shows that tails are also present for single-crystal CdTe, which indicates that grain boundaries and dopant accumulation at grain boundaries are not required for tail formation.…”

Section: Resultsmentioning

confidence: 99%

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Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Ščajev

Mekys

Subačius

et al. 2022

Sci Rep

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Cadmium telluride (CdTe) semiconductors are used in thin-film photovoltaics, detectors, and other optoelectronic applications. For all technologies, higher efficiency and sensitivity are achieved with reduced charge carrier recombination. In this study, we use state-of-the-art CdTe single crystals and electro-optical measurements to develop a detailed understanding of recombination rate dependence on excitation and temperature in CdTe. We study recombination and carrier dynamics in high-resistivity (undoped) and arsenic (As)-doped CdTe by employing absorption, the Hall effect, time-resolved photoluminescence, and pump-probe in the 80–600 K temperature range. We report extraordinarily long lifetimes (30 µs) at low temperatures in bulk undoped CdTe. Temperature dependencies of carrier density and mobility reveal ionization of the main acceptors and donors as well as dominant scattering by ionized impurities. We also distinguish different recombination defects. In particular, shallow AsTe and deep VCd−AsCd acceptors were responsible for p-type conductivity. AX donors were responsible for electron capture, while nonradiative recombination centers (VCd−AsTe, As2 precipitates), and native defects (VCd−TeCd) were found to be dominant in p-type and n-type CdTe, respectively. Bimolecular and surface recombination rate temperature dependencies were also revealed, with bimolecular coefficient T−3/2 temperature dependence and 170 meV effective surface barrier, leading to an increase in surface recombination velocity at high temperatures and excitations. The results of this study allowed us to conclude that enhanced crucible rotation growth of As-doped CdTe is advantageous to As activation, leading to longer lifetimes and larger mobilities and open-circuit voltages due to lower absorption and trapping.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Ščajev

Mekys

Subačius

et al. 2022

Sci Rep

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“…The improvement of the slow component (τ 3 ), which is commonly related to the bulk recombination, implies a longer survival time for the carriers in the bulk, enabling the carriers coming back to the absorber from the TCO in the later times and contributing to the TRPL decay 41 . PLQY was further used to predict the ideal V OC (iV OC ) and the iV OC difference (ΔiV OC ) for the control and target devices 42 , 43 . The expected ΔiV OC can be expressed as .…”

Section: Resultsmentioning

confidence: 99%

20%-efficient polycrystalline Cd(Se,Te) thin-film solar cells with compositional gradient near the front junction

Bista

Awni

et al. 2022

Nat Commun

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Bandgap gradient is a proven approach for improving the open-circuit voltages (VOCs) in Cu(In,Ga)Se2 and Cu(Zn,Sn)Se2 thin-film solar cells, but has not been realized in Cd(Se,Te) thin-film solar cells, a leading thin-film solar cell technology in the photovoltaic market. Here, we demonstrate the realization of a bandgap gradient in Cd(Se,Te) thin-film solar cells by introducing a Cd(O,S,Se,Te) region with the same crystal structure of the absorber near the front junction. The formation of such a region is enabled by incorporating oxygenated CdS and CdSe layers. We show that the introduction of the bandgap gradient reduces the hole density in the front junction region and introduces a small spike in the band alignment between this and the absorber regions, effectively suppressing the nonradiative recombination therein and leading to improved VOCs in Cd(Se,Te) solar cells using commercial SnO2 buffers. A champion device achieves an efficiency of 20.03% with a VOC of 0.863 V.

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“…Given a negligible effect of recombination on current, it is natural to expect its similarly weak effect on device voltage thus questioning the role of SRH recombination altogether. There is however an alternative hypothesis claiming a significant deficit (loss) of PV voltages and relating it to recombination either directly or defined vaguely in terms of 'material quality' exhibiting itself e. g. in Urbach tails [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. More specifically, the open circuit voltage (V oc ) deficit is defined as…”

Section: Introductionmentioning

confidence: 99%

Voltage deficit in PV with suppressed recombination

Karpov

Shvydka

2023

Applied Physics Letters

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The observed open circuit voltages in best performing solar cells are explained outside of the recombination paradigm, based on such factors as electrostatic screening, Meyer–Neldel effect, and lateral nonuniformities. The underlying concept of suppressed recombination presents a long neglected alternative pathway to efficient photovoltaic. The criteria of suppressed recombination and effective charge carrier extraction are consistent with the data for best performing solar cells.

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Voltage Loss Comparison in CdSe/CdTe Solar Cells and Polycrystalline CdSeTe Heterostructures

Cited by 8 publications

References 18 publications

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

20%-efficient polycrystalline Cd(Se,Te) thin-film solar cells with compositional gradient near the front junction

Voltage deficit in PV with suppressed recombination

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