Search

The potential-induced degradation (PID) of p-type crystalline silicon passivated emitter and rear cell (PERC) is a critical issue causing severe output power loss. In this paper, a gradient-designed capping layer consisting of silicon nitride/silicon oxynitride/silicon oxide (SiNx/SiNxOy/SiOx) is proposed as the surface coating for p-type PERC solar cells. The capping layer improves the short wavelength spectral response due to its better anti-reflection effect. An impressive efficiency of 23.52% has been achieved on mass production line. A long-term PID evolution up to 672 h is performed for glass/back sheet PERC cell modules under stringent conditions with the ambient temperature of 85 °C, relative humidity of 85%, and the applied voltage of 1500 V. The current–voltage (light I-V, dark I-V) parameters of the modules were measured, as well as the electroluminescence, to evaluate the effect of sodium ion migration in PERC solar cells. It is shown that monofacial PERC solar modules suffer from shunt of PN junction under PID stress, which can be obviously suppressed by gradient-designed capping layers. The optimized PERC solar modules show excellent PID resistance, showing great potential for lower levelized cost of energy (LCOE) of photovoltaic power generation.

According to IAEA regulations, the spent nuclear fuel transportation cask must be able to withstand a free drop from the height of 9 meters on an unyielding surface. The impact limiter of the cask absorbs most of the impact energy and reduces the deceleration loads on the cask and contents. In order to accurately estimate the safety of the cask and the spent nuclear fuel, the calculation of drop acceleration is very important. In this study, based on the absorption of energy by an impact limiter is equal to the work done in crushing a volume, the maximum deceleration is estimated during collision process between cask and the ground. Then using the LS-DYNA computer program to simulate the cask drop behavior of 9 meters free drop. By comparing the results of theoretical analysis, numerical simulation and actual drop tests, the cask maximum acceleration and the impact limiter deformation are in good agreement, which prove the validity of the spent nuclear fuel transportation cask drop analysis. The stress intensity results for 9 meters free drop loading cases satisfy the allowable stress limit criteria as presented in “ASME Boiler and Pressure Vessel Code”. The spent nuclear fuel transportation cask meets the requirements of IAEA in the 9m free drop hypothetical accident conditions.

By using the way of real analysis and the weight functions, a few equivalent statements of a Hilbert-type integral inequality in the whole plane with the internal variables and the best possible constant factor related to the Riemann-zeta function is proved. The operator expression and some particular cases are considered.

Experimental evidence suggests that exposure to cadmium (Cd) could affect immune cells in vivo and in vitro. However, the associations of long-term Cd exposure with white blood cell (WBC) subtype counts and hemogram-derived indices have been rarely investigated. Therefore, we evaluated these relationships in residents of cadmium-polluted areas.This cross-sectional study included 431 participants aged 45-75 years without occupational exposure histories from Cd-contaminated areas of southern China. We detected WBC, neutrophil, lymphocyte, and monocyte counts using routine blood tests and calculated neutrophil-lymphocyte ratio (NLR), systemic inflammation response index (SIRI), and lymphocyte-monocyte ratio (LMR). Urinary Cd (U-Cd) was measured with inductively coupled plasma mass spectrometry and adjusted for creatinine. To evaluate the associations of U-Cd with peripheral WBC subtype counts and indices, we performed multivariate linear regression, logistic regression and subgroup analyses using U-Cd categorized into quartiles.In models adjusted for all potential confounders, U-Cd was negatively associated with WBC, neutrophil, and monocyte counts in Q2, compared with Q1 of U-Cd (p 0.05). A similar relationship was observed between U-Cd and NLR and SIRI, whereas the corresponding association for LMR was positive (p 0.05). In subgroup analyses, U-Cd was negatively associated with neutrophil count, except for never smokers, after full adjustment.U-Cd was negatively associated with WBC count, neutrophil count, monocyte count, NLR, and SIRI, and positively associated with LMR. Therefore, neutrophil count could be a potential indicator of long-term Cd exposure-associated immunosuppressive effect.

