CZTSSe Thin Film Solar Cells Research Articles

Enhancing the photovoltaic efficiency of CZTSSe thin-film solar cells via Ag-doping induced defect modulation

Defect modulation is one of the key factors in determining the performance of solar cells, and the presence of defects tends to adversely affect carrier recombination and transport, thus having a direct impact on both cell stability and efficiency. Ag doping can modulate the defects, but in-depth studies on the mechanism of the effect are needed. Therefore, an in-depth study of the effect of Ag incorporation on the defect modulation mechanism of Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is of great practical significance for understanding the mechanism of action of Ag doping and further optimising the cell performance. In this study, (AgxCu1-x)2ZnSn(S,Se)4 (0 ≤ x ≤ 1) (ACZTSSe) solar cells were successfully prepared by N, N-dimethylformamide (DMF) solution, which have the characteristics of reducing defects and enhancing photovoltaic performance. After the introduction of Ag, the absorber formed a crystal structure with few holes and penetrating top and bottom. And the electrical performance of the solar cell is significantly improved, J0 is reduced from 4.6 × 10−5 A/cm2 to 2.7 × 10−6 A/cm2, and its contribution to the photovoltaic conversion efficiency (PCE) improvement reaches 142%. This indicates that the introduction of Ag helps to optimize the quality of the absorber, thereby reducing the concentration of interfacial and bulk defects. It also reduces carrier recombination and improves carrier lifetime from 0.86 ms to 1.75 ms. Ultimately increasing our cell efficiency from 7.55% to 10.64% when the Ag content reached 5%. These results clearly show that we have successfully achieved the modulation of defects in CZTSSe solar cells by Ag doping.

Innovative surface passivation of CZTSSe thin films: Ammonium sulfide treatment with plasma etching

For CZTS(e) solar cells, the passivation of interfacial defects is crucial for effectively reducing carrier recombination at the interface. This study examined the combined impact of plasma etching and surface sulfuration on the passivation of interface defects in CZTSSe thin films. The results indicated that plasma etching could improve the surface quality of the thin films and passivate surface defects. The (NH4)2S vapor had a significant sulfuration effect on the surface of the CZTSSe thin films post-etching. The surface defects of the CZTSSe film were passivated by the sulfur element entering the film by sulfuration. Moreover, the bandgap of the CZTSSe thin films was improved. The efficiency of the solar cell device increased by 1.72 % with a plasma etching duration of 5 min and (NH4)2S vaporization treatment of 15 min. This study proposes a novel approach that employs surface passivation techniques to enhance the efficiency of CZTSSe thin film solar cells.

Fostering Charge Carrier Transport and Absorber Growth Properties in CZTSSe Thin Films with an ALD-SnO2 Capping Layer.

The present study demonstrates that precursor passivation is an effective approach for improving the crystallization process and controlling the detrimental defect density in high-efficiency Cu2ZnSn(S,Se)4 (CZTSSe) thin films. It is achieved by applying the atomic layer deposition (ALD) of the tin oxide (ALD-SnO2) capping layer onto the precursor (Cu-Zn-Sn) thin films. The ALD-SnO2 capping layer was observed to facilitate the homogeneous growth of crystalline grains and mitigate defects prior to sulfo-selenization in CZTSSe thin films. Particularly, the CuZn and SnZn defects and deep defects associated with Sn were effectively mitigated due to the reduction of Sn2+ and the increase in Sn4+ levels in the kesterite CZTSSe film after introducing ALD-SnO2 on the precursor films. Subsequently, devices integrating the ALD-SnO2 layer exhibited significantly reduced recombination and efficient charge transport at the heterojunction interface and within the bulk CZTSSe absorber bulk properties. Finally, the CZTSSe device showed improved power conversion efficiency (PCE) from 8.46% to 10.1%. The incorporation of ALD-SnO2 revealed reduced defect sites, grain boundaries, and surface roughness, improving the performance. This study offers a systematic examination of the correlation between the incorporation of the ALD-SnO2 layer and the improved PCE of CZTSSe thin film solar cells (TFSCs), in addition to innovative approaches for improving absorber quality and defect control to advance the performance of kesterite CZTSSe devices.

