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We report the fabrication and optimization of multipass inkjet-printed perovskite solar cells. The presented process allows excellent control of crystallization dynamics and thickness of the perovskite layer. In order to obtain a homogenous perovskite film of large and densely packed crystals on a planar TiO2 electron transport layer we make use of an additional vacuum annealing step. Its beneficial impact was characterized in terms of device performance and laser beam induced current mapping as well as atomic force microscopy. The optimized fabrication methods resulted in power conversion efficiencies up to 11.3% of multipass inkjet printed perovskite solar cells. The spin coated reference devices reached 12.8% power conversion efficiency. With these first results, we advance the field of digital printing techniques for perovskites and demonstrate a major step towards highly efficient, low-cost and less Pb-waste producing perovskite solar cells. [ABSTRACT FROM AUTHOR]

Based on solution-processed kesterite-type Cu2ZnSn(S1- x,Se x)4 solar cells, a detailed investigation of the source and effects of sodium in the absorber will be presented. In contrast to most investigations in literature so far, the main process for sodium supply during selenization does not seem to be the diffusion out of the sodium-containing glass substrate but a transfer from the environment into the absorber. Studies on the influence of sodium on the morphological properties of the absorbers let us assume that the formation of big grains is not necessarily coupled to the presence of sodium during selenization. However, a beneficial effect on the electrical properties can mainly be seen in the open-circuit voltage ( Voc) and the fill factor (FF) which should be related to an increase in doping concentration ( NA). [ABSTRACT FROM AUTHOR]

Cu2ZnSnSe4 (CZTSe) thin films are prepared by a two-step method which involves co-evaporation of Cu, Zn, Sn, and Se on molybdenum-coated soda-lime glass at low substrate temperature and a following selenization. Solar cells with efficiencies of up to 6.5% can be achieved. The influence of the selenium deposition rates during co-evaporation and the nitrogen pressure during selenization on the properties of the CZTSe films are investigated. It is found that these two parameters can significantly affect the morphology and crystallinity of the CZTSe films. The possible reasons for the experimental results are discussed. [ABSTRACT FROM AUTHOR]

We report on order-disorder related band gap changes in Cu2ZnSn(S,Se)4 solar cells which are induced by post-annealing. The band gap changes of the absorber are detected utilizing electroreflectance and analyzed by comparison with predictions of the stochastic Vineyard model. This yields a critical temperature of TC = 195°C above which the Cu2ZnSn(S,Se)4 absorber layer is entirely disordered within the Cu-Zn layers of the kesterite unit cell. The temporal evolution of the band gap during annealing shows that the equilibrium value is reached on a timescale in the order of hours, depending on the annealing temperature. In contrast to other experimental techniques, electroreflectance precisely measures the band gap and is not influenced by defect-mediated radiative recombination. [ABSTRACT FROM AUTHOR]

Transferring the high power conversion efficiencies (PCEs) of spin‐coated perovskite solar cells (PSCs) on the laboratory scale to large‐area photovoltaic modules requires a significant advance in scalable fabrication methods. Digital inkjet printing promises scalable, material, and cost‐efficient deposition of perovskite thin films on a wide range of substrates and in arbitrary shapes. In this work, high‐quality inkjet‐printed triple‐cation (methylammonium, formamidinium, and cesium) perovskite layers with exceptional thicknesses of >1 µm are demonstrated, enabling unprecedentedly high PCEs > 21% and stabilized power output efficiencies > 18% for inkjet‐printed PSCs. In‐depth characterization shows that the thick inkjet‐printed perovskite thin films deposited using the process developed herein exhibit a columnar crystal structure, free of horizontal grain boundaries, which extend over the entire thickness. A thin film thickness of around 1.5 µm is determined as optimal for PSC for this process. Up to this layer thickness X‐ray photoemission spectroscopy analysis confirms the expected stoichiometric perovskite composition at the surface and shows strong deviations and inhomogeneities for thicker thin films. The micrometer‐thick perovskite thin films exhibit remarkably long charge carrier lifetimes, highlighting their excellent optoelectronic characteristics. They are particularly promising for next‐generation inkjet‐printed perovskite solar cells, photodetectors, and X‐ray detectors. [ABSTRACT FROM AUTHOR]

Keywords: all-perovskite tandem solar cells; large grain; low-bandgap perovskites; solar cells; vacuum-assisted growth control This efficient low-bandgap perovskite solar cells enable achieving efficient all-perovskite tandem solar cells. All-perovskite tandem solar cells, large grain, low-bandgap perovskites, solar cells, vacuum-assisted growth control. [Extracted from the article]

Abstract: A low-cost method has been developed to fabricate Cu2ZnSn(S,Se)4 solar cells. By this method, firstly SnS, CuS, and ZnS layers are successively deposited on a molybdenum/soda lime glass (Mo/SLG) substrate by chemical bath deposition. The Cu2ZnSn(S,Se)4 thin films are obtained by annealing the precursor in a selenium atmosphere utilizing a graphite box in the furnace. The obtained Cu2ZnSn(S,Se)4 thin films show large crystalline grains. By optimizing the preparation process, Cu2ZnSn(S,Se)4 solar cells with efficiencies up to 4.5% are obtained. The results imply that the Cu2ZnSn(S,Se)4/CdS interface and the back contact may be limiting factors for solar cell efficiency. [Copyright &y& Elsevier]

Hybrid organic-inorganic perovskites are highly promising candidates for the upcoming generation of single- and multijunction solar cells. Despite their extraordinarily good semiconducting properties, there is a need to increase the intrinsic material stability against heat, moisture, and light exposure. Understanding how variations in synthesis affect the bulk and surface stability is therefore of paramount importance to achieve a rapid commercialization on large scales. In this work, we show for the case of methylammonium lead iodide that a thorough control of the methylammonium iodide (MAI) partial pressure during co-evaporation is essential to limit photostriction and reach phase purity, which dictate the absorber stability. Kelvin probe force microscopy measurements in ultrahigh vacuum corroborate that off-stoichiometric absorbers prepared with an excess of MAI partial pressure exhibit traces of low-dimensional (two-dimensional, 2D) perovskites and stacking faults that have adverse effects on the intrinsic material stability. Under optimized growth conditions, time-resolved photoluminescence and work functions mapping corroborate that the perovskite films are less prone to heat and light degradation.