Purpose: To investigate the therapeutic effect of dexamethasone on rabbits suffering from oral ulcers, and the underlying mechanism(s) of action. Methods: A rabbit model of oral ulcer was established by applying 40 % glacial acetic acid solution to the oral buccal membranes of the animals. Three groups of rabbits were used. Changes in area of the oral ulcer were recorded after dexamethasone administration. Levels of epidermal growth factor (EGF) were assayed using reverse transcription PCR (RT-PCR), while MDA levels and expression levels of IL- 6, IL-8 and TNF-α were determined by enzyme-linked immunosorbent assay (ELISA). Local histopathological changes were examined histologically with the aid of hematoxylin and eosin (H & E) staining. Results: There were reductions in ulcer areas in group C on the 2nd, 4th and 7th days of dexamethasone administration, when compared with group B (p < 0.05). The EGF levels in the buccal mucosa of rabbits in groups B and C were significantly higher than those in group A (p < 0.05), while the highest EGF level was in group C (p < 0.05). The levels of MDA, IL-6, IL-8, and TNF-α significantly increased in groups B and C (p < 0.05). Results from H & E staining showed lower levels of inflammatory cells in group C than in group B, with visible proliferation of fibroblast cells and epithelial cells in group C after dexamethasone administration. Conclusion: Dexamethasone accelerates healing of oral ulcer by regulating EGF levels. This finding provides a new approach to the treatment of oral ulcers.

Cadmium accumulates in the kidney and causes inflammation. The NLRP3 inflammasome has been linked to the pathogenesis of inflammation. Hyperoside (HYP) possesses potent nephroprotective properties against of kidney injury. This study aimed to research the effects and related mechanism of HYP on Cd-induced kidney damage. Wide-type and NLRP3

Purpose The purpose of this study was to investigate the reproducibility of fluid-phase measurements in PBS-treated sputum supernatant, processed using the two-step method, of healthy and stable COPD individuals. Methods Nine healthy subjects and 23 stable COPD patients provided sputum twice within 6 days. A two-step sputum processing method was used to obtain PBS-treated supernatant and sputum cells. Soluble protein markers and IgG and IgM autoantibody profiles in PBS supernatant were analyzed using customized microarrays. Repeatability of measurements was assessed by paired-sample testing and an intraclass correlation coefficient, then graphically reported by Bland-Altman plot. Results There was no significant difference between the repeated detection of 8/10 types of soluble protein markers, all 13 types of IgG autoantibodies, and 12/13 types of corresponding IgM autoantibodies in PBS supernatant. The repeatability of measurements in PBS supernatant was substantial to very good for interleukin 6 (IL6), IL8, IL13, IL10, IL33, vascular endothelial growth factor, soluble receptor for advanced glycation end-products, and tumor necrosis factor-α; for IgG autoantibodies against aggrecan, centromere protein B (CENP-B), collagen II, collagen IV, cytochrome C, elastin, heat shock protein 47 (HSP47), HSP70, and La/Sjogren syndrome type B antigen; for IgM autoantibodies against CENP-B, collagen I, collagen II, collagen IV, cytokeratin 18, and HSP70; and for sputum neutrophils, macrophages and eosinophils count. Bland-Altman plots suggested good consistency within repeated measurements. Stable COPD patients differed from healthy subjects in the proportion of neutrophils and eosinophils; relative fluorescence intensity of anti-cytochrome C IgG, anti-aggrecan IgM, and anti-cytochrome C IgM. There was a significant positive correlation for stable COPD patients between sputum anti-collagen II IgG and post-bronchodilator FEV1%. Conclusion We confirmed fluid-phase measurements in PBS-treated sputum supernatant by high-throughput techniques with good repeatability. We demonstrated the presence of IgG and IgM autoantibodies to multiple antigens in the airways of COPD patients.

