Building a Charge Transfer Bridge between g-C3N4 and Perovskite with Molecular Engineering to Achieve Efficient Perovskite Solar Cells.

Effective defect passivation and efficient charge transfer within polycrystalline perovskite grains and corresponding boundaries are necessary to achieve highly efficient perovskite solar cells (PSCs). Herein, focusing on the boundary location of g-C3N4 during the crystallization modulation on perovskite, molecular engineering of 4-carboxyl-3-fluorophenylboronic acid (BF) on g-C3N4 was designed to obtain a novel additive named BFCN. With the help of the strong bonding ability of BF with both g-C3N4 and perovskite and favorable intramolecular charge transfer within BFCN, not only has the crystal quality of perovskite films been improved due to the effective defects passivation, but the charge transfer has also been greatly accelerated due to the formation of additional charge transfer channels on the grain boundaries. As a result, the champion BFCN-based PSCs achieve the highest photoelectric conversion efficiency (PCE) of 23.71% with good stability.

Break through the Steric Hindrance of Ionic Liquids with Carbon Quantum Dots to Achieve Efficient and Stable Perovskite Solar Cells.

Overcoming the negative impact of residual ionic liquids (ILs) on perovskite films based on an in-depth understanding of chemical interactions between ionic liquids and preparing perovskite precursor solutions is a great challenge when aiming to simultaneously achieve long-term stability and high efficiency within IL-based perovskite solar cells (PSCs). Herein, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), a type of IL, was introduced into the perovskite precursor solution, and carbon quantum dots (CQDs) were further introduced into the antisolvent to enhance the photovoltaic properties of PSCs. Both ILs and CQDs synergistically manipulate the crystallization process and passivate defects to obtain high-quality perovskite films. Besides serving as passivation sites to strengthen the collaboration between additives and perovskite materials, the cointroduction of CQDs further promotes the carrier transport process since it not only provides carrier channels at grain boundaries but also forms better energy alignment, which effectively overcomes the charge transfer loss caused by the steric hindrance of ILs. Based on such a synergistic effect of ILs and CQDs, the n-i-p MAPbI3-based PSCs achieve the highest efficiency of 20.84% with improved stability. This simple and low-cost synergistic integration method will subsequently provide direction for optimizing ILs to improve the photovoltaic performance of PSCs.

Managing intermediate phase transition of perovskite film with gearbox-like molecule for efficient and stable solar cells.

The smooth and dense light-absorbing layer is an essential factor in polycrystalline solar cells to achieve high photovoltaic performance, while it remains challenging in perovskite solar cells because of the difficulty balancing the speed of crystal nucleation and growth in a solution way. Here, we explored a perovskite nucleation/growth compatible model via manipulating the intermediate complex induced by n-hexylamine (NHA) molecule, guiding us to adjustments perovskite nucleation and growth process. We found that the NHA can act as a gearbox-like molecule to sequentially reduce the perovskite nucleation barrier, promote the nucleation velocity, and retard the perovskite growth simultaneously to obtain uniform perovskite films; correspondingly, this modulation also yields the buried interface with fewer voids and low defects density. In addition, the hydrophobic NHA with long alkyl chain improves the moisture tolerance of the perovskite. The treated solar cell power conversion efficiency was 21.91 %. Importantly, in âˆ¼ 70 % humidity at 25 °C for 30 days, the efficiency of the device declined less than 5 %, exhibiting a good stability performance.

Modulating Crystallization and Defect Passivation by Butyrolactone Molecule for Perovskite Solar Cells.

