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Excellent morphology and low harmful defect states of the absorber layer are essential to fabricate the high‐performance Cu2ZnSn(S, Se)4 (CZTSSe) devices. Herein, the annealing time of precursor films in air is proved to have much impact on the quality of absorber layer and the performance of devices. Appropriately extending the air‐annealing time can promote the diffusion of Na into films and O absorption on the surface of precursor films, boost the growth of crystal grain, and lessen the harmful defect density and band‐tailing states of absorber. The appropriate extension of air‐annealing time also regulates the electrical properties of the absorber. The efficiency of CZTSSe devices is enhanced from 6.92% (1 min) to 10.1% (7 min), with the decreased VOC, Def. These enhanced properties demonstrate that regulating the air‐annealing time of precursor films can be a simple and direct way for improving the performance of CZTSSe devices. [ABSTRACT FROM AUTHOR]

Semitransparent perovskite solar cells (ST‐PSCs) are highly promising for application in building‐integrating photovoltaics (BIPVs) due to their potential in tunable transparency and color. However, the comprehensive performance of ST‐PSCs falls quite short of the ideal requirements for BIPV. Herein, more attention is to review how to balance transparency and power conversion efficiency for ST‐PSCs. Optimizing transparent electrodes and the active layers are interesting strategies to achieve the transparency required by devices. In addition, to obtain color ST‐PSCs, tuning the bandgap of perovskite layers and designing the optical structure of the electrode are effective strategies. Last but not least, three significant optical evaluation indexes of ST‐PSCs are described in the supporting information: average visible transmittance, color rendering index, and light utilization efficiency. [ABSTRACT FROM AUTHOR]

In order to fabricate nickel oxide (NiOX)-based perovskite solar cells with high efficiency and stability, adverse reaction and lattice mismatch are two urgent problems to be overcome. In this respect, interface engineering was carried out by multi-layer passivation NiOX HTLs (NiOX/2PACz/Poly-TPD/PEAI) to provide optimized interface contact between NiOX and perovskite, ameliorate band alignment, and saturate the defect states. Application of 2PACz avoids direct contact of the hydroxyl groups (which causes degeneration of a device), improves conductivity, and reduces interfacial defects. The poly-TPD modification can provide an appropriate band alignment at the interface of NiOX/perovskite. PEAI was used to modify the Poly-TPD surface, and its −NH3 group can passivate unbonded Pb ions of perovskite. Thus, compared with previously reported single-function passivation materials, the multilayer passivation proposed in this paper integrates multiple functions. As a result, the NiOX/2PACz/Poly-TPD/PEAI-based wide bandgap PSCs obtain a champion power conversion efficiency (PCE) of 20.21% and maintain over 95% of their initial PCE values after storage in a nitrogen atmosphere for 1000 h. This finding provides a practical approach for fabricating high-performance regular PSCs with NiOX-based HTLs and supports their commercialization. [ABSTRACT FROM AUTHOR]

Although perovskite solar cells (PSCs) based on SnO2 have reached a power conversion efficiency (PCE) over 25%, large-scale fabrication remains the main obstacle to the commercialization of PSCs. Therefore, considering the process compatibility, low-temperature processing and large-area fabrication technologies have received widespread attention as those are ideal for upscaling of single and tandem devices. Herein, we demonstrated an effective atomic layer deposition (ALD) process by using H2O2 as an oxygen source and the deposition temperatures can be lowered up to 50 °C due to the high activity of H2O2. The low temperature deposition enables conformal coverage of the substrate and results in a pinhole-free film with high optical transmittance, excellent electron extraction properties, and large area uniformity. Notably, a high PCE of 20.70% is achieved for single junction PSCs based on ALD-SnO2 (50 °C). When the ALD-SnO2 applied to p-i-n structure perovskite/silicon heterojunction tandem solar cell, an efficiency of 26.67% was obtained. The results demonstrate the potential of the low-temperature ALD processed metal oxide for large-scale manufacturing of optoelectronic devices with competitive performances. [ABSTRACT FROM AUTHOR]