SummaryHuman limb skeletal system consists of both bone and cartilage which originated from fetal cartilage. However, the roadmap of chondrocyte divergent differentiation to bone and articular cartilage has yet to be established. Epiphysis possesses articular cartilage, growth plate and the secondary ossification center (SOC), making it an ideal model to uncover the trajectory of chondrocyte divergent differentiation. Here, we mapped differentiation trajectory of human chondrocyte during postnatal finger epiphysis development by using single-cell RNA sequencing. Our results uncovered that chondroprogenitors have two differentiation pathways to hypertrophic chondrocytes during ossification, and one pathway to articular chondrocytes for formation of cartilages. Interestingly, we found that, as an addition to the known typical endochondral ossification path from resting, proliferative to hypertrophic chondrocytes, there was a bypass by which chondroprogenitors differentiate into hypertrophic chondrocytes without proliferative stage. Furthermore, our results revealed two new chondrocyte subpopulations (bypass chondrocytes as it appeared in the ossification bypass, and ID1+ chondroblasts in articular chondrocyte path) during postnatal epiphysis development in addition to six well-known subpopulations. Overall, our study provides a comprehensive roadmap of chondrocyte differentiation in human epiphysis thereby expanding the knowledge of bone and articular cartilage, which could be utilized to design biotherapeutics for bone and articular cartilage regeneration.

Aldo-keto reductases (AKRs) mediated stereoselective reduction of prochiral carbonyl compounds is an efficient way of preparing single enantiomers of chiral alcohols due to their high chemo-, enantio-, and regio-selectivity. To date, the application of AKRs in the asymmetric synthesis of chiral alcohols has been limited, due to the challenges of cloning and purifying. In this work, the aldo-keto reductase (AKR3-2-9) from Bacillus sp. was obtained, purified and proved to be NADPH-dependent. It exhibits good bioactivity and stability at 37 &deg, C, pH 6.0. AKR3-2-9 is catalytically active on 11 pairs of substrates such as 3-methylcyclohexanone and methyl pyruvate, among which it showed the highest catalytic activity for acetylacetone. In addition, AKR3-2-9 was able to be resistant to five common organic solvents such as methanol and ethanol, it retained high catalytic activity even in a reaction system containing 10% v/v organic solvent for 6 h, which indicates its broad substrate spectrum and exceptional organic solvent tolerance. Furthermore, its three-dimensional structure was constructed and catalytic-site-analysis of the enzyme was conducted. Notably, it was capable of catalyzing the reaction of the key intermediates of duloxetine. The extensive substrate spectrum and predominant organic solvents resistance makes AK3-2-9 a promising enzyme which can be potentially applied in medicine synthesis.

OBJECTIVE: To survey the residents for their understanding of Coronavirus Disease 2019 (COVID-19)-related knowledge, attitude and practices (KAP) in two hard hit provinces of China to facilitate the governmental decisions on strategies against the disease. METHODS: We invited the participants from Hubei and Henan Provinces of China for an internetbased survey starting from 12:00 on February 21, 2020 to 12:00 on February 23. The survey included the general conditions, KAP of COVID-19, psychological status and living conditions of the residents. RESULTS: The effective response rate of the questionnaire was 98.9%. The mean (P25, P75) age of the participants was 19 (16, 40) years, and 54.3% of them were students. Social media were the most important source of information concerning the pandemic of the respondents. The respondents had a high awareness of person-to-person transmission of the virus through the respiratory tract or droplets but showed a relatively low level of awareness of the population susceptible to COVID-19 and its specific symptoms. The results of multivariate analysis showed that women, undergraduate students (including college students) and higher degree holders had better knowledge of COVID-19 (P < 0.05); the proportion of respondents who expressed to have different levels of psychological stressed such as worry, anxiety and panic reached 77.2%; 16.7% of the responders considered psychological interventions necessary for their psychological conditions; 63.6% of the respondents confessed a bias against the people returning from Hubei and Henan provinces, while 22.4% worried that they might be biased because of their residence in Hubei and Henan. The rate of personal protective equipment shortage was as high as 69.4%; the rates of the responders who would "covering the mouth and nose when coughing or sneezing", "properly use masks in accordance with regulations", "maintain proper hand hygiene ", "avoid gatherings with relatives and friends" and "refrain from going to public places" were 92.4%, 95.9%, 93.5%, 88.8% and 93.1%, respectively. Women and groups with good knowledge of the disease reported better protective behaviors against the diseases (P < 0.05). CONCLUSIONS: The residents in Hubei and Henan Provinces have generally good KAP related to COVID-19, and the online platforms plays a positive role to in circulating epidemic-related information. It is essential to further increase the supply of the protective materials and pay more attention to the mental health of the residents during the pandemic, and psychological counseling and psychological protection should be provided if necessary.

