Upper limit to the photovoltaic efficiency of imperfect crystals from first principles

Kim, Sung-Hyun; Marquez, J.A.; Unold, Thomas; Walsh, Aron

doi:10.1039/d0ee00291g

Cited by 137 publications

(193 citation statements)

References 72 publications

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“…Notably, the large capture coefficients for the rapid (green) processes are comparable to the most deleterious extrinsic defects in silicon 64 , 65 and the kesterite photovoltaic family. 62 , 66 This classifies V Cd as a “killer center” 67 and demonstrates the potential impediment of this native defect species to the photovoltaic efficiency of untreated CdTe.…”

Section: Trap-mediated Recombinationmentioning

confidence: 92%

Rapid Recombination by Cadmium Vacancies in CdTe

2021

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CdTe is currently the largest thin-film photovoltaic technology. Non-radiative electron–hole recombination reduces the solar conversion efficiency from an ideal value of 32% to a current champion performance of 22%. The cadmium vacancy (V Cd ) is a prominent acceptor species in p -type CdTe; however, debate continues regarding its structural and electronic behavior. Using ab initio defect techniques, we calculate a negative-U double-acceptor level for V Cd , while reproducing the V Cd 1– hole–polaron, reconciling theoretical predictions with experimental observations. We find the cadmium vacancy facilitates rapid charge-carrier recombination, reducing maximum power-conversion efficiency by over 5% for untreated CdTe—a consequence of tellurium dimerization, metastable structural arrangements, and anharmonic potential energy surfaces for carrier capture.

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Section: Trap-mediated Recombinationmentioning

confidence: 92%

Rapid Recombination by Cadmium Vacancies in CdTe

2021

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“…Deep intrinsic defects like Sn Zn antisites and related [Cu Zn +Sn Zn ] clusters act as deep recombination centers, leading to the short carrier lifetime. [ 7,9,10 ] Additionally, the large population of defect clusters like [2Cu Zn +Sn Zn ] introduces considerable potential (i.e., band or electrostatic) fluctuation. [ 11 ] Consequently, the performance of CZTSSe solar cells are currently stagnated by the large open‐circuit voltage ( V OC ) deficit.…”

Section: Figurementioning

confidence: 99%

Defect Control for 12.5% Efficiency Cu₂ZnSnSe₄ Kesterite Thin‐Film Solar Cells by Engineering of Local Chemical Environment

et al. 2020

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over 30% detailed balance limiting efficiency, as well as to its earth-abundant and environment-benign constituents. [1-3] The increase in power conversion efficiency to a record of 12.6% in the last decade has demonstrated the huge potential of these materials. [4,5] However, as one of the most complicated compound semiconductors, kesterite has much more intricate defect chemistry than its counterparts, Cu(In,Ga)Se 2 (CIGS) and CdTe, [6-8] making the control of intrinsic defects a major challenge. Deep intrinsic defects like Sn Zn antisites and related [Cu Zn +Sn Zn ] clusters act as deep recombination centers, leading to the short carrier lifetime. [7,9,10] Additionally, the large population of defect clusters like [2Cu Zn +Sn Zn ] introduces considerable potential (i.e., band or electrostatic) fluctuation. [11] Consequently, the performance of CZTSSe solar cells are currently stagnated by the large open-circuit voltage (V OC) deficit. [12,13] To address the detrimental intrinsic defects and defect clusters in CZTSSe absorber, multiple strategies have been employed. As suggested by the first-principle calculations, the formation energy of intrinsic defects and Kesterite-based Cu 2 ZnSn(S,Se) 4 semiconductors are emerging as promising materials for low-cost, environment-benign, and high-efficiency thin-film photo voltaics. However, the current state-of-the-art Cu 2 ZnSn(S,Se) 4 devices suffer from cation-disordering defects and defect clusters, which generally result in severe potential fluctuation, low minority carrier lifetime, and ultimately unsatisfactory performance. Herein, critical growth conditions are reported for obtaining high-quality Cu 2 ZnSnSe 4 absorber layers with the formation of detrimental intrinsic defects largely suppressed. By controlling the oxidation states of cations and modifying the local chemical composition, the local chemical environment is essentially modified during the synthesis of kesterite phase, thereby effectively suppressing detrimental intrinsic defects and activating desirable shallow acceptor Cu vacancies. Consequently, a confirmed 12.5% efficiency is demonstrated with a high V OC of 491 mV, which is the new record efficiency of pure-selenide Cu 2 ZnSnSe 4 cells with lowest V OC deficit in the kesterite family by E g /q-Voc. These encouraging results demonstrate an essential route to overcome the long-standing challenge of defect control in kesterite semiconductors, which may also be generally applicable to other multinary compound semiconductors.

