Interface Recombination of Cu<sub>2</sub>ZnSnS<sub>4</sub> Solar Cells Leveraged by High Carrier Density and Interface Defects

Li, Jianjun; Huang, Jialiang; Huang, Yanchan; Tampo, Hitoshi; Sakurai, Takayasu; Chen, Chao; Sun, Kaiwen; Yan, Chang; Cui, Xin; Mai, Yaohua; Hao, Xiaojing

doi:10.1002/solr.202100418

Cited by 34 publications

(43 citation statements)

References 41 publications

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“…According to our recently established rationally simplified interface Shockley–Real–Hall (SRH) recombination model, [ 32 ] the relatively high density of acceptor‐like interface defects of the monolayer sample may significantly reduce the band‐bending of absorber, the associated build‐in electric field, and the depletion region (as confirmed by the C–V and DLCP measurements). The reduced band‐bending of absorber could be translated to a reduced V OC as interfacial recombination will be dominating in this case.…”

Section: Resultsmentioning

confidence: 99%

“…The reduced band‐bending of absorber could be translated to a reduced V OC as interfacial recombination will be dominating in this case. [ 32 ] While the reduced build‐in electric field may reduce the charge separation capability at the p‐n junction, [ 33 ] thus being responsible for the reduced FF. On the other hand, the carrier collection efficiency and related J SC seem not limited by the acceptor‐like interface defects.…”

Section: Resultsmentioning

confidence: 99%

“…The different nonradiative recombination at the heterojunction interface and the depletion region between the monolayer sample and the bilayer sample may be closely related to their different growth processes and the different final local composition, [9] which will be investigated elsewhere. According to our recently established rationally simplified interface Shockley-Real-Hall (SRH) recombination model, [32] the relatively high density of acceptor-like interface defects of the monolayer sample may significantly reduce the bandbending of absorber, the associated build-in electric field, and the depletion region (as confirmed by the C-V and DLCP measurements). The reduced band-bending of absorber could be translated to a reduced V OC as interfacial recombination will be dominating in this case.…”

Section: Device Analysismentioning

confidence: 90%

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Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

Huang

Cong

et al. 2021

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The persistent double layer structure whereby two layers with different properties form at the front and rear of absorbers is a critical challenge in the field of kesterite thin‐film solar cells, which imposes additional nonradiative recombination in the quasi‐neutral region and potential limitation to the transport of hole carriers. Herein, an effective model for growing monolayer CZTSe thin‐films based on metal precursors with large grains spanning the whole film is developed. Voids and fine grain layer are avoided successfully by suppressing the formation of a Sn‐rich liquid metal phase near Mo back contact during alloying, while grain coarsening is greatly promoted by enhancing mass transfer during grain growth. The desired morphology exhibits several encouraging features, including significantly reduced recombination in the quasi‐neutral region that contributes to the large increase of short‐circuit current, and a quasi‐Ohmic back contact which is a prerequisite for high fill factor. Though this growth mode may introduce more interfacial defects which require further modification, the strategies demonstrated remove a primary obstacle toward higher efficiency kesterite solar cells, and can be applicable to morphology control with other emerging chalcogenide thin films.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Device Analysismentioning

confidence: 90%

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Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

Huang

Cong

et al. 2021

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“…[23] The lower carrier density may reduce the quasi-Femi level splitting in the quasi-neutral region, thus limiting the increase of V OC . [27] On the other hand, the lower acceptorlike defects and shallower acceptor defects could effectively reduce the interface non-radiative recombination by means of reducing the N A , increasing the hole lifetime at interface (τ p ), and increasing the band bending (qV b ) according to the heterojunction interface recombination model established by Li et al [53] In a word, the reduced density and activation energy of acceptor-like defects induced by incorporation of Ag on top of CZTSSe absorber may significantly promote the carrier collection efficiency and may also greatly contribute to the increase of V OC by reducing the non-radiative interface recombination.…”

