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The SnZn defect passivation and heterojunction interface energetics‐modification are crucial for further improvement of open‐circuit voltage (Voc) and efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Herein, a simple but effective cation substitution strategy is reported to promote the performance of CZTSSe devices by simultaneously modifying the absorber and heterojunction interface. This is achieved by introducing the organic silicon salt C8H20O4Si into CZTSSe precursor solution as a source of silicon to partially substitute Sn with Si. Systematic studies reveal that there are two mechanisms synergistically contributing to the increase of efficiency: 1) This strategy can passivate the undesired SnZn defect in CZTSSe absorber more efficiently, leading to at least one order of magnitude lower SnZn defect density and beneficial carrier transport properties; 2) After Si incorporation, the conduction band minimum of the CZTSSe is upshifted, thus enlarging the bandgap, which ultimately optimizes the energy level structure at the CdS/CZTSSe interface and reduces interfacial energy loss by decreasing the carrier transport barrier. Consequently, the CZTSSe device with 7% Si substitution delivers a satisfactory efficiency of 13.02% owing to an increase in Voc. It is hoped the Si substitution strategy reported here can provide inspiration for developing advanced CZTSSe devices with broad application prospects. [ABSTRACT FROM AUTHOR]

Abundant intrinsic defects and defect clusters in Cu2ZnSn(S,Se)4 (CZTSSe) solar cells lead to severe nonradiative recombination and limited photoelectric performance. Therefore, developing effective method to suppress the detrimental defects is the key to achieve high‐efficiency solar cell. Herein, a convenient two‐step cooling strategy in selenization process is reported to suppress the CuZn and SnZn defects and defect clusters synergistically. The results show that rapid cooling during section from selenization temperature to turning temperature can inhibit the volatilization of Sn and restrain the corresponding Sn‐related defects, while slow cooling during the subsequent temperature section can reduce the degree of Cu‐Zn disorder. Benefitting from the synergistic effect of two‐step cooling, a significantly lowered concentration of SnZn and CuZn defect and their defect clusters [2CuZn+SnZn] in absorber is observed, meanwhile, a reduced band tailing effect and promoted carrier collection efficiency of the photovoltaic device is obtained. Finally, a device with improved open‐circuit voltage (Voc) of 505.5 mV and efficiency of 12.87% is achieved. This study demonstrates the impact of cooling process on defects controlling for the first time and provides a simple and effective new strategy for intrinsic defect control, which may be universal in other inorganic thin film solar cells. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of the environmentally friendly Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is lower than its predecessor Cu(In,Ga)Se2 solar cells. Severe carrier recombination at the CZTSSe/CdS interface is one major reason that results in a large open‐circuit voltage loss. Doping zinc into CdS is a feasible strategy to modifying the CdS buffer layer film, but the present methods are not satisfactory. In this study, novel zinc incorporation strategy is developed to deposit a gradient composition ternary ZnxCd1–xS buffer layer for optimizing the heterojunction interface. The application of gradient composition ZnxCd1–xS buffer layer constructs a gradient conduction band energy configuration in the CZTSSe/buffer layer interface, which highly reduces the interface recombination. The suppressed interface recombination contributes to the enhanced open circuit voltage and device performance. Consequently, the CZTSSe solar cell based on gradient composition ZnxCd1–xS buffer layers achieves champion efficiency of 12.35% with VOC of 504.81 mV, JSC of 36.90 mA cm−2, and FF of 66.28%. It is worth noting that flammable and the toxic hydrazine solvent are replaced by the safe and low‐toxic 2‐methoxyethanol, making it more promising for the future commercialization of CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

Solution processing of Cu(In,Ga)Se2 (CIGS) absorber makes it cost‐competitive in the photovoltaic market. It is reported that copper‐poor ordered vacancy compound (OVC) is crucial for high performance CIGS solar cells. However, in solution process method, controllable formation of OVC is unavailable and limited research has been carried out. In this work, the controllable formation of the OVC phase on the CIGS surface is successful by controlling the selenization temperature and intentional variation of Cu/(In+Ga) stoichiometry in precursors for top layers and bulk layers deposition. The effects of OVC contents on the device performance are investigated. The CIGS thin film with OVC phase exhibits a lower valence band position. Meanwhile, the CIGS devices with optimized OVC content show decreased interface defects density and better carrier collection ability. The above advantages translate into a champion PCE of 16.39% for CIGS device with OVC phase, which is the champion performance among non‐hydrazine solution‐processed CIGS solar cells. The results demonstrate that the controllable formation of OVC phase approach should make a significant contribution to the efficiency promoting of solution processed CIGS solar cells. [ABSTRACT FROM AUTHOR]

