Defect study of Cu2ZnSn(SxSe1−x)4 thin film absorbers using photoluminescence and modulated surface photovoltage spectroscopy

Lin, Xianzhong; Ennaoui, A.; Levcenko, S.; Dittrich, Thomas; Kavalakkatt, Jaison; Kretzschmar, Steffen; Unold, Thomas; Lux‐Steiner, Martha Ch.

doi:10.1063/1.4905311

Cited by 34 publications

(20 citation statements)

References 29 publications

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“…Both samples show a red shift of the band maximum up to ≈150 K and blue shift at higher temperatures. Similar dependencies were observed previously for CZTSSe solid solutions with quasi donor‐acceptor pair (QDAP) emission and detailed explanations can be found elsewhere . It is notable that the PL peak of the AT treated sample exhibits blue shift (around 10 mV) in the whole range of temperatures with respect to the reference one.…”

Section: Resultssupporting

confidence: 84%

Enhanced Hetero‐Junction Quality and Performance of Kesterite Solar Cells by Aluminum Hydroxide Nanolayers and Efficiency Limitation Revealed by Atomic‐resolution Scanning Transmission Electron Microscopy

et al. 2018

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A strategy for interface engineering of hetero‐junctions in kesterite solar cells by using Al(OH)3 is demonstrated. The hydroxide nanolayers are prepared via a facile and fast wet chemical route, based on an aqueous solution of aluminum chlorides and thioacetamide. Considerable enhancement of open circuit voltage (Voc) (30–60 mV) and fill factor (FF) (10–20%) after this chemical treatment are observed, achieving a champion conversion efficiency of 9.1% and a champion FF of 70% (among the best FF in kesterite solar cells). The functional mechanism is systematically studied by current‐voltage, capacitance‐voltage, temperature dependence of current–voltage and photoluminescence measurements, which reveal that Al(OH)3 nanolayers can effectively reduce the interface recombination and largely improve the shunt resistance. Furthermore, atomic resolution high angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) evidences the epitaxial relationship of Al(OH)3 with kesterite and CdS, indicating the benign and effective interface passivation achieved by this chemical treatment. Finally, based on HAADF‐STEM and electron energy loss spectroscopy mappings, insights into the efficiency limiting and beneficial factors for CZTSSe solar cells, as well as suggestions to further improve both the bulk and related interfaces are presented.

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Section: Resultssupporting

confidence: 84%

Enhanced Hetero‐Junction Quality and Performance of Kesterite Solar Cells by Aluminum Hydroxide Nanolayers and Efficiency Limitation Revealed by Atomic‐resolution Scanning Transmission Electron Microscopy

et al. 2018

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“…These fluctuations usually determine the asymmetric shape of PL bands, where the shape of the low energy side of the PL spectra is determined by the density of states function. In kesterite samples, γ values in the range γ≈25-80 meV were found [2,3,5,29,[31][32][33][34][35]. Typical low-temperature measurements for kesterites show a broad peak with increasing width and assymmetry for higher sulfur concentrations as shown in figure 2(a).…”

Section: Intrinsic Defects In Kesteritesmentioning

confidence: 90%

“…PL and admittance spectroscopy (AS) are the most used experimental methods to study defects in kesterites. PL studies have shown that most of the kesterite materials show properties that are typical for highly doped and compensated semiconductors [2,5,[27][28][29]. In kesterites, the high doping originates from the very high concentration of charged intrinsic defects (>10 20 cm −1 ) that cause widening of the defect levels within the forbidden gap and induce the spatial potential fluctuations and formation of band tails.…”