Analysis of optical and electrical properties in CZTSSe thin film solar cells through the 2d theoretical modeling

In this work, a 2D simulator (i.e., SILVACO ATLAS simulator) was used for modeling the Cu2ZnSn(S, Se)4 (CZTSSe) thin film solar cells. This simulation study mainly focused on the influence of the electrical and optical parameters that describe the electrical properties of each layer and the absorbed radiation in the heterostructure. These two parameters are analyzed and optimized to get as high of an efficiency as possible. It was characterized by means of the simulation that the effect of the electrical and optical parameters on the solar cell output parameters (VOC,JSC,FF,andη) was studied. The other parameters, such as temperature, bandgap, mobility, and thickness, were also varied in this simulative study for optimizing the device performance. The second record efficiency of 12.6 % was observed for the CZTSSe thin film solar cell (TFSC). This obtained result was compared with the results attained from the SCAPS-1D simulation as well as the second record efficiency for CZTSSe TFSC. Moreover, the Haze function was used to characterize the transmittance and diffuse reflectance in the rough interfaces between the layers of the solar cell. The Haze function utilized the input data like roughness and correction prefactors, which mainly impact the root-mean-square interface roughness (σrms) value by studying the External Quantum Efficiency curve variation. After analyzing these parameters, the efficiency was slightly improved to 13.02 %. Therefore, theoretical modeling could be beneficial to design highly efficient devices without utilizing experimental resources.

Promoting effect of lanthanum doping on photovoltaic performance of CZTSSe solar cells.

A large open-circuit voltage (VOC) deficit is the major challenge hindering the efficiency improvement of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Cation substitution, or doping, is usually an effective strategy to achieve carrier regulation and improve efficiency. In this work, we developed a rare-earth element lanthanum (La) doped CZTSSe thin-film solar cell by directly introducing La3+ ions into the CZTS precursor solution. Such a proposed La doping approach could effectively enhance light harvesting, adjust the bandgap, and increase the electron diffusion length. Furthermore, appropriate concentrations of La doping can reduce harmful defect cluster. Benefiting from the La doping, the VOC significantly increases from 431 to 497 mV. Consequently, the power conversion efficiency is enhanced significantly from 6.54% (VOC = 431 mV, JSC = 25.50 mA/cm2, FF = 58.28%) for the reference cell to 10.21% (VOC = 497 mV, JSC = 35.20 mA/cm2, FF = 58.41%) for the optimized La-doped cell. This research provides a new direction for enhancing the performance of CZTSSe cells, offering promising prospects for the future of CZTSSe thin-film solar cells.

Achieving high open-circuit voltage in efficient kesterite solar cells via lanthanide europium ion induced carrier lifetime enhancement

Short carrier lifetimes is a key challenge limiting the open-circuit voltage (VOC) and power conversion efficiency (PCE) of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. In this work, for the first time, lanthanide europium (Eu) ions have been introduced into Ag-incorporated CZTSSe absorber layer, which can modify the selenization reaction pathway during the initial selenization process, leading to high-quality (Ag, Eu)-CZTSSe absorber with large compact crystal grains and benign surface potential fluctuations. This innovative absorber engineering can also optimize defects dynamics with less detrimental defects and defects-assisted non-radiative recombination. Thus, significantly enhanced minority carrier lifetimes from 0.97 to 3.15 ns can be achieved, representing one of the top values among various bulk and/or interface engineering treated CZTSSe. The champion CZTSSe thin-film solar cell exhibits an impressive VOC of 545.6 mV, accompanied with a stimulating increase in PCE from 10.68% to 13.30%. These findings underscore the potential of lanthanide cation doping to drive significant advancements in CZTSSe photovoltaic technology, and therefore promoting its further development and future applications.