A back contact interface in a kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic device plays an important role in fabricating high quality semiconducting photoactive layers and improving carrier extraction efficiency. However, uncontrolled decomposition reactions between the CZTSSe absorber layer and Mo electrode result in high series resistance and recombination at the back interface. The insertion of high work function MoO3 as an interfacial layer is considered as a promising way to engineer the back contact. This highlights the importance of elucidating the chemistry and dynamics of MoO3 at the Mo/kesterite interface in the CZTSSe annealing process. Herein, A detailed investigation of the elemental diffusion and chemistry of the back contact with the MoO3 intermediate layer during selenization is carried out. The results demonstrate that the presence of the MoO3 interfacial layer largely suppresses the chemical reaction between Mo and CZTSSe in the annealing process, inducing high quality CZTSSe absorbing films with fewer voids and reducing the thickness of MoSe2 from 209 to 84 nm when the optimized thickness of MoO3 is 10 nm. This finally leads to the increase in device efficiency from 9.02% to 10.92%, and the best performance where an efficiency of 11.37% is achieved. [ABSTRACT FROM AUTHOR]

The quaternary Cu 2 ZnSnS 4 (CZTS) QDs had been successfully introduced into quantum dot-sensitized solar cells (QDSC) via hydrolysis approach in our previous work [Green Chem. 2015, vol. 17, p. 4377], but the obtained cell efficiency was still limited by low open-circuit voltage and fill factor. Herein, we use 1-dodecanethiol (DDT) as capping ligand for fairly small-sized CZTS QDs synthesis to improve their intrinsic properties. Since this strong bonded capping ligand can not be replaced by 3-mercaptopropionic acid (MPA) directly, the nature cation (Cu, Zn or Sn)-DDT units of QDs are first exchanged by the preconjugated Cd-oleate via successive ionic layer adsorption and reaction (SILAR) procedure accompanied with the formation of a core/shell structure. The weak bonded oleic acid (OA) can be finally replaced by MPA and the constructed water soluble CZTS/CdSe QDSC achieves an impressive conversion efficiency of 4.70%. The electron transport and recombination dynamic processes are confirmed by intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS) measurements. It is found that the removal of long alkyl chain is conducive to improve the electron transport process and the type-II core/shell structure is beneficial to accelerate electron transport and retard charge recombination. This effective ligand removal strategy is proved to be more convenient for the applying of quaternary QDs in QDSC and would boost a more powerful efficiency in the future work. [ABSTRACT FROM AUTHOR]

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are two common subtypes of autoimmune bullous disease (AIBD). The key role of circulating autoreactive immune cells contributing to skin damage of AIBD has been widely recognized. Nevertheless, the immune characteristics in cutaneous lesions remain unclear. Here, we performed single-cell RNA sequencing (scRNA-seq) and single-cell VDJ sequencing (scRNA-seq) to generate transcriptional profiles for cells and T/B cell clonetype in skin lesions of BP and PV. We found that the proportions of NK&T, macrophages/ dendritic cells, B cells, and mast cells increased in BP and PV lesions. Then, BP and PV cells constituted over 75% of all myeloid cell subtypes, CD4+ T cell subtypes and CD8+ T cell subtypes. Strikingly, CD8+ Trm was identified to be expanded in PV, and located in the intermediate state of the pseudotime trajectory from CD8+ Tm to CD8+ Tem. Interestingly, CD8+ Tem and CD4+ Treg highly expressed exhaustion-related genes, especially in BP lesions. Moreover, the enhanced cell communication between stromal cells and immune cells like B cells and macrophages/ dendritic cells was also identified in BP and PV lesions. Finally, clone expansion was observed in T cells of BP and PV compared with HC, while CD8+ Trm represented the highest ratio of hyperexpanded TCR clones among all T cell subtypes. Our study generally depicts a large and comprehensive single-cell landscape of cutaneous lesions and highlights immune cell features in BP and PV. This offers potential research targets for further investigation. [ABSTRACT FROM AUTHOR]