The dopant-free back contact solar cells are demonstrated based on hole selective contact material, chromium trioxide (CrO x , x x is first applied in silicon based solar cell as the emitter. Integrating 5 nm CrO x and 2 nm LiF x into solar cell as the emitter and the back surface filed, resulted in a device efficiency of 13.6%. For further improvement, the back contact solar cell reaching an efficiency of 15.8% was fabricated, by implementing the multilayer films of CrO x (5 nm)/Au (4 nm)/ CrO x (5 nm) as the emitter. The formation of Cr(OH) 3 in ambient condition, resulted in a lower work function (4.8 eV) of the CrO x film. Furthermore, the multilayer back contact solar cell demonstrated a high stability due to CrO x covered with 500 nm Ag, when stored in ambient air longer than 170 days.

Lili Guan,1,* Jiawen Xu,1,* Weiliang Wu,1,* Jianhua Chen,1,* Xiaoying Li,2,* Bingpeng Guo,1 Yuqiong Yang,1 Yating Huo,1 Luqian Zhou,1 Rongchang Chen1 1State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China; 2The First Affiliated Hospital, School of Clinical Medicine of Guangdong Pharmaceutical University, Guangzhou, China *These authors contributed equally to this work Purpose: Patients with advanced-stage COPD often experience severe hypoxemia. Treatment with long-term oxygen therapy (LTOT) may relieve patients’ symptoms and increase survival. As COPD is incurable, improving patients’ health-related quality of life is important. The Chinese version of the Severe Respiratory Insufficiency Questionnaire (SRI) is valid for patients with hypercapnic COPD undergoing noninvasive positive airway pressure ventilation at home. However, the reliability and validity of the Chinese SRI for patients with COPD undergoing LTOT have not been investigated. Patients and methods: We analyzed reliability using Cronbach’s α coefficient. Construct validity was assessed with principal, exploratory, and confirmatory factor analysis. Concurrent validity was evaluated through the correlation between SRI domains and Chronic Respiratory Disease Questionnaire (CRQ) domains. Content validity was assessed by calculating the correlation between each SRI item score and the total score for the relevant domain. Results: In total, 161 patients participated in this study. The Cronbach’s α coefficient for all SRI domains was >0.7, except for the attendant symptoms and sleep domain. Exploratory and confirmatory factor analysis showed a good model fit for each domain, but the factors extracted from each domain were correlated. SRI and CRQ domains correlated well with respect to similar aspects of health-related quality of life, indicating good concurrent validity. Content validity was indirectly shown by a good correlation between each item score and the total score of the relevant domain. Conclusion: The Chinese version of the SRI has a good reliability and validity for patients with COPD undergoing LTOT in China. Keywords: severe respiratory insufficiency questionnaire, long-term oxygen therapy, health-related quality of life, chronic obstructive pulmonary disease

The biosynthesis of chiral alcohols has important value and high attention. Aldo–keto reductases (AKRs) mediated reduction of prochiral carbonyl compounds is an interesting way of synthesizing single enantiomers of chiral alcohols due to the high enantio-, chemo- and regioselectivity of the enzymes. However, relatively little research has been done on characterization and apply of AKRs to asymmetric synthesis of chiral alcohols. In this study, the AKR from Candida tropicalis MYA-3404 (C. tropicalis MYA-3404), was mined and characterized. The AKR shown wider optimum temperature and pH. The AKR exhibited varying degrees of catalytic activity for different substrates, suggesting that the AKR can catalyze a variety of substrates. It is worth mentioning that the AKR could catalytic reduction of keto compounds with benzene rings, such as cetophenone and phenoxyacetone. The AKR exhibited activity on N,N-dimethyl-3-keto-3-(2-thienyl)-1-propanamine (DKTP), a key intermediate for biosynthesis of the antidepressant drug duloxetine. Besides, the AKR still has high activity whether in a reaction system containing 10%-30% V/V organic solvent. What’s more, the AKR showed the strongest stability in six common organic solvents, DMSO, acetonitrile, ethyl acetate, isopropanol, ethanol, and methanol. And, it retains more that 70% enzyme activity after 6 hours, suggesting that the AKR has strong solvent tolerance. Furthermore, the protein sequences of the AKR and its homology were compared, and a 3D model of the AKR docking with coenzyme NADPH were constructed. And the important catalytic and binding sites were identified to explore the binding mechanism of the enzyme and its coenzyme. These properties, predominant organic solvents resistance and extensive substrate spectrum, of the AKR making it has potential applications in the pharmaceutical field.