The attainment of a well-crystallized photo-absorbing layer with minimal defects is crucial for achieving high photovoltaic performance in polycrystalline solar cells. However, in the case of perovskite solar cells (PSCs), precise control over crystallization and elemental distribution through solution processing remains a challenge. In this study, we propose the use of a multifunctional molecule, α-amino-γ-butyrolactone (ABL), as a modulator to simultaneously enhance crystallization and passivate defects, thereby improving film quality and deactivating nonradiative recombination centers in the perovskite absorber. The Lewis base groups present in ABL facilitate nucleation, leading to enhanced crystallinity, while also retarding crystallization. Additionally, ABL effectively passivates Pb2+ dangling bonds, which are major deep-level defects in perovskite films. This passivation process reduces recombination losses, promotes carrier transfer and extraction, and further improves efficiency. Consequently, the PSCs incorporating the ABL additive exhibit an increase in conversion efficiency from 18.30% to 20.36%, along with improved long-term environmental stability. We believe that this research will contribute to the design of additive molecular structures and the engineering of components in perovskite precursor colloids.

N-glycosylation by N-acetylglucosaminyltransferase IVa enhances the interaction of integrin ß1 with vimentin and promotes hepatocellular carcinoma cell motility.

N-glycosylation has been revealed to be tightly associated with cancer metastasis. As a key transferase that catalyzes the formation of ß1,4 N-acetylglucosamine (ß1,4GlcNAc) branches on the mannose core of N-glycans, N-acetylglucosaminyltransferase IVa (GnT-IVa) has been reported to be involved in hepatocellular carcinoma (HCC) metastasis by forming N-glycans; however, the underlying mechanisms are largely unknown. In the current study, we found that GnT-IVa was upregulated in HCC tissues and positively correlated with worse outcomes in HCC patients. We found that GnT-IVa could promote tumor growth in mice; notably, this effect was attenuated after mutating the enzymatic site (D445A) of GnT-IVa, suggesting that GnT-IVa regulated HCC progression by forming ß1,4GlcNAc branches. To mechanistically investigate the role of GnT-IVa in HCC, we conducted GSEA and GO functional analysis as well as in vitro experiments. The results showed that GnT-IVa could enhance HCC cell migration, invasion and adhesion ability and increase ß1,4GlcNAc branch glycans on integrin ß1 (ITGB1), a tumor-associated glycoprotein that is closely involved in cell motility by interacting with vimentin. Interruption of ß1,4GlcNAc branch glycan modification on ITGB1 could suppress the interaction of ITGB1 with vimentin and inhibit cell motility. These results revealed that GnT-IVa could promote HCC cell motility by affecting the biological functions of ITGB1 through N-glycosylation. In summary, our results revealed that GnT-IVa is highly expressed in HCC and can form ß1,4GlcNAc branches on ITGB1, which are essential for interactions with vimentin to promote HCC cell motility. These findings not only proposed a novel mechanism for GnT-IVa in HCC progression but also revealed the significance of N-glycosylation on ITGB1 during the process, which may provide a novel target for future HCC therapy.

Systematic review of ethnomedicine, phytochemistry, and pharmacology of Cyperi Rhizoma.

Cyperi Rhizoma (CR) is the dry rhizome of Cyperus rotundus L., a Cyperaceae plant. It has a long history of clinical medication and is known as the "holy medicine" of gynecology. CR smells sweet and bitter. It has the effect of soothing the liver and relieving depression, regulating qi, regulating meridian and relieving pain. It can be used to treat liver qi stagnation, chest pain, spleen and stomach qi stagnation, hernia pain, irregular menstruation and other diseases. At present, the main chemical constituents isolated from CR are volatile oil, flavonoids and terpenes. Modern pharmacological studies have shown that CR has a wide range of pharmacological activities, including antidepressant, hypoglycemic, antioxidant, anti-inflammatory, antipyretic and analgesic effects. In this paper, the botany, traditional application, phytochemistry, pharmacological effects, processing and other aspects of CR are reviewed. At the same time, the shortcomings of current research of CR are discussed in depth, and the possible solutions are put forward in order to find a breakthrough point for future research of CR.

Insight into the Effect of Selenization Temperature for Highly Efficient Ni-Doped Cu2ZnSn(S,Se)4 Solar Cells.

