Very small tail state formation in Cu2ZnGeSe4

Nagaya, Keisuke; Fujimoto, Sanji; Tampo, Hitoshi; Kim, Shinho; Nishiwaki, Mitsutoshi; Nishigaki, Youichi; Kato, Masato; Shibata, Hajime; Fujiwara, Hiroyuki

doi:10.1063/1.5031799

Cited by 29 publications

(39 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Among the most relevant pure Ge kesterite results, Schnabel et al reported efficiencies exceeding 5% for a sulfo-selenide CZGSSe (E g ∼1.5 eV) solar cell [124], while for the selenide CZGSe (Eg∼1.4 eV) compound, Sahayaraj et al published a 5.5% efficiency device with a remarkable V OC of 744 mV [125]. Intriguingly, the Ge based kesterite showed less electrical losses from band tailing/electrostatic potential fluctuations compared to Ge free devices [125,126]. However, the main limiting factors were linked to a high series resistance, leading to imperfect current collection and a high interface recombination [127].…”

Section: Germanium (Ge)mentioning

confidence: 99%

Doping and alloying of kesterites

et al. 2019

View full text Add to dashboard Cite

Attempts to improve the efficiency of kesterite solar cells by changing the intrinsic stoichiometry have not helped to boost the device efficiency beyond the current record of 12.6%. In this light, the addition of extrinsic elements to the Cu 2 ZnSn(S,Se) 4 matrix in various quantities has emerged as a popular topic aiming to ameliorate electronic properties of the solar cell absorbers. This article reviews extrinsic doping and alloying concepts for kesterite absorbers with the focus on those that do not alter the parent zinc-blende derived kesterite structure. The latest state-of-the-art of possible extrinsic elements is presented in the order of groups of the periodic table. The highest reported solar cell efficiencies for each extrinsic dopant are tabulated at the end. Several dopants like alkali elements and substitutional alloying with Ag, Cd or Ge have been shown to improve the device performance of kesterite solar cells as compared to the nominally undoped references, although it is often difficult to differentiate between pure electronic effects and other possible influences such as changes in the crystallization path, deviations in matrix composition and presence of alkali dopants coming from the substrates. The review is concluded with a suggestion to intensify efforts for identifying intrinsic defects that negatively affect electronic properties of the kesterite absorbers, and, if identified, to test extrinsic strategies that may compensate these defects. Characterization techniques must be developed and widely used to reliably access semiconductor absorber metrics such as the quasi-Fermi level splitting, defect concentration and their energetic position, and carrier lifetime in order to assist in search for effective doping/alloying strategies.

show abstract

Section: Germanium (Ge)mentioning

confidence: 99%

Doping and alloying of kesterites

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The tail state formation in a-Si:H is caused by the random nature of the amorphous network [34]. Quite large tail absorption in CZTSe and CZTS has been attributed to cation disorder (i.e., Cu/Zn/Sn mixing) [35,36], while the tail state generation is negligible in Cu 2 ZnGeSe 4 (CZGSe) due to the suppression of the cation mixing [36]. been incorporated into the calculation by adopting experimental data, while an unrealistic step function with E U = 0 eV is assumed for the light absorption in the SQ model.…”

Section: Shadow Loss 5% Neglectedmentioning

confidence: 99%

Maximum Efficiencies and Performance-Limiting Factors of Inorganic and Hybrid Perovskite Solar Cells

et al. 2019

Self Cite

View full text Add to dashboard Cite

The Shockley and Queisser limit, a well-known efficiency limit for a solar cell, is based on unrealistic physical assumptions and its maximum limit is seriously overestimated.To understand the power loss mechanisms of record-efficiency cells, a more rigorous approach is necessary. Here, we have established a formalism that can accurately predict absolute performance limits of solar cells in conventional thin film form. In particular, a formulation for a strict evaluation of the saturation current in a nonblackbody solar cell has been developed by taking incident angle, light polarization and texture effects into account. Based on the established method, we have estimated the maximum efficiencies of 13 well-studied solar cell materials [GaAs, InP, CdTe, a-HC(NH 2 ) 2 PbI 3 ] in a 1-µm-thick physical limit. Our calculation shows that over 30% efficiencies can be achieved for absorber layers with sharp absorption edges (GaAs, InP, CdTe, CuInGaSe 2 , Cu 2 ZnGeSe 4 ). Nevertheless, many record-efficiency polycrystalline solar cells, including hybrid perovskites, are limited by open-circuit voltage and fill-factor losses. We show that the maximum conversion efficiencies described here present alternative limits that can predict the power generation of real-world solar cells. *fujiwara@gifu-u.ac.jp sc J kT qV J J −  

show abstract

“…14 Recently, Dhawale et al reported an improvement in the V oc -deficit mainly due to the reduced band tailing obtained by controlling the Ge/(Sn + Se) ratio. 18 Nagaya et al reported the advantages of Ge in CZTS, 19 with a very small tail state formed in CZGSe compared to the large band tailing observed in CZTS and CZTSe. In a previous study, our low-temperature Time-Resolved Photoluminescence (TRPL) Cu 2 ZnGeSe 4 data suggest that a dominant contribution to the observed band tailing in CZT(S,Se) samples comes from the electrostatic potential fluctuations which is totally absent in the Cu 2 ZnGeSe 4 absorber.…”

Section: Introductionmentioning

confidence: 99%