In 2 O 3 thin films were prepared by reactive evaporation with post-annealing treatment at forming gas of N 2 and H 2 . After post-annealing treatment, the films annealed at forming gas achieved lowest resistivity of 2.70 × 10 −4 Ω cm. The XRD results show that the In 2 O 3 films annealed in forming gas and N 2 with good recrystallization. In the forming gas annealing process, hydrogen plays a key role in the generation of oxygen vacancies and enhances the formation of In–OH bond which may influence the electrical and optical properties of the In 2 O 3 films.

Weiliang Wu,1,* Lili Guan,1,* Xiaoying Li,2,* Lin Lin,1 Bingpeng Guo,1 Yuqiong Yang,1 Zhenyu Liang,1 Fengyan Wang,1 Luqian Zhou,1 Rongchang Chen1 1Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, 2Department of Respiratory Medicine, The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou, China *These authors contributed equally to this work Purpose: To evaluate the compatibility and correlation between noninvasive surface respiratory electromyography and invasive transesophageal diaphragmatic electromyography measurements as facilitating indicators of neural respiratory drive (NRD) evaluation during treadmill exercise.Patients and methods: Transesophageal diaphragmatic electromyogram activity (EMGdi,es) and surface inspiratory electromyogram (EMG) activity, including surface diaphragmatic EMG activity (EMGdi,sur), surface parasternal intercostal muscle EMG activity (EMGpara), and surface sternocleidomastoid EMG activity (EMGsc), were detected simultaneously during increasing exercise capacity in 20 stable patients with COPD. EMGdi,es, EMGdi,sur, EMGpara, and EMGsc were quantified using the root mean square (RMS) and were represented as RMSdi,es, RMSdi,sur, RMSpara, and RMSsc, respectively.Results: There was a significant association between EMGdi,es and EMGdi,sur (r=0.966, p

We conducted a randomised controlled trial to assess the effects of daily breathing pattern changes to stable patients with COPD excluding the confounding factors of inspiratory muscle mobilization, by ensuring the load intensities of two inspiratory training devices were equal.Sixty patients with COPD were randomised to three groups: resistive-IMT group (T-IMT, 21 patients), threshold-IMT (R-IMT, 19 patients), and a control group (20 patients). Inspiratory load intensity for both methods was set at 60% of maximal inspiratory pressure (MIP), a measure of inspiratory muscle strength, which, along with health-related quality of life (HRQoL), degree of dyspnoea, and exercise capacity, were conducted before and after 8 weeks of daily IMT.At 8 weeks, there was no significantly difference of MIP between the R- and T-IMT groups (P 0.05). Chronic Respiratory Disease Questionnaire and Transition Dyspnea Index scores improved significantly after each training program compared with controls (P 0.05), and R-IMT was significant better (P 0.05). R-IMT was better than T-IMT in performance of exercise (P 0.05).In summary, in clinically stable patients with COPD, 8 weeks of R-IMT was superior to 8 weeks of equal-intensity T-IMT in improving HRQoL, degree of dyspnoea, and exercise capacity.

The morphology, optical and composition properties of Zinc sulfide (ZnS) thin films prepared by thermal evaporation method were investigated. The as-deposited ZnS thin films exhibited good smoothness and showed (1 1 1) preferential orientation. The atomic concentrations of Zn = 49.98% and S = 50.02% were calculated from the XPS spectrum. Band-gap of 3.72 eV was deduced from the optical transmittance spectra. The power conversion efficiency (PCE) of the hydrogen doped AZO (HAZO)/ZnS/textured p-Si heterojunction solar cells was η = 8.83%, which is the best so far to our knowledge. The solar cell without encapsulation exhibited no degradation for more than 2400 h, indicating the good stability of the device.