Section: Device Performancementioning

confidence: 99%

N‐Type Surface Design for p‐Type CZTSSe Thin Film to Attain High Efficiency

Sun

Qiu

et al. 2021

Advanced Materials

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ment of CZTSSe is a large open-circuit voltage deficit (V OC,def ). Many optimization strategies borrowed from CIGSSe solar cells have been used to break through the current high V OC,def issue of CZTSSe materials, including isovalent cation doping [5][6][7][8][9][10][11] and gradient band-gap design. [12] Ag is equivalent to Cu but its ion radius is larger than that of Cu, which will reduce the recombination caused by the high density of Cu/Zn antisite defects, thereby reducing V oc,def . [5,13] Simultaneously, Ag doping can enlarge the band gap (E g ) of the absorber layer, which will be effective for increasing the open voltage (V OC ) of thin film photovoltaic devices. [12,[14][15][16][17] Based on the above advantages of Ag doping, our group prepared Ag-doped (Ag,Cu) 2 ZnSnSe 4 solar cells through pre-alloying followed by a selenization process, and the V OC of the devices was improved. [12] There is, however, a problem with incorporating Ag into kesterite film, i.e., Ag diffuses very quickly and easily distributes uniformly throughout the whole absorber film during the high temperature annealing process. Therefore it is difficult to control the content along the depth of CZTSSe films. [14,18] Theoretical calculations and experimental results both show that Ag 2 ZnSn(S,Se) 4 is an n-type material and can form a p-n junction with CZTSSe, [13,15,19] but it cannot ensure the existence of n-type (Cu,Ag) 2 ZnSn(S,Se) 4 on the surface due to the quick diffusion of Ag. So far, surface type As a low-cost substitute that uses no expensive rare-earth elements for the high-efficiency Cu(In,Ga)(S,Se) 2 solar cell, the Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cell has borrowed optimization strategies used for its predecessor to improve its device performance, including a profiled band gap and surface inversion. Indeed, there have been few reports of constructing CZTSSe absorber layers with surface inversion to improve efficiency. Here, a strategy that designs the CZTSSe absorber to attain surface modification by using n-type Ag 2 ZnSnS 4 is demonstrated. It has been discovered that Ag plays two major roles in the kesterite thin film devices: surface inversion and front gradient distribution. It has not only an excellent carrier transport effect and reduced probability of electron-hole recombination but also results in increased carrier separation by increasing the width of the depletion region, leading to much improved V OC and J SC . Finally, a champion CZTSSe solar cell renders efficiency as high as 12.55%, one of the highest for its type, with the open-circuit voltage deficit reduced to as low as 0.306 V (63.2% Shockley-Queisser limit). The band engineering for surface modification of the absorber and high efficiency achieved here shine a new light on the future of the CZTSSe solar cell.

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“…We anticipate the improved heterojunction interface via this simple and promising strategy would help decrease energy losses for future highperformance kesterite/chalcopyrite-based optoelectronics. In future work, according to the recent results of device simulation, [48] adjusting the carrier density of the absorber layer and passivating the detrimental acceptor-like interface defects are fundamental ways to improve the photovoltage and efficiency of CZTSSe solar cells to a more competitive level. Two Preparation Methods of In 1-x CdxS Buffer Layer: The In-doped CdS buffer layers were deposited on the selenized CZTSSe films via a CBD method.…”

Section: Discussionmentioning

confidence: 99%

Rational Design of Heterojunction Interface for Cu₂ZnSn(S,Se)₄ Solar Cells to Exceed 12% Efficiency

Tian

et al. 2022

Solar RRL

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The photovoltaic performance of the kesterite Cu2ZnSn(S,Se)4 solar cells is still far below its predecessor CuInGaSe2. One major reason is its severe interface nonradiative recombination at the mismatched Cu2ZnSn(S,Se)4/CdS heterojunction interface, leading to a large open‐circuit voltage loss. Herein, a distinctive indium‐incorporation (DI) strategy is developed to deposit an In1−xCdxS buffer layer for optimizing the heterojunction interface. The results reveal that adopting this DI method can effectively inhibit the formation of an undesirable secondary phase, and indium can be more easily doped into the bulk lattice of CdS to form additional beneficial shallow donor InCd defects, which significantly improve the electrical properties of the CdS layer and the quality of the heterojunction interface. Besides, the energy band alignment is adjusted to facilitate the extraction and transfer of interfacial charges, and thus reducing the nonradiative charge recombination at the front Cu2ZnSn(S,Se)4/CdS heterojunction interface. Consequently, the combination of the above enhances the power conversion efficiency from 10.2% to 12.4%, one of the highest for this type of cells, which corresponds to an open‐circuit voltage deficit (Voc,def) reduction to as low as 0.54 V. The strategy provides a rational design for optimizing the heterojunction interface of Cu2ZnSn(S,Se)4 solar cells to reduce voltage loss and achieve high efficiency.

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Interface Recombination of Cu₂ZnSnS₄ Solar Cells Leveraged by High Carrier Density and Interface Defects

Cited by 34 publications

References 41 publications

Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

N‐Type Surface Design for p‐Type CZTSSe Thin Film to Attain High Efficiency

Rational Design of Heterojunction Interface for Cu₂ZnSn(S,Se)₄ Solar Cells to Exceed 12% Efficiency

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Interface Recombination of Cu2ZnSnS4 Solar Cells Leveraged by High Carrier Density and Interface Defects

Cited by 34 publications

References 41 publications

Large‐Grain Spanning Monolayer Cu2ZnSnSe4Thin‐Film Solar Cells Grown from Metal Precursor

Large‐Grain Spanning Monolayer Cu2ZnSnSe4Thin‐Film Solar Cells Grown from Metal Precursor

N‐Type Surface Design for p‐Type CZTSSe Thin Film to Attain High Efficiency

Rational Design of Heterojunction Interface for Cu2ZnSn(S,Se)4 Solar Cells to Exceed 12% Efficiency

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Product

Resources

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Interface Recombination of Cu₂ZnSnS₄ Solar Cells Leveraged by High Carrier Density and Interface Defects

Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

Large‐Grain Spanning Monolayer Cu₂ZnSnSe₄Thin‐Film Solar Cells Grown from Metal Precursor

Rational Design of Heterojunction Interface for Cu₂ZnSn(S,Se)₄ Solar Cells to Exceed 12% Efficiency