Cu2Ni0·05Zn0·95Sn(S,Se)4 (CNZTSSe) films were synthesized on Mo-coated glass substrates by the simple sol-gel means combined with the selenization process, and CNZTSSe-based solar cells were successfully prepared. The effects of selenization temperature on the performance and the photoelectric conversion efficiency (PCE) of the solar cells were systematically studied. The results show that the crystallinity of films increases as the selenization temperature raises based on nickel (Ni) doping. When the selenization temperature reached 540 °C, CNZTSSe films with a large grain size and a smooth surface can be obtained. The Se doping level gradually increased, and Se occupied the S position in the lattice as the selenization temperature was increased so that the optical band gap (Eg) of the CNZTSSe film could be adjusted in the range of 1.14 to 1.06 eV. In addition, the Ni doping can inhibit the deep level defect of SnZn and the defect cluster [2CuZn + SnZn]. It reduces the carrier recombination path. Finally, at the optimal selenization temperature of 540 °C, the open circuit voltage (Voc) of the prepared device reached 344 mV and the PCE reached 5.16%.

Interior/Interface Modification of Textured Perovskite for Enhanced Photovoltaic Outputs of Planar Solar Cells by an In Situ Growth Passivation Technology.

To compensate for the photoelectric losses of planar heterojunction perovskite solar cells (PSCs), the development of high-quality textured absorbers with excellent light-harvesting ability and carrier extraction/transfer efficiency is of great significance to achieve a high-efficiency stable photovoltaic output. In this paper, we propose an in situ growth passivation technique to construct high-performance textured absorbers by adding a 2-amino-4-chlorophenol (AC) modifier consisting of multiple groups during the growth of textured perovskite. Initially, according to the Ostwald ripening mechanism, the strongly polar dimethylformamide (DMF) was used as the etchant to systematically study its synergistic effect on the morphology evolution, crystallization kinetics, light-trapping capability, and photovoltaic loss of textured absorbers. An appropriate amount of DMF induces formamidinium cations (FA+) to replace methylammonium cations (MA+) in the perovskite lattice while etching the absorber to form a texture configuration, which effectively broadens the spectral absorption range, thus greatly improving the light-trapping capacity and short-circuit current density of planar PSCs. In contrast, excess DMF deteriorates the device performance due to the excessive corrosion of the perovskite. Moreover, the introduction of the AC modifier is of great significance for passivating deep-level defects and accelerating the charge extraction/transfer. Owing to the electron-donating nature of the Lewis base, the hydroxyl groups with a higher electron density in AC molecules can better coordinate with Pb2+ ion defects, which effectively improves the crystallinity of the textured perovskite, thus suppressing the nonradiative recombination and ultimately improving the photovoltaic outputs of modified devices, particularly the fill factor and the open-circuit voltage. Thus, the photovoltaic performance of the AC-modified planar PSC is significantly better than that of the conventional textured device, with a reverse efficiency of 21.18% and forward efficiency of 20.77%. Owing to the synergistic effect of (1) the superior optical properties of the textured perovskite induced by DMF and (2) excellent charge dynamics driven by AC, the functionalized devices without encapsulation also exhibited good photovoltaic output stability and reproducibility. This work provides novel insights into the growth mechanism of textured absorbers and paves the way for more efficient and stable planar PSCs.

Diluted-CdS Quantum Dot-Assisted SnO2 Electron Transport Layer with Excellent Conductivity and Suitable Band Alignment for High-Performance Planar Perovskite Solar Cells.

An electron transport layer (ETL) with excellent conductivity and suitable band alignment plays a key role in accelerating charge extraction and transfer for achieving highly efficient planar perovskite solar cells (PSCs). Herein, a novel diluted-cadmium sulfide quantum dot (CdS QD)-assisted SnO2 ETL has been developed with a low-temperature fabrication process. The slight addition of CdS QDs first enhances the crystallinity and flatness of SnO2 ETLs so that it provides a promising workstation to obtain high-quality perovskite absorption layers. It also amazingly increases the conductivity of the SnO2 ETL by an order of magnitude and regulates the energy level matching between the SnO2 ETL and perovskite. These outstanding properties greatly accelerate the charge extraction and transfer. Thus, the MAPbI3-based PSCs with such a diluted-CdSQD-assisted SnO2 ETL achieve a maximum power conversion efficiency of 20.78% and obtain a better stability of devices in air. These findings testify the importance and potential of semiconductor QD modification on ETLs, which may pave the way for developing such composite ETLs for further enhancing photovoltaic performance of planar PSCs.