Current Status and Future Prospects of Kesterite Cu2ZnSn(S,Se)4(CZTSSe) Thin Film Solar Cells Prepared via Electrochemical Deposition

AbstractThe fabrication of kesterite Cu2ZnSn(S,Se)4(CZTSSe) thin‐film solar cells using the electrochemical deposition (ED), which is valued for its industrial feasibility, offers a cost‐effective and environmentally friendly approach to the carbon‐free and clean energy production. However, the reported power conversion efficiency of approximately 10 % for electrodeposited CZTSSe thin‐film solar cells is lower compared to the alternative methods like sputtering and spin‐coating, which is mainly attributed to the phase inhomogeneity and the rough morphology generated during the ED process. Ensuring the microscopic and macroscopic uniformity of the electrodeposited films is crucial for the improvement of the film quality and the device performances. In this review, strategies to address these challenges including the intrinsic film control such as the deposition mode, pH, concentration of metal ions, and complexing agents, as well as the extrinsic approaches such as doping, substitution of metal elements, and the introduction of interfacial layers. In addition, the prospects for the electrochemically deposited CZTSSe solar cells were presented, focusing on the promising applications in tandem, flexible, and solar water‐splitting devices. Finally, this review will provide technical insights into the ED process for preparing CZTSSe solar cells, outlining a perspective for the future development of highly efficient CZTSSe thin film solar cells.

Proton radiation hardness and its loss mechanism of Cu2ZnSn(S,Se)4 thin film solar cells

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) have proven to be promising materials for photovoltaic applications. The current state-of-the-art CZTSSe photovoltaic device improvements in efficiency have been hampered by difficulties in increasing open circuit voltages (VOC). Herein, we thoroughly analyzed the proton irradiation hardness and its loss mechanism of CZTSSe thin film solar cells. The efficiency loss mechanism of the CZTSSe solar cell is proposed by systematically studying the device performance, optical and electrical properties, and distribution changes in elements upon proton irradiation. It was revealed that proton-irradiation-induced element diffusion in device affects the absorber properties and CdS/CZTSSe heterojunction dramatically and deteriorates the performance of the device. Finally, the main factors that may affect device performance of CZTSSe solar cells are highlighted, and the CZTSSe solar cells also demonstrate a remarkable radiation hardness.

Improving the Device Performance of CZTSSe Thin-Film Solar Cells via Indium Doping.

Cation incorporation emerges as a promising approach for improving the performance of the kesterite Cu2ZnSn(S,Se)4 (CZTSSe) device. Herein, we report indium (In) doping using the chemical bath deposition (CBD) technique to enhance the optoelectronic properties of CZTSSe thin-film solar cells (TFSCs). To incorporate a small amount of the In element into the CZTSSe absorber thin films, an ultrathin (<10 nm) layer of In2S3 is deposited on soft-annealed precursor (Zn-Sn-Cu) thin films prior to the sulfo-selenization process. The successful doping of In improved crystal growth and promoted the formation of larger grains. Furthermore, the CZTSSe TFSCs fabricated with In doping exhibited improved device performance. In particular, the In-CZTSSe-2-based device showed an improved power conversion efficiency (PCE) of 9.53%, open-circuit voltage (Voc) of 486 mV, and fill factor (FF) of 61% compared to the undoped device. Moreover, the small amount of In incorporated into the CZTSSe absorber demonstrated reduced nonradiative recombination, improved carrier separation, and enhanced carrier transport properties. This study suggests a simple and effective way to incorporate In to achieve high efficiency and low Voc loss.

Effects of bending stress on structural and electrical properties of flexible CZTSSe thin film solar cells

Effects of bending stress on structural and electrical properties of flexible CZTSSe thin film solar cells

Effects of defect density, minority carrier lifetime, doping density, and absorber-layer thickness in CIGS and CZTSSe thin-film solar cells

Effects of defect density, minority carrier lifetime, doping density, and absorber-layer thickness in CIGS and CZTSSe thin-film solar cells

Insights into the Efficiency Improvement for CZTSSe Solar Cells with over 12% Efficiency via Ga Incorporation

AbstractSuppressing the band tailing and nonradiative recombination caused by massive defects and defect clusters is crucial for mitigating open‐circuit voltage (Voc) deficit and improving the device performance of CZTSSe thin film solar cells. Cation substitution is one of the most commonly used strategies to address the above issues. The latest world record efficiency of 13.0% is obtained through this strategy (Ag substitution for Cu). Nevertheless, the importance of the approach to implementing metallic ion doping is easily overlooked by researchers. Here, different approaches are adopted to realize Ga doping and the differences in the efficacy and mechanism are thoroughly investigated. It is found that the secondary phase easily emerged when the physical‐based method is employed, and thus challenging to regulate the doping effect. In the case of the chemical‐based method, Ga doping can enlarge the depletion region widthand lower the defect activation energyand Urbach energy. Furthermore, GaSn defects located at grain boundaries can expand the energy band bending between GBs and grain interiors (GIs), thereby suppressing the deep defect states and nonradiative recombination. Consequently, power conversion efficiency as high as 12.12% with a Voc of 522 mV is achieved at 2% Ga doping.