[Display omitted] • An In element-buried CZITSSe/CZTSSe homojunction absorber is reconstructed. • The CZITSSe/CZTSSe homojunction generates shallow-level In Zn donors. • The In Zn donors suppress defect clusters and enlarge the surface band bending. • Achieve an active-area efficiency of 13.59 % with a high V oc of 0.527 V. The Cu 2 ZnSn(S,Se) 4 solar cells (CZTSSe) are emerging as a hot area of low-cost thin film photovoltaic technology owing to its non-toxicity and excellent photoelectric properties. However, the large open-circuit voltage deficit (V oc,deficit) caused by the inherently defective CdS/ CZTSSe heterojunction interface is still a huge challenge for improving power conversion efficiency. Herein, we reconstruct the heterojunction interface by inserting a CZTSSe:In into the CdS/CZTSSe heterojunction through an In 2 Se 3 post-deposition treatment. The local occupation of In3+ at Zn2+ and Sn4+ sites decreases the disordered Zn- and Sn-related deep defects and generates benign In Zn donors within CZITSSe transition layer simultaneously, which effectively enhances the surface p-to-n conversion. The combination of chemical and field-effect passivation regulates the charge extraction and passivates the charge recombination. As a result, the In element-buried absorber enables the V oc boost from 488 to 527 mV with an impressive active-area efficiency of 13.59 %. These results demonstrate the great potential of the In element-buried absorber in alleviating the V oc,deficit and enhancing the performance of CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

The doping of indium into absorber layer has been proven to be beneficial for hybrid buffer structured Cu 2 ZnSn(S, Se) 4 (CZTSSe) solar cells, but it is difficult to precisely control the doping content only relying on In diffusion from In 2 S 3 emitter. Herein, we use the solution method to prepare In-substituted CZTSSe layer by directly doping In 2 Se 3 into metal chalcogenides precursor solution. The doping content can be precisely controlled and the influences of indium doping on cell performance are systematically discussed. Mott-Schottky and resistivity measurements indicate that the carrier concentration and charge transport process are monotonically enhanced with increasing In/(In + Sn) content (0 at.%, 3 at.%, 6 at.% and 12 at.%). The improvements of series resistance also lead to a monotonic increase of fill factor ( FF ) from 52.1% to 64.8%. Due to the larger recombination at high doping content, the 6 at.% In content device finally contributes the highest power conversion efficiency of 8.47%. It is expected that a precisely controlled indium doping could further improve cell performance for efficient hybrid buffer structured devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A back surface field enhancement architecture is established in kesterite solar cells. • The hole doping of Mo(S,Se) 2 is realized by in-situ dopant with group VB elements. • Group VB elements doping further increase the work function and hole concentration. • The ohmic contact accelerates the holes extraction and minimizes recombination loss. One important issue limiting the development of Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells is the severe recombination loss at CZTSSe/Mo(S,Se) 2 /Mo back contact, primarily arising from the non-matched potential barrier and inferior electric contact between absorber and weak n -type Mo(S,Se) 2 interfacial layer. It is expected that a p-type Mo(S,Se) 2 can effectively improve the hole extraction and enhance the device performance. In this work, we propose a plausible direction to build up an electrically benign back surface field by in-situ doping Mo(S,Se) 2 with group VB elements (TM = V, Nb and Ta). It is turned out that the generated V Mo , Nb Mo , or Ta Mo shallow acceptors could convert Mo(S,Se) 2 from weak n -type to p-type conductivity and increase its work function (W F) and hole concentration. With the contact of p-type absorber (W F,absorber < W F,Mo(S,Se)₂), a benign ohmic contact with favorable downward band bending is formed, thereby accelerating the holes extraction and minimizing interface recombination loss. With significant gains in open-circuit voltage (V oc) and fill factor (FF), the Mo(S,Se) 2 :Ta device finally increases the efficiency from 10.82 % to 12.72 %. This convenient in-situ Mo(S,Se) 2 doping strategy is different from previous complicated or unstable cases and should serve as a basis for high-quality back contact engineering in kesterite photovoltaics. [ABSTRACT FROM AUTHOR]

Both recombination and band-edge shift are important factors for the open-circuit voltage ( V oc ) improvement of metal chalcogenide hole-transport material (HTM) based perovskite solar cells, but it is still not clear that which aspect plays the dominant role in such devices. Herein, we addressed this aspect through employing the band-tunable metal chalcogenide Cu 2 ZnSnS 4 (CZTS) QDs as HTM into perovskite solar cells. By replacing sulfur with selenium atom, the band gap of HTM was tuned from 1.64 eV to 1.14 eV and their influences on cell performances were further discussed. Though the Cu 2 ZnSnSe 4 (CZTSe) device with higher hole transport ability could improve the fill factor (FF), its V oc was still remarkably lower than that of the CZTS device. Electrochemical impedance spectroscopy (EIS) measurements indicated that the V oc loss (45 mV) induced by recombination here was far less than the V oc differences between the two devices (140 mV). After analyzing the band level alignment at TiO 2 /CH 3 NH 3 PbI 3 /HTM heterojunction, we proposed that the V oc enhancement of CZTS device was mainly ascribed to the more downward valence band-edge shift of HTM. This further approves that developing a wide band gap material without hindering charge injection is more pressing rather than depressing recombination process for future metal chalcogenide HTM researches. [ABSTRACT FROM AUTHOR]