Preferred Film Orientation to Achieve Stable and Efficient Sn-Pb Binary Perovskite Solar Cells.

The preferred orientation of crystalline films in hybrid perovskite materials is known to influence the performance of perovskite solar cells (PSCs). Although the preferred growth along the (112) directions has been reported to promote charge transport within the Pb-based polycrystalline perovskite films, the preferred orientation growth of this facet is still difficult to be achieved due to the higher formation energy compared with the (110) plane. Herein, Sn-Pb binary perovskite films with a well-controlled orientation along the (224) plane were achieved by introducing a simple ultrasonic treatment (UST) into the additive engineering fabricated method. UST is used to process the perovskite precursor solutions of tartaric acid (TA) modified Sn-Pb binary polycrystalline perovskite films to regulate the interactions between PbI2/SnI2 and TA in the intermediate phases. Meanwhile, TA-modulated MA0.9Cs0.1Pb0.75Sn0.25I3-based perovskite films with a preferred orientation of (224) crystal plane were obtained by precisely controlling the UST time to 15 min. The highest power conversion efficiency (PCE) of 15.59% with less hysteresis and improved stability was achieved, while realizing 8.64 and 25.32% enhancements of PCE compared with that of TA-based and control counterparts with (110) preferred orientation, respectively. Our work provides a promising route to obtain preferred orientation growth of polycrystalline perovskite films. In particular, we have shown that this approach improves the performance of Sn-Pb binary PSCs, while such methodology is quite flexible and could also be applied to other low-/non-toxic PSCs.

Hot-Carrier Injection Antennas with Hemispherical AgOx@Ag Architecture for Boosting the Efficiency of Perovskite Solar Cells.

In the past few years, the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased from 3.81 to 25.2%, surpassing those of all almost all thin films solar cells. For high-performance PSCs, it is pivotal to finely regulate the charge dynamics and light management between perovskite and charge-transfer materials to balance the trade-off between optical and electrical properties. In this study, a hemispherical core-shell silver oxide (AgOx) @ silver nanoparticles (Ag NPs) were grown onto the surface of the mesoporous titanium dioxide (m-TiO2) electron-transport layer (ETL) to improve the photogenerated charge transfer without sacrificing the stability of the devices. The results show that the electrical properties of m-TiO2 have been enhanced owing to the injection of a hot carrier in Ag NPs into the m-TiO2 ETL filling the trap states of m-TiO2. However, AgOx on the Ag NP surfaces can isolate the touch between Ag NPs and perovskite, thereby prohibiting the perovskite decomposition. Compared with the control device, the PCE was increased from 17.87 to 20.33% for the device with HOAPs. In the meantime, the long-term stability of the PSCs is not sacrificed, which is pivotal for fabricating PSCs and optoelectronic devices.

Enhancing the Performance of Aqueous Solution-Processed Cu2ZnSn(S,Se)4 Photovoltaic Materials by Mn2+ Substitution.

