Limitation factors for the performance of kesterite Cu<sub>2</sub>ZnSnS<sub>4</sub>thin film solar cells studied by defect characterization

Yin, Ling; Cheng, Guanming; Feng, Yang; Li, Zhaohui; Yang, Chunlei; Xiao, Xudong

doi:10.1039/c5ra00069f

Cited by 132 publications

(79 citation statements)

References 37 publications

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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: 89%

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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Section: Intrinsic Defects In Kesteritesmentioning

confidence: 89%

The electrical and optical properties of kesterites

et al. 2019

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“…The detrimental effect of the acceptor defect Cu Zn is further amplifi ed because it can bind with donor defects such as Zn Cu and Sn Zn , forming high concentration of Cu Zn +Zn Cu , Cu Zn +Sn Zn , and 2Cu Zn +Sn Zn defect complexes, which can cause band gap and electrostatic potential fl uctuations [36][37][38][39][40][41][42][43] and/or the trapping and recombination of the carriers, thus further limiting the V oc . [ 30,37,[44][45][46][47] To suppress the Cu Zn related defects, Cupoor/Zn-rich growth conditions are required to fabricate high-effi ciency Cu 2 ZnSnS 4 -based solar cells.…”

Section: Solar Cellsmentioning

confidence: 99%

Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu‐ and Ag‐Based Kesterite Compounds

Yuan

Chen

Xiang

et al. 2015

Adv Funct Materials

321

367

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“…[21] As a consequence, severe electrostatic potential fluctuation and associated band tailing are introduced, as evidenced by the pronounced PL red-shifting (Figure 2). [24,35] In addition, the high concentration of acceptor-like Cu Zn defects will pin the interface Fermi level to a low energy level, [2] thus reducing the band bending in the absorber and weakening the electric field of the heterojunction interfaces. As a result, both V OC and fill factor dramatically deteriorate.…”

mentioning

confidence: 99%

Cation Substitution in Earth‐Abundant Kesterite Photovoltaic Materials

et al. 2018

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As a promising candidate for low‐cost and environmentally friendly thin‐film photovoltaics, the emerging kesterite‐based Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have experienced rapid advances over the past decade. However, the record efficiency of CZTSSe solar cells (12.6%) is still significantly lower than those of its predecessors Cu(In,Ga)Se2 (CIGS) and CdTe thin‐film solar cells. This record has remained for several years. The main obstacle for this stagnation is unanimously attributed to the large open‐circuit voltage (V OC) deficit. In addition to cation disordering and the associated band tailing, unpassivated interface defects and undesirable energy band alignment are two other culprits that account for the large V OC deficit in kesterite solar cells. To capture the great potential of kesterite solar cells as prospective earth‐abundant photovoltaic technology, current research focuses on cation substitution for CZTSSe‐based materials. The aim here is to examine recent efforts to overcome the V OC limit of kesterite solar cells by cation substitution and to further illuminate several emerging prospective strategies, including: i) suppressing the cation disordering by distant isoelectronic cation substitution, ii) optimizing the junction band alignment and constructing a graded bandgap in absorber, and iii) engineering the interface defects and enhancing the junction band bending.

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Limitation factors for the performance of kesterite Cu₂ZnSnS₄thin film solar cells studied by defect characterization

Abstract: PL, AS and DLCP have been performed to study the limitation factors for the performance of CZTS solar cells.

Cited by 132 publications

References 37 publications

The electrical and optical properties of kesterites

The electrical and optical properties of kesterites

Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu‐ and Ag‐Based Kesterite Compounds

Cation Substitution in Earth‐Abundant Kesterite Photovoltaic Materials

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Limitation factors for the performance of kesterite Cu2ZnSnS4thin film solar cells studied by defect characterization

Abstract: PL, AS and DLCP have been performed to study the limitation factors for the performance of CZTS solar cells.

Cited by 132 publications

References 37 publications

The electrical and optical properties of kesterites

The electrical and optical properties of kesterites

Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu‐ and Ag‐Based Kesterite Compounds

Cation Substitution in Earth‐Abundant Kesterite Photovoltaic Materials

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Limitation factors for the performance of kesterite Cu₂ZnSnS₄thin film solar cells studied by defect characterization