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SnO 2 has gathered wide attention as an electron transport layer (ETL) in perovskite solar cells (PSCs) for its outstanding properties such as low-temperature process, high mobility, and matched energy level. However, the low-temperature annealing of SnO 2 may lead to the formation of large quantities of oxygen vacanices, which can give rise to nonradiative recombination. Herein, we introduce an alanine (C 3 H 7 NO 2) with a high fusion point to modify the quality of SnO 2 film in solution processing at a low temperature. The carboxylic acid group of alanine can crosslink to SnO 2 via a chelating interaction, leading to the decreasing in traps and increasing in carrier transmission. Furthermore, the amino group of alanine could also promote the crystallization and suppress ion migration of the perovskite film through hydrogen bonds. The result demonstrates that using the C 3 H 7 NO 2 modified SnO 2 ETL with the optimal concentration, the highest power conversion efficiency (PCE) of carbon-based CsPbIBr 2 PSC was obviously improved from 5.09% to 6.80%, leading to an increase by almost 33.60% compared to the PSC with pristine SnO 2. More importantly, the PSCs with modified SnO 2 had better long-term stability. This paper demonstrates the utility of the alanine modification approach boosting the performance of carbon-based PSCs. [ABSTRACT FROM AUTHOR]

Carbon-based, all-inorganic CsPbIBr 2 perovskite solar cells (PSCs) have demonstrated to have superior stability and low cost, combine with a simple fabrication process. However, there are two vital factors that impede enhancement of the power conversion efficiency (PCE) of PSCs. One is the low energy level alignment matching between perovskite layer and carbon electrode, and the other one is defects of the perovskite film. Here, we introduce CsPbI 2 Br QDs as an interface between the CsPbIBr 2 layer and carbon electrode to passivate the perovskite bulk film. The surface defects and charge carrier mobility of QDs are also modified using a bidentate chelating ligand, namely 4-mercaptobenzoic acid (4-MBA). By optimizing the energy level alignment at the interface, the hole extraction is promoted, and interfacial recombination is suppressed. Compared to the PSCs without the QDs layer, the QDs-passivated PSC achieved a PCE of 6.69%, leading to an increase of almost 31.43%. Furthermore, the PSCs with QDs passivation had better water resistance. This work provides a promising strategy to enhance both the stability and efficiency of carbon-based PSCs. Carbon-based, all-inorganic CsPbIBr 2 perovskite solar cells (PSCs) have been demonstrated to have superior stability and low cost, combine with simple fabrication process. However, the low energy level alignment matching between perovskite layer and carbon electrode and defects of the perovskite film impede enhancement of the power conversion efficiency (PCE) of PSCs. Here, we introduce CsPbI 2 Br QDs as an interface between the CsPbIBr 2 layer and carbon electrode to passivate the perovskite bulk film. The surface defects and charge carrier mobility of QDs are also modified by using a bidentate chelating ligand, namely 4-mercaptobenzoic acid (4-MBA). By optimizing the energy level alignment at the interface, the hole extraction is promoted and interfacial recombination is suppressed. Compared to the PSCs without QDs layer, the QDs-passivated PSC achieved a PCE of 6.69%, leading to an increase by almost 31.43%. Furthermore, the PSCs with QDs passivation had better water resistance. This work provides a promising strategy to enhance both the stability and efficiency of carbon-based PSCs. [Display omitted] • CsPbI 2 Br QDs were introduced as an interface to passivate the CsPbIBr 2 bulk film. • The surface defects and charge carrier mobility of QDs are modified by using a bidentate chelating ligand. • The optimized energy level alignment at the interface of CsPbIBr 2 /CsPbI 2 Br QDs resulted in the promoted hole extraction. • The QDs-passivated PSC achieved a PCE of 6.69%, leading to an increase by almost 31.43% compared with the pristine PSC. • The PSCs with QDs passivation had better water resistance. [ABSTRACT FROM AUTHOR]

Recently, inorganic perovskite materials have attracted extensive attention due to their advantages such as excellent photoelectric performance, adjustable band gap and simple preparation process. At present, the photoelectric conversion efficiency of inorganic perovskite solar cells have exceeded 19.0%. However, there are many kinds of defects on the surfaces and grain boundaries of the perovskite films, which seriously affect the efficiency and stability of the device. Therefore, how to effectively control the crystallization process and passivate the surface defects of the inorganic perovskite films are challenges in this field. In this paper, by analyzing the types and mechanism of inorganic perovskite film defects, the influence of inorganic perovskite film preparation technique on crystallization in recent years is reviewed, passivation strategies for different kinds of additives are discussed in combination with Lewis acid base theory, and interface engineering on both sides of the perovskite film is summarized. Finally, the future research emphasis of inorganic perovskite solar cell is prospected. [ABSTRACT FROM AUTHOR]

The all-inorganic perovskite CsPbIBr2 is a promising material in the photovoltaic (PV) field due to its acceptable optical bandgap and favorable air-stable phase stability. However, the conventional solution-processed poor-coverage thin films make it a challenging task to prepare high-performance solar cells. In this work, we introduce cadmium ions (Cd2+) into CsPbIBr2 perovskite and investigate how this doping treatment would affect the PV performance of the carbon-based CsPbIBr2 all-inorganic perovskite solar cells (FTO/SnO2/CsPbIBr2/carbon). We found that the crystallinity and morphology of CsPbIBr2 thin films are significantly improved after Cd2+ doping, leading to improved light absorption and carrier transportation with reduced carrier recombination in perovskites. The optimized device achieved the highest efficiency of 6.79% in comparison with 4.36% for the device without Cd2+ doping, an increase of 56% in efficiency. Meanwhile, the optimized device with Cd2+ doping exhibited enhanced stability (76% of initial efficiency after 10 hours) in ambient atmosphere. Furthermore, the whole fabrication process of these devices is performed at low temperatures, not more than 160 °C. The present work provides a simple and economical strategy for the fabrication of low-temperature-processed CsPbIBr2 solar cells and the improvement in their performance. [ABSTRACT FROM AUTHOR]