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“…[ 14 ] The extremely short minority carrier lifetime and serious band‐tailing states limit the maximum open‐circuit voltage of CZTSe to only 0.53 V (0.84 V for CZTS), which is much lower than the bandgap of 1.0 eV (1.5 eV for CZTS), and therefore result in a lower power conversion upper‐limit (20.3% for CZTSe and 20.9% for CZTS). [ 20 ]…”

Section: Introductionmentioning

confidence: 99%

Defect Engineering in Earth‐Abundant Cu₂ZnSn(S,Se)₄ Photovoltaic Materials via Ga³⁺‐Doping for over 12% Efficient Solar Cells

Wang

Tian

et al. 2021

Adv Funct Materials

100

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The efficiency of earth‐abundant Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is considerably lower than the Shockley–Queisser limit. One of the main reasons for this is the presence of deleterious cation disordering caused by SnZn antisite and 2CuZn+SnZn defect clusters, resulting in a short minority carrier lifetime and significant band tailing, leading to a large open‐circuit voltage deficit, and hence, low efficiency. In this study, Ga‐doping is used to increase the CZTSSe solar cell efficiency to as high as 12.3%, one of the highest for this type of cells. First‐principles calculations show that the preference of Ga3+ occupying Zn and Sn sites has a benign effect on suppressing the formation of the SnZn deep donor defects by upwardly shifting the Fermi level, which is further confirmed by deep‐level transient spectroscopy characterization. Besides, the Ga dopants can also form defect‐dopant clusters, such as GaZn+CuZn and GaZn+GaSn, which also have positive effects on suppressing the band‐tailing states. The defect engineering via Ga3+‐doping may suppress the band‐tailing defect with a decreased Urbach energy, elevate the minority carrier lifetime, and in the end, enhance the VOC from 473 to 515 mV. These results provide a new route to further increase CZTSSe‐based solar cell efficiency by defect engineering.

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Upper limit to the photovoltaic efficiency of imperfect crystals from first principles

Abstract: An approach is proposed to predict the impact of point defects on solar cell performance.

Cited by 137 publications

References 72 publications

Rapid Recombination by Cadmium Vacancies in CdTe

Rapid Recombination by Cadmium Vacancies in CdTe

Defect Control for 12.5% Efficiency Cu₂ZnSnSe₄ Kesterite Thin‐Film Solar Cells by Engineering of Local Chemical Environment

Defect Engineering in Earth‐Abundant Cu₂ZnSn(S,Se)₄ Photovoltaic Materials via Ga³⁺‐Doping for over 12% Efficient Solar Cells

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Upper limit to the photovoltaic efficiency of imperfect crystals from first principles

Abstract: An approach is proposed to predict the impact of point defects on solar cell performance.

Cited by 137 publications

References 72 publications

Rapid Recombination by Cadmium Vacancies in CdTe

Rapid Recombination by Cadmium Vacancies in CdTe

Defect Control for 12.5% Efficiency Cu2ZnSnSe4 Kesterite Thin‐Film Solar Cells by Engineering of Local Chemical Environment

Defect Engineering in Earth‐Abundant Cu2ZnSn(S,Se)4 Photovoltaic Materials via Ga3+‐Doping for over 12% Efficient Solar Cells

Contact Info

Product

Resources

About

Defect Control for 12.5% Efficiency Cu₂ZnSnSe₄ Kesterite Thin‐Film Solar Cells by Engineering of Local Chemical Environment

Defect Engineering in Earth‐Abundant Cu₂ZnSn(S,Se)₄ Photovoltaic Materials via Ga³⁺‐Doping for over 12% Efficient Solar Cells