High photovoltaic efficiency CZTSSe thin film solar cells obtained by Li doping in air

Alkali metal doping is considered as an effective strategy in the pathway of improving the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic materials. In this paper, Li is successfully doped into CZTSSe films in air and high efficiency devices are obtained. By X-ray diffraction and scanning electron microscopy, it can be found that the crystalline quality of CZTSSe films after Li doping is effectively improved and full and dense absorber layer crystals are obtained. In addition, TRPL also shows that the carrier lifetime of CZTSSe by doping with Li is significantly enhanced. Lithium-doped CZTSSe thin-film solar cells finally achieve a high efficiency of 9.84%. This Li doping route with simple process and superior device performance obtained provides a new idea for further development of element-rich and non-toxic CZTSSe thin film materials.

Crystallization mechanism and defect passivation of Cu2ZnSn(S,Se)4 thin film solar cells via in situ potassium doping

Alkali metal doping has achieved prominent results in Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells. In this paper, in situ K-doped CZTSSe thin film solar cells were prepared by magnetron sputtering with a K-containing CZTS target.

Synthesis and investigation of solution-processed Bi-doped Cu2ZnSn(S, Se)4 thin-film solar cells

Surface morphology plays a crucial role in influencing the film quality and photoelectric conversion efficiency (PCE) of a Kesterite Cu 2 ZnSn(S, Se) 4 (CZTSSe) solar cell. Herein, the bismuth (Bi) doping strategy to improve the surface morphology of the solution-processed CZTSSe film for high solar cell efficiency is reported. With a two-step selenization strategy to facilitate the Bi-doped CZTSSe (CZTBiSSe) phase formation, improving the crystalline quality of the absorber, increasing the carrier mobility, and reducing the band tailing, a cell efficiency of 6.94% has been achieved. These results demonstrate the significance of Bi doping into CZTSSe to improve the device's performance. This work offers new insights into the effects of Bi doping on CZTSSe via a solution-processed approach and provides a deeper understanding of the origin of the efficiency improvement of Bi-doped CZTSSe thin film solar cells. • A new method to improve Voc and PCE of CZTSSe solar cell by Bi doping is put forward. • This is the first report on solution-processed CZTBiSSe using two-step selenization. • This study shows hopeful character of Bi in increasing the Voc of CZTSSe solar cell. • Bi doping can improve crystal quality and decrease Sn Zn antisite defect states. • It is proved that Bi-doped CZTSSe is a promising band-gap tunable absorption layers.

An innovative design of arrays-interpenetrated CZTSSe/MoO3 back interfacial contacts for improving the solar cell performance

It is widely known that the challenge of making good electrical contact at the back electrode interface will always follow us for high-efficient kesterite-type CZTSSe thin-film solar cells. Aiming at clarifying the correlation of device performance on the micro-structure of back interface, we come up with a new fresh design that introducing in-situ anodized MoO 3 porous arrays with regulated structural parameters acts as the back interfacial contact. Regards the such array-structures of interpenetrated CZTSSe and MoO 3 , the study reveals that the overall device performance is closely related to the micro-structure of the MoO 3 interface layer, and the optimized device efficiency can be improved to 9.00% from 6.31% (Ref. Mo-based cells), having a 32% increased J SC together with a 64% increase in FF. The performance improvement mechanism is analyzed in details. The interesting preliminary finding would indicate that the new strategy is very effective to form reliable electrical contact at the back interface for high-efficient CZTSSe solar cells. • New design of interpenetrated CZTSSe/MoO 3 arrays for innovative interfacial contact of CZTSSe solar cells. • Nearly 43% increase of efficiency from 6.31% to 9.00% is achieved. • Increase of J SC from 25.49 to 33.63 mA/cm 2 and FF from 60.4% to 63.65%. • Potential for revealing the effect of back contact structure on device performance.