In this work, the Cu2MnxZn1-xSn(S,Se)4 (0 ≤ x ≤ 1) (CMZTSSe) alloy films were fabricated by a sol-gel method. Meanwhile, the effects of Mn substitution on the structural, morphological, electrical, optical, and device performance were studied systematically. The clear phase transformation from Cu2ZnSn(S,Se)4 (CZTSSe) with kesterite structure to Cu2MnSn(S,Se)4 (CMTSSe) with stannite structure was observed as x = 0.4. The scanning electron microscope (SEM) results show that the Mn can facilitate the grain growth of CMZTSSe alloy films. Since the x was 0.1, the uniform, compact, and smooth film was obtained. The results show that the band gap of the CMZTSSe film with a kesterite structure was incessantly increased in a scope of 1.024-1.054 eV with the increase of x from 0 to 0.3, and the band gap of the CMZTSSe film with stannite structure was incessantly decreased in a scope of 1.047-1.013 eV with the increase of x from 0.4 to 1. Meanwhile, compared to the power conversion efficiency (PCE) of pure CZTSSe device, the PCE of CMZTSSe (x = 0.1) device is improved from 3.61% to 4.90%, and about a maximum enhanced the open-circuit voltage (VOC) of 30 mV is achieved. The improvement is concerned with the enhancement of the grain size and decrease of the Cu instead of Zn (CuZn) anti-site defects. Therefore, it is believed that the adjunction of a small amount of Mn may be an appropriate approach to improve the PCE of CZTSSe solar cells.

Substitution of Ag for Cu in Cu2ZnSn(S,Se)4: Toward Wide Band Gap Absorbers with Low Antisite Defects for Thin Film Solar Cells.

Cation substitution is a promising approach to reduce the antisite defects and further improve the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) cells. In this paper, silver (Ag) has been introduced into Cu2ZnSn(S,Se)4 (CZTSSe) thin film to replace Cu partially and form (Cu1-xAgx)2ZnSn(S,Se)4 (0 ≤ x ≤ 1) (CAZTSSe) alloy films by combination of solution method and a rapid annealing technique. The fundamental properties of the mixed Ag-Cu kesterite compound are systematically reported as a function of the Ag/(Ag+Cu) ratio. The results show that band gap of kesterite CAZTSSe is incessantly increased by adjusting the Ag doping content, indicating that the CAZTSSe alloy film is a potentially applicable bandgap grading absorption layers material to obtain higher CZTSSe device. Furthermore, CAZTSSe alloy films with better electrical performance were also obtained by adjusting the Ag content during film fabrication. Finally, we also observed an increment in open circuit voltage (Voc) by 160 mV and an accompanying rise in device efficiency from 4.24 to 5.95%. The improvement is correlated to the improved grain size and decreased antisite defects of Cu instead of Zn site (CuZn) in the lattice. The Voc enhancement evidences that the solution method is facile and viable to achieve proper cation substitution toward higher efficiency kesterite solar cells. In addition, the CAZTSSe cell also displays better charge collection performance because of the higher fill factor (FF) and power conversion efficiency (PCE). Therefore, it can be concluded that the doping of Ag is a potentially appropriate method to reduce the Cuzn antisite defects of CZTSSe and improve efficiency of CZTSSe device.

Investigation on the Selenization Treatment of Kesterite Cu2Mg0.2Zn0.8Sn(S,Se)4 Films for Solar Cell.

High-selenium Cu2Mg0.2Zn0.8Sn(S,Se)4 (CMZTSSe) films were prepared on a soda lime glass substrate using the sol-gel spin coating method, followed by selenization treatment. In this work, we investigated the effects of selenization temperature and selenization time on the crystal quality, and electrical and optical properties of CMZTSSe films. The study on the micro-structure by XRD, Raman, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS) analysis showed that all CMZTSSe samples had kesterite crystalline structure. In addition, the crystalline quality of CMZTSSe is improved and larger Se takes the site of S in CMZTSSe with the increase of selenization temperature and selenization time. When increasing the selenization temperature from 500 to 530 °C and increasing the annealing time from 10 to 15 min, the morphological studies showed that the microstructures of the films were dense and void-free. When further increasing the temperature and time, the crystalline quality of the films began to deteriorate. In addition, the bandgaps of CMZTSSe are tuned from 1.06 to 0.93 eV through adjusting the selenization conditions. When CMZTSSe samples are annealed at 530 °C for 15 min under Se atmosphere, the crystal quality and optical-electrical characteristics of CMZTSSe will be optimal, and the grain size and carrier concentration reach maximums of 1.5-2.5 µm and 6.47 × 1018 cm-3.

Investigation of Optimum Mg Doping Content and Annealing Parameters of Cu2MgxZn1-xSnS4 Thin Films for Solar Cells.