Section: Intrinsic Defects In Kesteritesmentioning

confidence: 99%

The electrical and optical properties of kesterites

et al. 2019

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Kesterite Cu 2 ZnSn(S x Se 1-x ) 4 (CZTSSe) semiconductor materials have been extensively studied over the past decade, however despite significant efforts, the open circuit voltage remains below 60% of the theoretical maximum. Understanding the optical and electrical properties is critical to explaining and solving the voltage deficit. This review aims to summarize the present knowledge of optical and electrical properties of kesterites and specifically focuses on experimental data of intrinsic defects, charge carrier density and transport, and minority carrier lifetime and related rate-limiting recombination mechanisms. It concludes with suggestions for further investigation of the electrical and optical properties of kesterite materials. of the (001) cationic planes are randomly occupied by Cu and Zn atoms [6,7]. While theoretical calculations by Chen et al [8] find the lowest formation energy for the kesterite crystal structure, cation disorder is present in CZTSSe due to the low energy difference between the stannite-and kesterite-related structures. It has been suggested that the Cu-Zn disorder in Cu 2 ZnSnS 4 (CZTS) follows a second order phase transition with a critical temperature of ∼260°C for CZTS, which was first observed and introduced to describe the modifications in the Raman spectra of CZTS annealed at different temperatures [9]. A similar phenomenon has also been found in Cu 2 ZnSnSe 4 (CZTSe), with a critical temperature of 200°C [10], where the measured increase in band gap is explained by thermally induced ordering of Cu and Zn cations. While the remarkable effect of the orderdisorder transition on the band gap and vibrational spectra is explained by Vineyard's theory [11], the disorder parameter itself is not experimentally determined in the probed samples. A recent direct comparison between resonant x-ray diffraction and photoluminescence (PL) data in CZTSe has confirmed a relationship between the Cu-Zn disorder and the band gap modification [12]. A change in the order parameter from 0 to 0.7 leads to a OPEN ACCESS RECEIVED significant increase in the band gap on the order of ∼0.11 eV and ∼0.20 eV for CZTSe and CZTS, respectively [10,13].The absorption coefficient for CZTS and CZTSe is about ∼2-3 × 10 4 cm −1 at 1.6 eV and at 1.1 eV, respectively, as determined by the normal reflectance and transmittance [2, 13] spectroscopic ellipsometry (SE) [14-16] and external quantum efficiency [17] methods. In the recent review by Choi et al [18] the main theoretical and experimental results on the energy band structure and SE data were discussed and summarized. Recently, Zamulko et al [19] re-examined first principle theory at different levels in order to improve the description of the electronic structure and optical properties of CZTSSe. Nishiwaki et al [20] performed density functional calculation to study absorption band tail of the kesterites. In particular, a theoretical estimate for the tail energy of ∼30 meV for both CZTS and CZTSe was obtained. It was suggested that quite large Urbach energi...

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“…A summary of some of these recombination models can be found in the review of Teixeira et al [7]. The luminescence observed in CZTSSe is energetically far below the band gap and is often attributed to donor-acceptor pair transitions involving electro static potential fluctuations (so called quasi donor-acceptor pair transitions) [8]. The fluctuations lead to band tails [9] thus influencing the PL behavior.…”

Section: Introductionmentioning

confidence: 98%

The influence of the degree of Cu-Zn disorder on the radiative recombination transitions in Cu2ZnSn(S,Se)4 solar cells

Lang

Zimmermann

Krämmer

et al. 2015

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)

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CU2ZnSn(S,Se)4 absorbers show disorder in the Cu-Zn lattice planes, which affects the band gap energy. The degree of disorder can be changed via post-annealing treatments. We report on the influence of this Cu-Zn disorder on the radiative recombination transitions in CU2ZnSn(S,Se)4 solar cells. Temperature-and power-dependent photoluminescence meas urements were performed to evaluate this influence. With increasing excitation power the samples show a large blue-shift of the photoluminescence peak energy while with increasing temperature at constant excitation power they show a red-shift. From an analysis of the shifting behavior as a function of the degree of Cu-Zn disorder we conclude that the degree of disorder does not alter the dominant recombination mechanism significantly.Index Terms -CU2ZnSn(S,Se)4, order-disorder, photo luminescence.

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Defect study of Cu2ZnSn(SxSe1−x)4 thin film absorbers using photoluminescence and modulated surface photovoltage spectroscopy

Cited by 34 publications

References 29 publications

Enhanced Hetero‐Junction Quality and Performance of Kesterite Solar Cells by Aluminum Hydroxide Nanolayers and Efficiency Limitation Revealed by Atomic‐resolution Scanning Transmission Electron Microscopy

Enhanced Hetero‐Junction Quality and Performance of Kesterite Solar Cells by Aluminum Hydroxide Nanolayers and Efficiency Limitation Revealed by Atomic‐resolution Scanning Transmission Electron Microscopy

The electrical and optical properties of kesterites

The influence of the degree of Cu-Zn disorder on the radiative recombination transitions in Cu2ZnSn(S,Se)4 solar cells

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