Rear interface engineering via a facile oxidation process of Mo back contact for highly efficient CZTSSe thin film solar cells

The kesterite-based Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) are promising absorber material for next-generation TFSCs technology because they exhibit earth-abundant, non-toxic elements and favorable optoelectronic properties. However, the progress and device performance development in CZTSSe TFSCs were limited because of unstable rear interface characteristics near the absorber/molybdenum (Mo) interface, which causes large open-circuit voltage loss. In this study, we report the rear interface engineering of CZTSSe TFSCs to improve device performance by introducing an amorphous thin MoOx intermediate layer by a facile oxidation process. We observed that (i) an amorphous thin MoOx intermediate layer can effectively control the rear interface properties (i.e., inhibiting the formation of Mo(S,Se)2 interfacial layers and voids at CZTSSe/Mo interface) and (ii) the improved device performance in CZTSSe TFSCs with oxidation (w-oxidation) is attributed primarily to the dramatically decreased shunt conductance, formation of large-sized grains within CZTSSe absorber layer, and improved rear interface characteristics. This study presents a simple and low-temperature oxidation process for rear interface engineering of highly efficient kesterite CZTSSe-based TFSCs.

Simulation of heat generation from defects at different energy levels in CZTSSe thin film solar cells

Simulation of heat generation from defects at different energy levels in CZTSSe thin film solar cells

The Degradation of Cu2ZnSn(S,Se)4 Kesterite Thin Film Solar Cells Induced by Proton Radiation

AbstractAiming at the current bottleneck of Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells, an experimental analysis of the performance and loss mechanism of CZTSSe thin film solar cells upon proton radiation exposure is presented. In order to deduce the important cell parameters, the environment of the cells is simulated by subjecting the devices to 200 keV proton irradiation with fluences from 1 × 1010 to 1 × 1017 cm‐2. It is found that the damage constants are sensitive to the elemental diffusion at heterojunction and Na redistribution in device. The incidence of the proton can lead to bandgap, tails fluctuations, and Urbach energy changes in the cells those directly impact defects and structural disorder in CZTSSe material thereby the device performance. The time‐resolved photoluminescence results show that the carrier lifetime is also very sensitive to the distribution of interface elements, especially Na, Cd, and S. These findings may provide new ideas for solving the VOC deficit of CZTSSe solar cells. From this work, it can be also suggested that the CZTSSe thin film solar cells are robust to proton irradiation and have the potential for future space applications.

Enhancing carrier transport in flexible CZTSSe solar cells via doping Li strategy

The passivation of non-radiative states and inhibition of band tailings are desirable for improving the open-circuit voltage (Voc) of CZTSSe thin-film solar cells. Recently, alkali metal doping has been investigated to passivate defects in CZTSSe films. Herein, we investigate Li doping effects by applying LiOH into CZTSSe precursor solutions, and verify that carrier transport is enhanced in the CZTSSe solar cells. Systematic characterizations demonstrate that Li doping can effectively passivate non-radiative recombination centers and reduce band tailings of the CZTSSe films, leading to the decrease in total defect density and the increase in separation distance between donor and acceptor. Fewer free carriers are trapped in the band tail states, which speeds up carrier transport and reduces the probability of deep-level defects capturing carriers. The charge recombination lifetime is about twice as long as that of the undoped CZTSSe device, implying the heterojunction interface recombination is also inhibited. Besides, Li doping can increase carrier concentration and enhance build-in voltage, leading to a better carrier collection. By adjusting the Li/(Li + Cu) ratio to 18%, the solar cell efficiency is increased significantly to 9.68% with the fill factor (FF) of 65.94%, which is the highest FF reported so far for the flexible CZTSSe solar cells. The increased efficiency is mainly attributed to the reduction of Voc deficit and the improved CZTSSe/CdS junction quality. These results open up a simple route to passivate non-radiative states and reduce the band tailings of the CZTSSe films and improve the efficiency of the flexible CZTSSe solar cells.