SnO2-based Perovskite Solar Cells Research Articles

Polymer-Doped SnO2 as an Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Cells.

To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO2-perovskite interface in SnO2-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO2 electron transport layer, a novel polymer-doped SnO2 matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO2 colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO2 solution. As a result of the polymer addition, the density and wetting properties of the SnO2 layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO2 and Spiro-OMeTAD layers and using (FAPbI3)0.97(MAPbBr3)0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells.

Multifunctional buried interface modification for efficient and stable SnO2-based perovskite solar cells

HEDTA-3Na is employed to modify the buried interface for fabricating efficient and stable SnO2-based perovskite solar cells.

Facilitating the formation of SnO2 film via HfO2-modified FTO electrode for efficient perovskite solar cells

Fabricating a dense and crystalline SnO2 film has been an important step for efficient SnO2-based perovskite solar cells (PSCs). Herein, a wide bandgap material, HfO2, was deposited on the surface of FTO to facilitate the formation of an SnO2 film. It was found that the HfO2 modification on FTO could significantly improve the crystallization of the upper SnO2 film and passivate the trap states within the SnO2 layer. Moreover, the high conduction band level of HfO2 can block the backflow of electrons and suppress the nonradiative recombination of carriers. Eventually, the best PSC with HfO2 interlayer presented a power conversion efficiency (PCE) of 21.13% with a VOC of 1.13 V, which are higher than those of the reference device. This study provides a meaningful strategy for ETL optimization to further increase the efficiency of the SnO2-based PSCs.

4-Trifluorophenylammonium Iodide-Based Dual Interfacial Modification Engineering toward Improved Efficiency and Stability of SnO2-Based Perovskite Solar Cells.

Passivation engineering has been identified as an effective strategy to eliminate the targeted interfacial defects for improving the efficiency and stability of perovskite solar cells (PSCs). Herein, 4-trifluorophenylammonium iodide (CF3PhAI) is presented as a multifunctional passivation agent to modify buried SnO2/perovskite and perovskite/hole transport layer (HTL) interfaces. Upon incorporation of CF3PhAI between SnO2 and perovskite, CF3PhAI can chemically link to SnO2 via Lewis coordination and electrostatic coupling, thereby effectively passivating under-coordinated Sn and filling the oxygen vacancy. Meanwhile, CF3PhAI helps anchor PbI2 and organic cations (MA+/FA+) to control the crystallization of the perovskite. Consequently, reduced interfacial defects, homogeneous perovskite crystallites, and better energetic alignment can be simultaneously achieved. When CF3PhAI was further used to modify the perovskite/HTL interface, the fabricated PSCs yielded an impressive power conversion efficiency of 23.06% together with negligible J-V hysteresis. The unencapsulated devices exhibited long-term stability in wet conditions (91.8% efficiency retention after 1000 h) due to the water-resistant CF3PhAI. We also achieved good light soaking stability, maintaining 86.1% of its initial efficiency after aging for 720 h. Overall, our finding provides a promising strategy for modifying the dual contact interfaces of PSCs toward improved efficiency and stability.

Dually-passivated planar SnO2 based perovskite solar cells with ˃2,700h ambient stability: Facile fabrication, high performance and mechanism

In SnO2-based planar perovskite solar cells (SP–PSCs), stability issue derived by defects at grain boundaries (GBs) and surface in perovskite films has been one of the main reasons that limit its commercialization. Therefore, co-passivation of both defects is pivotal to maximize passivation effects for improving power conversion efficiency (PCE) and stability, which is rarely reported in SP-PSCs. Herein, two simple passivating agents including Pb(SCN)2 and choline chloride (ChCl) were selected to dually passivate GBs and surface defects in the perovskite films (ambient atmosphere), respectively. The influences of co-passivation on PCE and ambient stability of devices were intensively studied, and the related mechanisms were also elucidated in detail. The dually-passivated device obtained a champion PCE of 19.98%, and maintained about 94% of the initial efficiency after being stored for ˃2700h aging in the humid air. The reduction of GBs and surface defects not only weakens the non-radiative recombination of carriers, but also inhibits the penetration of moisture and oxygen, which ultimately greatly enhances the PCE and stability of the device. This paper provides support for the dual passivation of GBs and surface defects to ameliorate ambient stability of the SP-PSCs, and also enriches the selectivity of passivation agents on dual passivation.