In this work, Cu2ZnSnS4 (CZTS) precursor films were deposited using a water-based solution approach. Subsequently, selenization was performed at different temperatures in the range of 480–610 °C to prepare Cu2ZnSn(S,Se)4 (CZTSSe) absorber-layer films. The effects of the selenization temperature on the crystallinity, structure, morphology, and photoelectric properties of CZTSSe thin films, as well as the performance of solar cells constructed using these films, were systematically studied. The absorber-layer films selenized at different temperatures all formed pure-phase CZTSSe and had basically the same film thickness. It was found that application of an optimal selenization temperature can enhance the crystallinity, crystal grain size, and mobility and reduce the resistivity of CZTSSe films. Selenization at 550 °C resulted in the largest grain size (∼μm), the highest crystallinity, the highest mobility (4.29 cm2 V−1 s−1), the lowest resistivity (3.13 × 102 Ω cm), the thinner fine-grained layer, a bandgap value of 1.21 eV, and a Cu-poor, Zn-rich elemental composition [Cu/(Zn + Sn) = 0.85 and Zn/Sn = 1.16]. The power-conversion efficiency was improved from 3.04% in a CZTSSe cell device with an absorber layer selenized at 480 °C to 4.69% in a film selenized at 550 °C. This was mainly due to the improvement of the crystallinity, crystal grain growth, and reduction of the fine-grained layer of the CZTSSe film. These results show that optimizing the selenization temperature is essential for enhancing the performance and the ultimate device efficiency of CZTSSe absorber layers prepared using a water-based solution approach. [ABSTRACT FROM AUTHOR]

Cu 3 V(S, Se) 4 material is considered as a novel potential absorber of thin film solar cells due to its excellent properties. In this work, it is the first time that Cu 3 V(S, Se) 4 thin film solar cells are prepared by solution method, and the preparation process of fine absorbers is explored. The combination of air-baking and selenization processes boosts the excellent Cu 3 V(S, Se) 4 absorber. The optimal air-baking and selenization condition is confirmed as 360 °C for 20 min and 560 °C for 30 min, respectively. And the highest photoelectric conversion efficiency (PCE) of Cu 3 V(S, Se) 4 solar cells is 1.68 %. This is the first report on the solution preparation of Cu 3 V(S, Se) 4 thin film solar cells, and it is believed that performance of Cu 3 V(S, Se) 4 solar cells will be optimized by improving the preparation process in the future. [ABSTRACT FROM AUTHOR]

The CZTSSe absorber layer prepared with DMSO exhibits extensive cavities at its bottom, and a prominent double-layer structure is frequently observed within the CZTSSe absorber synthesized using DMF, both of which have a detrimental impact on the device performance. In this paper, an alternate spin-coating process using DMSO and DMF solvent systems is proposed, which eliminates the double-layer structure of CZTSSe and reduces the number of cavities at the bottom of the absorber layer, thereby enhancing its overall quality. This method outperforms the traditional single-solution spin-coating technique by combining the advantages of two solvent systems, allowing for the preparation of an ideal CZTSSe film without disturbing the elemental ratio, ultimately resulting in a single-layer absorber composed of large grains. After three repetitions of an identical alternate spin-coating process, the average grain size of the absorber layer increased from 0.83 to 1.21 μm. This innovative process leads to a reduction in carrier recombination and an improvement in the short-circuit current density, ultimately raising the photoelectric conversion efficiency from 7.40% to 8.88%. • Modified the conventional spin-coating process in the preparation of CZTSSe absorber layers. • Presented a method combining the benefits of a dual-solution system approach. • The alternate spin-coating process using DMSO and DMF solvent systems improved the morphology of absorber. [ABSTRACT FROM AUTHOR]

Interfaces quality have always been considered the key factors in the fabrication of efficient Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells, and harmful defects at the interface can significantly reduce the performance of the device. Here, we propose a dual passivation strategy by adding Na to the surface of the absorber layer (CZTSSe) to passivate the CZTSSe/CdS interface and treating the buffer layer (CdS) using ultraviolet (UV) irradiation to passivate the CdS/ZnO interface. Due to the Na doping passivation, the absorber surface conductivity increases while the roughness decreases and detrimental defects that can lead to nonradiative recombination are reduced. The power conversion efficiency (PCE) of the cell is improved by about 1 percentage point by Na passivation. The contributions of open-circuit voltage (V oc), short-circuit current density (J sc), and fill factor (FF) to the improvement of PCE have been quantified as 50.64%, −5.58%, and 54.94%, indicating that Na doping can significantly boost V oc and FF. UV-ozone passivation reduces residual carbon organics in the CdS buffer layer, weakens carrier recombination, allows for more light absorption, and widens the depletion region, which favors efficient carrier collection. The estimated contribution of V oc , J sc , and FF to the PCE of the device is 8.78%, 119.59%, and −28.37%, respectively, demonstrating that UV-ozone passivation can significantly improve the J sc of the device. The two passivation strategies complement each other's advantages and achieve a synergistic effect. Our prepared champion device exhibits a PCE of 10.69% and remarkable long-term stability. [Display omitted] • Innovative dual passivation strategy proposed for CZTSSe/CdS and CdS/ZnO interfaces. • Sodium passivation of the absorber surface can significantly boost the V oc and FF. • UV-ozone passivation can effectively reduce residual carbon organics in the CdS buffer layer. • Under the dual passivation strategy, the PCE of CZTSSe device is improved from 8.07% to 10.69%. [ABSTRACT FROM AUTHOR]