Luqian Zhou,1,* Xiaoying Li,1,* Lili Guan,1,* Jianhua Chen,1 Bingpeng Guo,1 Weiliang Wu,1 Yating Huo,1 Ziqing Zhou,1 Zhenyu Liang,1 Yuqi Zhou,2 Jie Tan,3 Xin Chen,4 Yuanlin Song,5 Rongchang Chen1 1Department of Respiratory Medicine, State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, 2Department of Respiratory Medicine, The Third Affiliated Hospital of Sun-Yat Sen University, 3Department of Respiratory Medicine, The First Affiliated Hospital, School of Clinical Medicine of Guangzhou Pharmaceutical University, 4Department of Respiratory Medicine, Zhujiang Hospital of Southern Medical University, Guangzhou, 5Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, People’s Republic of China *These authors contributed equally to this work Background: The benefits of noninvasive positive pressure ventilation (NPPV) in patients with hypercapnic COPD are controversial. It is presumed that methodology and appropriate use of NIV ventilator might be crucial for the outcomes. With the new built-in software, the performance of NIV can be monitored at home, which can guarantee the compliance and appropriate use. This study investigated effects of home use of NIV in hypercapnia in COPD patients using the NIV ventilator with built-in software for monitoring. Methods: The current multicenter prospective, randomized, controlled trial enrolled patients with stable GOLD stages III and IV hypercapnic COPD. Patients were randomly assigned via a computer-generated randomization sequence, with a block size of four patients, to continue optimized treatment (control group) or to receive additional NPPV (intervention group) for 3months. The primary outcome was arterial carbon dioxide pressure (PaCO2). Data were derived from built-in software and analyzed every 4weeks. Analysis was carried out with the intention to treat. This study is registered with ClinicalTrials.gov, number NCT02499718. Results: Patients were recruited from 20 respiratory units in China from October 1, 2015, and recruitment was terminated with a record of the vital statistics on May 31, 2016. A total of 115 patients were randomly assigned to the NPPV group (n=57) or the control group (n=58). Patients complied well with NPPV therapy (mean [± standard deviation] day use 5.6±1.4h). The mean estimation of leaks was 37.99±13.71L/min. The changes in PaCO2 (-10.41±0.97 vs -4.32±0.68mmHg, P=0.03) and 6-min walk distance (6MWD) (38.2% vs 18.2%,P=0.02) were statistically significant in the NPPV group versus the control group. COPD assessment test (CAT) showed a positive trend (P=0.06) in favor of the NPPV group. Pulmonary function and dyspnea were not different between groups. Conclusion: Ventilators equipped with built-in software provided methodology for monitoring NIV use at home, which could facilitate the improvement of compliance and quality control of NIV use. It was shown that three months use of NIV at home could reduce the PaCO2 and improve exercise tolerance (6MWD) in chronic hypercapnic COPD patients. Keywords: COPD, noninvasive positive pressure ventilation, long-term oxygen therapy, chronic respiratory failure, built-in software

In this study, we present novel multilayer back contact (MLBC) solar cells employing V2Ox (8 nm)/metal/V2Ox (8 nm) (VMV) multilayers as dopant-free hole-selective contacts deposited using a thermal evaporation process at low temperature. The optimized V2Ox films have a high work function and reduced O-deficiency in-gap state energy owing to the introduction of a carefully controlled O2 partial pressure during the evaporation process. The contact resistivities of VMV (12 nm Ag) and VMV (4 nm Au) contacts with n-Si are 1.58 mΩ cm2 and 0.04 mΩ cm2, respectively, which are less than that of a 16 nm V2Ox/n-Si contact. Interestingly, VMV (Au)/n-Si MLBC solar cells demonstrate improved charge carrier transport, leading to an induced p–n junction. Moreover, the dominant interfacial charge carrier transport properties of MLBC solar cells with VMV (Ag)/n-Si and VMV (Au)/n-Si contacts correspond with the diffusion–recombination model, whereas, those of MLBC solar cells with V2Ox/n-Si and VMV (Ca)/n-Si contacts correspond with the multi-tunneling capture emission model at a high-forward-bias voltage. The use of VMV (4 nm Au) as an emitter achieves an efficiency of 19.02% for this type of MLBC solar cell, which is greater than that of V2Ox/n-Si solar cells (17.58%). This work has important implications for enabling the fabrication of low-performance dopant-free back contact solar cells with high stability using a simple fabrication process.