Cu2MgxZn1-xSnS4 (0 ≤ x ≤0.6) thin films were prepared by a simple, low-temperature (300 °C) and low-cost sol-gel spin coating method followed by post-annealing at optimum conditions. We optimized the annealing conditions and investigated the effect of Mg content on the crystalline quality, electrical and optical performances of the Cu2MgxZn1-xSnS4 thin films. It was found that the Cu2MgxZn1-xSnS4 film annealed at 580 °C for 60 min contained large grain, less grain boundaries and high carrier concentration. Pure phase kesterite Cu2MgxZn1-xSnS4 (0 ≤ x ≤ 0.6) thin films were obtained by using optimal annealing conditions; notably, the smaller Zn2+ ions in the Cu2ZnSnS4 lattice were replaced by larger Mg2+ ions. With an increase in x from 0 to 0.6, the band gap energy of the films decreased from 1.43 to 1.29 eV. When the ratio of Mg/Mg + Zn is 0.2 (x = 0.2), the grain size of Cu2MgxZn1-xSnS4 reaches a maximum value of 1.5 µm and the surface morphology is smooth and dense. Simultaneously, the electrical performance of Cu2MgxZn1-xSnS4 thin film is optimized at x = 0.2, the carrier concentration reaches a maximum value of 3.29 × 1018 cm-3.

Activating Old Materials with New Architecture: Boosting Performance of Perovskite Solar Cells with H2O-Assisted Hierarchical Electron Transporting Layers.

The breakthrough of organometal halide perovskite solar cells (PSCs) based on mesostructured composites is regarded as a viable member of next generation photovoltaics. In high efficiency PSCs, it is crucial to finely optimize the charge dynamics and optical properties matching between the perovskites and electron transporting materials to relax the trade-off between the optical and electrical requirements. Here, a simple antipolar route with H2O as the additive is proposed to prepare hierarchical electron transporting layers to boost the efficiency of dopant-free PSCs. The photovoltaic performance of the PSCs is enhanced owing to increased light-scattering, improved Ostwald ripening, and photo-generated electron extraction. Optimization of the H2O addition enables a valid power conversion efficiency of 19.9% (reverse scan: 20.02%) to be achieved. The device can retain more than 90% of its initial performance after storage in air more than 30 days. These results are inspiring in that they present that a mesoporous transporting layer could be easily re-constructed to hierarchical architecture by the antipolar method to further improve the performance of PSCs.

Novel Insight into the Role of Chlorobenzene Antisolvent Engineering for Highly Efficient Perovskite Solar Cells: Gradient Diluted Chlorine Doping.

Chlorobenzene and diethyl ether were chosen as an antisolvent to control the crystallization of CH3NH3PbI3. Under the condition of similar crystallization for both perovskite films, the obvious larger short-circuit current density for CH3NH3PbI3 film treated by chlorobenzene prompted us to unveil the roles of chlorobenzene in the perovskite films via adjusting the dropping amount of chlorobenzene. A novel insight of chlorobenzene function was revealed, that is, gradient diluted chlorine doping in the CH3NH3PbI3 film, which forms a gradient band gap in the perovskite films, prompts photogenerated carriers accumulating at the interface, makes the electron transport faster, and effectively enhances the power conversion efficiency (PCE) of solar cells. The maximum PCE of 20.58% has been achieved under standard AM1.5 conditions. Moreover, this technique exhibits very high reproducibility, and 20 devices fabricated in one batch can yield an average PCE of 20.31%.

Dual-Stimulus-Triggered Programmable Drug Release and Luminescent Ratiometric pH Sensing from Chemically Stable Biocompatible Zinc Metal-Organic Framework.