The absorbers of kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) that have undergone rapid thermal process (RTP) selenization typically exhibit a double-layer structure, with a fine crystal layer at the bottom, which degrades the performance of devices. We propose an efficient strategy for actively constructing the double-layer absorber to improve the quality of the small grains in the bottom layer. Compared to traditional methods, this method ensures uniform element distribution, particularly for Se element, and enables a more desirable Cu-poor and Zn-rich composition with a Zn/Sn ratio closer to the standard stoichiometric ratio, resulting in a reduction in harmful internal defects. This strategy eliminates small grains at the bottom and decreases grain boundary formation, resulting in a dense double-layer structure. The high-quality CZTSSe absorber not only reduces carrier recombination during back transmission, further reducing reverse saturation current (J 0) and increasing optical current density (J L), but also enhances shunt resistance (R sh) and decreases series resistance (R S). The estimated contribution percent for PCE improvement due to changes in J L , J 0 , R sh , R S , and A are 17.20 %, 120.01 %, 1.15 %, 6.50 %, and -44.86 %, respectively. Ultimately, the highest photoelectric conversion efficiency (PCE) increased from 8.73 % to 10.49 %, and device uniformity improved considerably. This study highlights the significance of optimizing the microstructure of CZTSSe absorber layer in enhancing the performance of CZTSSe solar cells, and will provide guidance for producing high-quality CZTSSe absorber layers. • Actively construct the double-layer CZTSSe absorber. • The uniform distribution of elements with the better ratio of Cu-poor and Zn-rich. • Eliminate the small bottom grains forming the dense double-layer structure. • Decrease the carrier recombination in the back transmission process. • Optimize the J L J 0 , R s , and R sh for improving the performance of devices. [ABSTRACT FROM AUTHOR]

Homogeneous large-grain structure of Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber has been proven to be one of the conditions for high photoelectric conversion efficiency (PCE) devices. In this work, we explored that the different choices of selenization temperature had influences on the morphology, crystallinity, and electric properties of CZTSSe absorbers. With the selenization temperature of 540°C, the single-layer large-grain structure of CZTSSe absorber could be prepared, and grain boundary defects could be reduced. 540°C is also the transition temperature of the substrate (Soda-lime glass, SLG) of devices. The SLG softens at the transition temperature and the structure is unstable, resulting in Na entering CZTSSe better at 540°C than at a lower selenization temperature. The suitable Na diffusion can promote the growth of grains and help the corresponding device possesses the highest PCE (9.38%), which is also increased by ∼85% than ones prepared under the lower selenization temperature (PCE stayed at 5%). Therefore, the appropriate selenization conditions for the high-efficiency devices also need to consider the properties of the substrates. These conclusions also propose the new point on obtaining the optimal selenization condition for the high-performance CZTSSe devices. • The transition temperature (540°C) of the glass can be the optimal selenization temperature of the CZTSSe absorber. • The optimal Na content of the soda-lime glass can enter CZTSSe absorber under the glass transition temperature. • Under glass transition temperature (540°C), the photoelectric conversion efficiency of CZTSSe device is improved from 5% to 9.38%. [ABSTRACT FROM AUTHOR]

Two-step selenization process has been proved to control Cu 2 ZnSn(S,Se) 4 (CZTSSe) crystallization growth, helping to fabricate a homogeneous large-grain structure of CZTSSe absorber. The two-step selenization process is usually composed of the low-temperature nucleation (LT) and high-temperature grain growth reaction (HT) processes. Here, an exploration of optimizing the annealing conditions at each step in the two-step process is reported to obtain the excellent structure of ionic liquid solution based Cu 2 ZnSn(S,Se) 4 absorber, boosting performance of the solar cell. Based on the basic requirement of an absorber candidate for solar cells (the compact films), three effective kinds of two-step process are confirmed (LT400–10&HT540–10, LT400–10&HT550–10, and LT400–10&HT560–10). We further explore the other properties of sample prepared by one-step and these three kinds of two-step process, respectively, and the optimal two-step process can be identified as LT400–10&HT550–10, which also confirms a homogeneous large-grain structure of CZTSSe absorber. Finally, CZTSSe solar cell with the highest efficiency of 9.24% can be achieved, which can be improved 67% than one by one-step annealing process (5.54%). • The detail optimization of annealing conditions at each step in the two-step selenization process is explored. • Homogeneous large-grain structure of Cu 2 ZnSn(S,Se) 4 absorber can be fabricated at the optimal two-step selenization condition. • The best efficiency of corresponding device can be obtained to be 9.24%, increased by 67% compared with one-step process. [ABSTRACT FROM AUTHOR]