Organic–inorganic hybrid halide perovskites are proven to be a promising semiconductor material as the absorber layer of solar cells. However, the perovskite films always suffer from nonuniform coverage or high trap state density due to the polycrystalline characteristics, which degrade the photoelectric properties of thin films. Herein, the alkali metal ions which are stable against oxidation and reduction are used in the perovskite precursor solution to induce the process of crystallization and nucleation, then affect the properties of the perovskite film. It is found that the addition of the alkali metal ions clearly improves the quality of perovskite film: enlarges the grain sizes, reduces the defect state density, passivates the grain boundaries, increases the built‐in potential (V bi), resulting to the enhancement in the power conversion efficiency of perovskite thin film solar cell.

Electron transport layer (ETL), facilitating charge carrier separation and electron extraction, is a key component in planar perovskite solar cells (PSCs). We developed an effective ETL using low-temperature solution-processed Nb-doped SnO (Nb:SnO). Compared to the pristine SnO, the power conversion efficiency of PSCs based on Nb:SnO ETL is raised to 17.57% from 15.13%. The splendid performance is attributed to the excellent optical and electronic properties of the Nb:SnO material, such as smooth surface, high electron mobility, appropriate electrical conductivity, therefore making a better growth platform for a high quality perovskite absorber layer. Experimental analyses reveal that the Nb:SnO ETL significantly enhances the electron extraction and effectively suppresses charge recombination, leading to improved solar cell performance.

Homogeneous molecular precursor solutions are excellent choices for obtaining smooth absorber layers, and they offer the potential to significantly lower the manufacturing cost of solar cells. Here, we present a thermally degradable metal butyldithiocarbamate-based solution approach to fabricate Cu2ZnSn(S,Se)4 solar cells. Low-cost Cu2O, ZnO, and SnO were used as the starting materials and were dissolved in the ethanol solution of butyldithiocarbamic acid. By tuning the composition of the Cu2ZnSn(S,Se)4 thin film, a power conversion efficiency of 6.03% on the basis of the active area has been achieved.

We developed a versatile and environmentally friendly solution approach for the fabrication of a variety of metal sulfide nanocrystal thin films. Metal oxides, metal hydroxides, metal chlorides, metal acetates, and metal acetylacetonates can be used as the starting materials and dissolved in thioglycolic acid and ethanolamine, forming many types of metal–organic precursor solutions. High quality CdS, SnS, CuInS2, CuSbS2, Cu2ZnSnS4, Cu­(In0.7Ga0.3)­S2, and luminescent Ag-doped Zn x Cd1–x S nanocrystal thin films have been successfully prepared by spin-coating their corresponding metal precursor solutions. Cu2ZnSn­(S,Se)4 thin film solar cell with a power conversion efficiency of 6.83% has been realized by this versatile method.

Over the past few years, we have witnessed the occurrence and progress of CsPbI3 semiconductor material as a superstar in the photovoltaic fields. By virtue of its excellent photoelectric properties,...

efficiency of laboratory-scale all-inorganic solar cells has been improved to 20.37%, [5] approaching ~70% of the efficiency limit based on the Shockley-Queisser (S-Q) theory. [9][10][11] Among all the high-performance all-inorganic perovskite devices, the photocurrent and fill factor have exceeded 95% and 90% of their theoretical S-Q limits, respectively, while the open-circuit voltage (V oc ) falls at ≈80% of the limit. Therefore, there is relatively larger room for improvement in the V oc for yielding higher power conversion efficiency (PCE). [5,[12][13][14][15] The V oc depends on the dynamics of charge carrier recombination, which is connected to the non-radiative recombination processes. [16][17][18][19] Defects usually scatter the carriers as non-radiative recombination reaction centers. [20][21][22][23] Therefore, preparing high-quality perovskite films with low-defect density is a prerequisite for high-performance photovoltaic devices. The quality of the perovskite active layer can be manipulated by the crystallization processes, thus dynamic control of crystallization appears to be very important. In a common solvent crystallization process, the perovskite grain growth is mainly completed in the initial solvent evaporation process because: 1) solvent evaporation leads to the super-saturation of the solute, producing a mass of seed crystals; 2) solvent evaporation drives the migration of the perovskite precursor colloids, which is beneficial to the grain growth. Subsequent extended annealing has faint effect on the grain growth. We assumed that if the "reactive solvent medium" can remain for a longer time, the colloids will react completely and the grains can merge better. Inspired by this idea, we consider molten salt (MS) synthesis, a classical method for preparing functional materials owing to its simplicity, speed, large-scale compatibility, and low cost. [24][25][26][27][28] The MS melts can exhibit homogeneous heat and mass transfer to carry out chemical transformation even at low temperature. [24,29] MS methods have been widely used in industrial production. For example, they are regarded as ideal reactors for the closed Th-U cycle due to their lower fissile inventory [30] and are applied in lignite pyrolysis to affect the products. [31] The MS processes have been applied not only in chemical reactions but also in material morphology manipulation. [32][33][34] So far, MS can be classified into two types: solid high-temperature MS, [27,34,35] and low-temperature MS (ionic liquids [ILs]) [32,36,37] depending on their states within a certain temperature range. The solid MSs show high ionic conductivity only in the liquid state, and thereby should be used at high temperatures above their melting points. ILs are considered Dynamic manipulation of crystallization is pivotal to the quality of polycrystalline films. A molten-salt-assisted crystallization (MSAC) strategy is presented to improve grain growth of the all-inorganic perovskite films. Compared with the traditional solvent annealing, MSAC enables...

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Solution deposition approaches play an important role in reducing the manufacturing cost of Cu2ZnSnSe4 (CZTSe) thin film solar cells. Here, we present a novel precursor-based solution approach to fabricate highly efficient CZTSe solar cells. In this approach, low-cost elemental Cu, Zn, Sn, and Se powders were simultaneously dissolved in the solution of thioglycolic acid and ethanolamine, forming a homogeneous CZTSe precursor solution to deposit CZTSe nanocrystal thin films. Based on high-quality CZTSe absorber layer, pure selenide CZTSe solar cell with a photoelectric conversion efficiency of 8.02% has been achieved without antireflection coating.