Metal-organic frameworks (MOFs), as drug delivery carriers, with high loading capacity and controllable release behavior can provide a more efficacious therapy in cancer treatments. In our work, a novel biocompatible zinc MOF Zn-cpon-1 with the (3,6)-connected rtl 3D topological network was designed and synthesized via employing ClO4- anion as template. The optically and chemically stable Zn-cpon-1 could be verified as a pH-responsive dual-emission platform and excellent drug delivery carrier with higher 5-fluorouracil (5-FU) (44.75 wt %) loading behavior than 6-mercaptopurine (6-MP) (4.79 wt %) ascribed to the influence of size and shape matching. The multiple interactions between Zn-cpon-1 and 5-FU drug molecules have been discussed and evidenced, which could be quantitatively estimated via the rate constant related to the topological structure. Specially, the gust release behavior of 5-FU@Zn-cpon-1 microcrystal was described and programmed via the Weibull distribution model and could be dual-triggered by the temperature and pH stimulus. This study illustrates that the Zn-cpon-1 without any postmodification performs a favorable potential of being used as biomedical drug delivery alternative carriers in effective drug payload, flexible release administration, and superior dual-stimuli responsiveness.

Synthesis of simple, low cost and benign sol-gel Cu2In x Zn1-x SnS4 alloy thin films: influence of different rapid thermal annealing conditions and their photovoltaic solar cells.

Cu2In x Zn1-x SnS4 (x = 0.4) alloy thin films were synthesized on soda lime glass (SLG) substrate by a simple low-cost sol-gel method followed by a rapid annealing technique. The influence of sulfurization temperature and sulfurization time on the structure, morphology, optical and electrical properties of Cu2In x Zn1-x SnS4 thin films was investigated in detail. The XRD and Raman results indicated that the crystalline quality of the Cu2In x Zn1-x SnS4 alloy thin films was improved, accompanied by metal deficiency, particularly tin loss with increasing the sulfurization temperature and sulfurization time. From absorption spectra it is found that the band gaps of all Cu2In x Zn1-x SnS4 films are smaller than that (1.5 eV) of the pure CZTS film due to In doping, and the band gap of the Cu2In x Zn1-x SnS4 films can be tuned in the range of 1.38 to 1.19 eV by adjusting the sulfurization temperature and sulfurization time. Hall measurement results showed that all Cu2In x Zn1-x SnS4 alloy thin films showed p-type conductivity characteristics, the hole concentration decreased and the mobility increased with the increase of sulfurization temperature and sulfurization time, which is attributed to the improvement of the crystalline quality and the reduction of grain boundaries. Finally, the Cu2In x Zn1-x SnS4 film possessing the best p-type conductivity with a hole concentration of 9.06 × 1016 cm-3 and a mobility of 3.35 cm2 V-1 s-1 was obtained at optimized sulfurization condition of 580 °C for 60 min. The solar cell using Cu2In x Zn1-x SnS4 as the absorber obtained at the optimized sulfurization conditions of 580 °C for 60 min demonstrates a power conversion efficiency of 2.89%. We observed an increment in open circuit voltage by 90 mV. This work shows the promising role of In in overcoming the low V oc issue in Cu-kesterite thin film solar cells.

Role of hydrogen plasma pretreatment in improving passivation of the silicon surface for solar cells applications.

We have investigated the role of hydrogen plasma pretreatment in promoting silicon surface passivation, in particular examining its effects on modifying the microstructure of the subsequently deposited thin hydrogenated amorphous silicon (a-Si:H) passivation film. We demonstrate that pretreating the silicon surface with hydrogen plasma for 40 s improves the homogeneity and compactness of the a-Si:H film by enhancing precursor diffusion and thus increasing the minority carrier lifetime (τ(eff)). However, excessive pretreatment also increases the density of dangling bond defects on the surface due to etching effects of the hydrogen plasma. By varying the duration of hydrogen plasma pretreatment in fabricating silicon heterojunction solar cells based on textured substrates, we also demonstrate that, although the performance of the solar cells shows a similar tendency to that of the τ(eff) on polished wafers, the optimal duration is prolonged owing to the differences in the surface morphology of the substrates. These results suggest that the hydrogen plasma condition must be carefully regulated to achieve the optimal level of surface atomic hydrogen coverage and avoid the generation of defects on the silicon wafer.