Highly improved efficiency and stability of planar perovskite solar cells via bifunctional phytic acid dipotassium anchored SnO2 electron transport layer

The defects at the interface of SnO2 electron transport layers (ETLs) /perovskite layer hinder extraction and transfer of charge, which restrict the further improvement of the photoelectric conversion efficiency (PCE) of SnO2-based perovskite solar cells (PSCs). Herein, an effective bifunctional anchoring strategy is developed to passivate SnO2/perovskite interface defects by adequate chelate sites in polydentate phytic acid dipotassium (PAD) to anchor SnO2 colloids. It is confirmed that polydentate PAD anchoring can form new Sn-O-P bonds with uncoordinated Sn2+, which can efficiently passivate the SnO2 surface defects and alleviate the interfacial charge recombination between SnO2 and perovskite layer. The reduction of SnO2 surface defects enhances the electron transport efficiency and increases the conductivity of the PAD-SnO2 ETLs to 2.1 times that of SnO2 ETLs. Meanwhile, the anchoring group potassium ions (K+) in PAD can promote the in-plane growth of perovskite grains and increase the average grain size of perovskite from 560 nm to 850 nm. As a consequence, the PCE of the PAD-SnO2-based PSCs increased sharply to 21.61%, which is 10.7% higher than that of the PSCs made with SnO2 ETLs (19.52%). The unencapsulated PSCs deposited on PAD-SnO2 ETLs can remain 99.5% of their initial efficiency after 60 days under 25–30% humidity.

Study of black phosphorus quantum dot modified SnO2-based perovskite solar cells

Organic–inorganic hybrid perovskite solar cells are considered promising due to their strong light absorption capability, long carrier diffusion distance, and rapid increase in energy conversion efficiency in the past decade. However, there is a high concentration of defects between the perovskite layer and the electron transport layer, which can lead to limited carrier extraction and, thus, affect the device efficiency. Black phosphorus quantum dots (BPQDs) have the advantages of tunable bandgap size, high absorption coefficient, and high electron mobility. Therefore, we introduced black phosphorus quantum dots (BPQDs) in aqueous SnO2 colloidal solution by laser liquid-phase ablation to improve the carrier extraction rate and reduce the trap density. By characterizing the prepared complete devices, we found that the device efficiency reached 15.83% after the introduction of BPQDs, which is 12% higher compared to 14.06% for the blank sample. Our work provides a simple and fast method to enhance the efficiency of perovskite solar cells.

Dispersed SnO2 colloids using sodium dodecyl benzene sulfonate for high-performance planar perovskite solar cells

Recently, SnO2-based perovskite solar cells (PSCs) have become more promising than traditional-material-based PSCs because of their simple low-temperature solution approach and low cost; meanwhile, the high-temperature process of mesoporous TiO2-based PSCs still offers a higher power conversion efficiency (PCE). In planar-based PSCs, nonradiative recombination of electron-hole pairs at the SnO2/perovskite interface leads to a loss of potential and a reduced PCE. Here, the SnO2-SDBS electron transport layer (ETL) is employed in PSCs to depress the defects of the SnO2 layer and the grain boundaries of the perovskite film. The surfactant SDBS was used as a wetting agent for SnO2 nanoparticles, to improve dispersibility. In addition, the benzene sulfonic acid group of SDBS attached to the SnO2-SDBS film can control the process of perovskite crystallization, producing a vertically aligned growth and large-grain perovskite layer. Finally, the open-circuit voltage was improved from 1.038 to 1.077 V and the PCE increased from 18.01% to 19.25% in the devices using the SnO2-SDBS ETL. The incorporation of SnO2-SDBS as an ETL paves the way to further performance enhancements of SnO2-based planar PSCs.