In recent years, all-inorganic perovskite cells (PSCs) have been widely studied by researchers because of their excellent thermal and optical stability. Among them, the CsPbIBr 2 PSCs with carbon electrode have attracted extensive attention because of its excellent stability, low preparation difficulty, easy commercialization and low cost. However, the crystal quality of CsPbIBr 2 film is poor. There are a large number of pinholes and surface defects (Pb2+ exposure), which will lead to internal short circuit and a large number of nonradiative recombination, thus affecting the photoelectric conversion efficiency (PCE). Although these problems can be improved by antisolvent engineering, the traditional antisolvent chlorobenzene (CB) and toluene (TL) are highly toxic and harmful to the environment. In this paper, isopropanol (IPA) is used as a green antisolvent to improve the quality of CsPbIBr 2 films, and S2− with strong reducibility and passivation defects are successfully introduced into the CsPbIBr 2 film surface by further adding thiourea as Lewis base to IPA (IPA-S). After the CsPbIBr 2 films were treatment by IPA-S antisolvent, we successfully obtained high-quality CsPbIBr 2 films with large grain size and no pinholes. Moreover, through XPS, PL, EIS and other tests, it is found that the S2− introduced by IPA-S can combine with the exposed Pb2+ on the CsPbIBr 2 surface to passivate the defects, it is beneficial to reduce the non-radiative recombination and improve the transport capacity of carriers. Finally, the results of this paper prove that that the champion PCE of carbon based CsPbIBr 2 PSCs treated with IPA-S antisolvent was 6.79%, which was nearly 30% higher than the original carbon based CsPbIBr 2 PSCs. In addition, due to the strong reducibility of S2−, the carbon based CsPbIBr 2 PSCs treated with isopropanol antisolvent added with thiourea can continue to work in air with 40% relative humidity, and the efficiency can remain 85% within 10 days. In order to improve the performance and stability of the all-inorganic PSCs, this paper provides a non-toxic, environmentally friendly and effective scheme. [ABSTRACT FROM AUTHOR]

SnO 2 has been widely used in perovskite solar cells (PSCs) and LEDs as a flat electron transport layer (ETL), because of its low preparation temperature and low energy consumption. However, electrons are easily captured by defects on the ETL, resulting in ion migration of perovskite, which increases the extensive hysteresis index (HI) of PSCs. By preparing surface microstructures (such as mesoporous structure and nanowire array) on the ETL, the electron transmission capacity can be improved effectively, which reduces the HI and increases photoelectric conversion efficiency (PCE). In this paper, we use a simple and high fault-tolerant method to prepare the SnO 2 ETL with nanopore structure (NP–SnO 2) at low temperature. The polystyrene microsphere sphere templates were prepared on flat SnO 2 film by a vertical deposition method, and then SnO 2 films with NP-SnO 2 were prepared by template method. The size and density of nanopores in the NP-SnO 2 are controlled by controlling the size of PS spheres and the concentration of PS colloidal solution. The nanopores structure could improve the quality of CsPbIBr 2 crystal films. Moreover, the nanopore structure can increase the contact area between the SnO 2 ETL and the CsPbIBr 2 film, which provides more channels for electron transmission. The results show that CsPbIBr 2 PSCs based on NP-SnO 2 ETL can obtain the champion PCE, which is 6.68% (25.33% higher than the PSCs based on flat SnO 2 ETL), and the HI of the PSCs based on NP-SnO 2 ETL was reduced from 0.36 to 0.17. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the dripping temperature of the precursor solution on the quality of the Cs 2 AgBiBr 6 film was studied in detail. It can be concluded that the Cs 2 AgBiBr 6 film's quality is the best when the dripping temperature is 65 °C. To further study the influence of the quality of the Cs 2 AgBiBr 6 film on the performance of perovskite PSCs, an HTL-free carbon-based PSC with Cs 2 AgBiBr 6 as a light absorbing layer was fabricated. The photoelectric test results show that the Cs 2 AgBiBr 6 carbon-based PSC prepared at 65 °C has the best performance and the PCE of 0.54% is attained, which is 27% higher than that prepared at 25 °C. This work provides valuable guidance for the preparation of high-quality Cs 2 AgBiBr 6 film by one-step method. In this paper, the effect of the dripping temperature of the precursor solution on the quality of the Cs 2 AgBiBr 6 film was studied in detail. It can be concluded that the Cs 2 AgBiBr 6 film's quality is the best when the dripping temperature is 65 °C. To further study the influence of the quality of the Cs 2 AgBiBr 6 film on the performance of perovskite PSCs, an HTL-free carbon-based PSC with Cs 2 AgBiBr 6 as light absorbing layer was fabricated. The photoelectric test results show that the Cs 2 AgBiBr 6 carbon-based PSC prepared at 65 °C has the best performance and the PCE of 0.54% is attained, which is 27% higher than that prepared at 25 °C. This work provides valuable guidance for the preparation of high-quality Cs 2 AgBiBr 6 film by one-step method. [Display omitted] • The quality of Cs 2 AgBiBr 6 film was improved by changing the dripping temperature of the precursor solution. • The effect of the dripping temperature of precursor solution on the nucleation mechanism of PSCs was studied. • The carbon-based PSC prepared at 65 °C has the best performance and the PCE of 0.54% is attained, which is 27% higher than that prepared at 25 °C. [ABSTRACT FROM AUTHOR]