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Chalcostibite CuSbS2 is a promising alternative absorber material for thin film solar cells but the poor photovoltaic device performance limits its wide application. In this work, one of the main loss mechanisms of structural defects such as voids and pin-holes has been investigated systematically via a quasi in situ method. Through studying the formation mechanisms of voids and pin-holes in CuSbS2 synthesized by sulfurizing a co-sputtered Cu–Sb metallic precursor, it is found that Cu vacancies can be formed and accumulated in preliminary voids as a result of the outward diffusion of Cu atoms during the heating process via the Kirkendall effect. Subsequently, the cracks between newly formed layers and small spaces caused by volume expansion further contributed to the final visible voids. In addition, two possible mechanisms, uneven grain growth of CuSbS2 and volume shrinkage estimated by the Pilling–Bedworth model, are proposed to explain the formation of pin-holes, paving the way to achieve high efficiency CuSbS2 solar cells. [ABSTRACT FROM AUTHOR]

Antimony selenosulfide, Sb2(S,Se)3, has emerged as a promising light-harvesting material due to its high absorption coefficient, suitable bandgap, and low-toxic and low-cost constituents. Previously, high-efficiency Sb2(S,Se)3 solar cells were fabricated exclusively using Spiro-OMeTAD as the hole-transporting layer (HTL) with an n–i–p device architecture. However, the poor stability and high cost of the widely used Spiro-OMeTAD hole-transporting material may restrict its potential large-scale applications in solar cells. Here, we report stable and high-efficiency all-inorganic Sb2(S,Se)3 solar cells enabled by an evaporated inorganic manganese sulfide (MnS) hole-transporting layer. MnS shows better valence band alignment with the Sb2(S,Se)3 absorber than Spiro-OMeTAD. With post-deposition heat treatment, MnS demonstrates increased carrier concentration and work function. These in turn result in the highest efficiency of 9.67% in all-inorganic Sb2(S,Se)3 solar cells. Moreover, the unencapsulated all-inorganic Sb2(S,Se)3 solar cell demonstrates a remarkably enhanced stability compared to the Spiro-OMeTAD-based cells. These exciting results illustrate that MnS possesses a larger efficiency potential than Spiro-OMeTAD. This low-cost, efficient, stable, and up-scalable MnS hole-transporting layer may also be applicable to other emerging solar cells, paving a better pathway toward commercialization. [ABSTRACT FROM AUTHOR]

Wide band gap pure sulphide kesterite Cu2ZnSnS4 is a promising environmentally friendly and low-cost photovoltaic material, which has attracted intense research interest. However, the record efficiency of solar cells based on Cu2ZnSnS4 absorbers just overcame the benchmark 10%, being far from the efficiency requirement for industrial-scale deployment. Recombination at the heterojunction interface accounts for a large proportion of the performance loss. Here we report a substantial improvement of the Cu2ZnSnS4 solar cell efficiency to over 10% enabled by modifying the Cu2ZnSnS4/Zn1−xCdxS heterojunction interface. We found that the introduction of the ammonium hydroxide during the Zn1−xCdxS deposition process can lead to a significant reduction of Zn related hydroxide and oxide impurities. The modified chemistry environment at the heterojunction interface facilitates the decrease of interface defects and promotes the interface microstructure quality. The improved heterojunction interface with suppressed interface recombination contributes to the enhanced open circuit voltage, fill factor and overall device performance. [ABSTRACT FROM AUTHOR]

Control over charge carrier transport in a low-temperature processed device is of key significance to realize high-performance perovskite solar cells (PSCs) and tandem solar cells. For low-temperature processed perovskite devices, a great challenge still remains due to the commonly inferior crystallinity and poor electron mobility of low-temperature processed electron transport materials. Meanwhile, electron transport layers (ETLs) produced at low-temperature show poor capability of managing the quality of overlying perovskite films, leaving abundant defects at grain boundaries, which hinder the efficient charge carrier transport or even result in severe energy loss by trap-assisted recombination. Here we present highly efficient PSCs realized by employing a tetramethylammonium hydroxide (TMAH) modified SnO2 ETL prepared at low-temperature (100–150 °C). TMAH modified SnO2 significantly enhances not only the conductivity of the SnO2 ETL for efficient electron extraction but also the electronic properties of the overlying perovskite film for fast electron transport across the grain boundaries. With this proposed novel ETL, an average efficiency above 20% is achieved for the low-temperature-processed PSCs, with an even higher efficiency exceeding 21% for the champion device. These low-temperature processed PSC devices also show reliable reproducibility and stability. [ABSTRACT FROM AUTHOR]

An innovative approach to overcome the main challenge of solution-based pure-sulfide Cu2ZnSnS4 thin film solar cells by sulfurizing quaternary Cu2ZnSnS4 nanocrystals into nearly micron-sized large grains in a few minutes is presented. We developed an efficient phase-transition-driven grain growth strategy to explore the application of metastable wurtzite Cu2ZnSnS4 nano-materials in the photovoltaic field. The obtained Cu2ZnSnS4 thin film has a typical bilayer microstructure containing large grains on the top and fine grains at the bottom. Clear variations of phase, morphology, and component redistribution of the Cu2ZnSnS4 thin film were identified after the sulfurization process, which is critical to get a dense large-grained Cu2ZnSnS4 layer from quaternary nanocrystals. By tuning the composition of the wurtzite Cu2ZnSnS4 nanocrystals, annealing conditions, and sodium-containing compound, laboratory-scale photovoltaic cells with 4.83% efficiency were demonstrated without anti-reflection coatings. These results suggest the potential application of metastable wurtzite nanocrystals in pure-sulfide Cu2ZnSnS4 solar cells. This unique approach may also open up new opportunities to other optoelectronic devices, such as CuIn(S,Se)2, Cu2(In,Ga)Se4, CdTe, and Cu2ZnGe(S,Se)4 solar cells. [ABSTRACT FROM AUTHOR]

Earth-abundant Cu2ZnSnS4 (CZTS) has been confirmed as a promising semiconductor material for thin film solar cells. To meet the requirements of high-efficiency and low-cost for photovoltaic technologies, a modified thermal decomposition sol–gel method with low-cost and low-toxicity for CZTS thin film preparation is presented, and the detailed formation mechanism of the thin film is investigated to obtain an optimized process. By introducing non-aqueous thiourea–metal–oxygen sol–gel processing, as well as applying extrinsic dopants and chemical etching, high-quality and phase-controlled CZTS thin films with homogeneous elemental distribution and a low impurity content have been synthesized. Based on the modified sol–gel method, solar cells with a structure of Ni:Al/ZAO/i-ZnO/CdS/CZTS/Mo/glass have been fabricated, and a power conversion efficiency of 5.10% is obtained, indicating its potential for high-throughput and high power conversion efficiency photovoltaic devices. [ABSTRACT FROM AUTHOR]