High-effective SnO2-based perovskite solar cells by multifunctional molecular additive engineering

The electron transport layer (ETL) is one of the most important factors to determine the photovoltage (PV) performance of perovskite solar cells (PSCs), and defects and non-radiative recombination are the negative factors limiting the efficiency improvement of PSCs. Herein, using tin oxide (SnO2) as the electron transport layer and multiple functional groups organic molecule of 3-(formamidinothio)-1-propanesulfonic acid (FTPS) as additive of SnO2, we fabricated a high-effective SnO2-based planar PSC. The introduction of FTPS reduces the oxygen vacancy defects of SnO2 ETLs and accommodates perovskite crystal growth on it. The modification of FTPS improves the conductivity and the electron extraction ability of SnO2, mitigates the trap-state density and carrier non-radiative recombination at the interfaces of SnO2/perovskite. As a result, the PSC based on pristine SnO2 ETL obtains a power conversion efficiency (PCE) of 20.49%, while the champion device based on SnO2 + FTPS (0.3 mg/mL) ETL achieves an efficiency of 22.52% with insignificant hysteresis effect and excellent stability. This effective defect passivation strategy work provides a promising low-cost technology for the preparation of planar PSCs with high efficiency and stability.

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

Summary Capacitance-based techniques have been used to measure the electrical properties of halide perovskite solar cells (PSCs) such as defect activation energy and density, carrier concentration, and dielectric constant, which provide key information for evaluating the device performance. Here, we show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface, because the high-frequency capacitance signature is due to the response of charge carriers in the hole-transport layer (HTL). For HTL-free PSCs, high-frequency capacitance can be considered as the geometric capacitance for analyzing the dielectric constant of the perovskite layer because there is no trapping and de-trapping of charge carriers in the perovskite layer. We further find that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer, but the overlapping effects with charge transport materials must be avoided.

Band Alignment Engineering between Planar SnO2 and Halide Perovskites via Two-Step Annealing.

Managing defects in SnO2 is critical for improving the power conversion efficiency (PCE) of halide perovskite-based solar cells. However, typically reported SnO2-based perovskite solar cells have inherent defects in the SnO2 layer, which lead to a lower PCE and hysteresis. Here, we report that a dual-coating approach for SnO2 with different annealing temperatures can simultaneously form a SnO2 layer with high crystallinity and uniform surface coverage. Along with these enhanced physical properties, the dual-coated SnO2 layer shows favorable band alignment with a mixed halide perovskite. After careful optimization of the dual-coating method, the average PCE of the perovskite solar cell based on the dual-coated SnO2 layer increases from 18.07 to 19.23% with a best-performing cell of 20.03%. Note that a facile two-step coating and annealing method can open new avenues to develop SnO2-based perovskite solar cells with stabilized and improved photovoltaic performances.

Ethyl acetate green antisolvent process for high-performance planar low-temperature SnO2-based perovskite solar cells made in ambient air

One-step antisolvent deposition has been considered as one of the most feasible methods to obtain high-performance perovskite solar cells (PSCs). However, most of the reported high-performance PSCs are based on the toxic anti-solvents, which is a major issue for the potential commercialization of PSCs. SnO2 has been successfully used as an efficient electron transport layer (ETL) material in PSCs, but the preparation of low-temperature processed crystallization SnO2 ETLs is still a challenge. In this work, ethyl acetate (EA) as a green antisolvent is introduced into the perovskite crystallization process, resulting in uniform and compact perovskite films with large grain size, reduced grain boundaries, and low defect density. Low-temperature (100 °C) processed SnO2 ETL provides good interface contact between ETL and perovskite layer, facilitating photoelectron extraction and transport. As a result, a champion power conversion efficiency (PCE) of 17.83% has been achieved. More importantly, unencapsulated PSC retains 84.80% of its original PCE value after storage in atmosphere for 80 days (>1900 h). Apart from great air stability, the final devices also show excellent thermal (100 °C) stability. It is particularly noteworthy that all the preparation and measurement processes were performed under ambient conditions. These findings present a green path towards manufacturing efficient and stable air-processed PSCs.