Air-processed Perovskite Solar Cells Research Articles

Conformal SnO2 and NiOx charge transport layers for pragmatic air-processed perovskite solar cells

The industrialization of perovskite (PVK) solar cells (PSCs) necessitates simple manufacturing, cheapness, nontoxicity, high efficiency, and stability. We report an air-processed lead halide PSCs with cheap, nontoxic, stable NiOx and SnO2 as the hole and electron transport layers separately, to meet all the above commercial requests. By preparing the NiOx (water-dispersible) and SnO2 (oil-dispersible) quantum dots (QDs) with good conductivity and energy band matched well with that of PVK, we fabricate inverted PSCs (ITO/NiOx/PVK/SnO2/Ag) with efficiency up to 20.1/14.6% for active areas of 0.0707/1 cm2, under 1 sun simulated illumination with enhanced UV light ratio. The UV-light resistant PSCs reported here will impel their application in the high altitude areas with strong UV light. Importantly, the monodisperse size and dominant (110) plane of SnO2 QDs achieved by controlling the solvothermal parameters, realize the conformal deposition and defect prevention of SnO2, respectively, thus improving the PSC efficiency and stability.

Ionic liquid regulating perovskite film for air-processed perovskite solar cells

Air-processed perovskite solar cells (PSCs) expediate its commercialization. However, since the intrinsic moisture sensitivity disturb perovskite crystallization and morphology, the photovoltaic performance and shelf stability attenuation are inevitably occurred. Herein, 1-ethy-3-methylimidazolium tetrafluoroborate ([AOEMIM][BF4]) ionic liquids (ILs) was incorporated into perovskite interior to weaken the deleterious influence of ambient moisture on perovskite crystallization. The carboxyl and imidazole from the [AOEMIM]+ moiety passivate undercoordinated Pb2+ defects through coordination bond, while hydrophobic [BF4]- incorporating into the precursor solution protects the films from moisture destruction. Consequently, the targeted PSCs fabricated in open air achieved an impressive PCE of 19.86 % with favorable shelf stability, maintaining 93 % and 89 % of their original efficiencies after 720 h under relative humidity of 80 ± 2 % and after 240 h thermal ageing measurement at 85 °C, respectively.

Sequential spin-coating method in enhancing crystal morphology of ambient air-processed perovskite solar cells

Sequential spin-coating method in enhancing crystal morphology of ambient air-processed perovskite solar cells

Air-Processed All-Inorganic Halide Perovskites Integrated Photorechargeable Supercapacitors.

Due to their easy integration for self-powered operation, integrated energy harvesting and storage could be the game changer in smart, flexible, and portable electronic devices. Three-electrode integration is the most promising approach among all possible configurations because it is less complex and compatible with most techniques. Although the photoconversion efficiency has increased above 20% due to the integration of high-performance perovskite solar cells, the electrochemical storage efficiency (efficacy of the integration) is much below 80% due to a significant potential drop and impedance mismatch. In this context, we introduced perovskite-based solid-state thin film supercapacitors integrated with stable, air-processed perovskite solar cells for an uninterrupted power supply. Our measurement shows that the best performance can be achieved by optimizing several parameters, including series-connected solar cells, light intensity, and photovoltaic active area. The critical challenge with these integrated systems is to maintain a uniform charging current of the supercapacitors throughout the charging cycle while minimizing self-discharging. We achieved an electrochemical storage efficiency of ∼87% at an overpotential of 0.8 V. The overpotential can be as low as 2 mV. We fabricated fully solution-processed series-connected solar cells to integrate with stacked supercapacitors to improve the operating voltage beyond 2.1 V. The photocharging and dark discharging of these integrated devices have been tested over 200 cycles, and a negligible drop in efficiency has been observed. Our detailed energy conversion and storage analysis in these systems unveils the mechanism and losses due to three-terminal integration.

Efficient Air-Processed MA-Free Perovskite Solar Cells by SH-Based Silane Interface Modification.

Air-processed perovskite solar cells (PSCs) with high photoelectric conversion efficiency (PCE) can not only further reduce the production cost but also promote its industrialization. During the preparation of the PSCs in ambient air, the contact of the buried interface not only affects the crystallization of the perovskite film but also affects the interface carrier transport, which is directly related to the performance of the device. Here, we optimize the buried interface by introducing 3-mercaptopropyltrimethoxysilane (MPTMS, (CH3O)3Si(CH2)3SH) on the nickel oxide (NiOx) surface. The crystallization of the perovskite film is improved by enhancing surface hydrophobicity; besides, the SH-based functional group of MPTMS passivates the uncoordinated lead at the interface, which effectively reduces the defects at the bottom interface of perovskite and inhibits the nonradiative recombination at the interface. Moreover, the energy level between the NiOx layer and the perovskite layer is better matched. Based on multiple functions of MPTMS modification, the open circuit voltage of the device is obviously improved, and efficient air-processed methylamine-free (MA-free) PSCs are realized with PCE reaching 21.0%. The device still maintains the initial PCE of 85% after 1000 h aging in the glovebox. This work highlights interface modification in air-processed MA-free PSCs to promote the industrialization of PSCs.

Air-Processed Perovskite Solar Cells with >25% Efficiency and High Stability Enabled by Crystallization Modulation and Holistic Passivation.

Organic semiconductors (e.g., PCBM and IDIC) frequently serve as interface passivants for perovskite solar cells (PSCs) due to their beneficial passivation effects on perovskite interfaces. However, their passivation to the interiors of perovskite films is greatly limited by their poor solubility in polar solvents and compatibility issues. Here the facile synthesis of organic semiconductor nanoparticle (NP) passivants that readily disperse in perovskite inks is reported. Adding these NPs into perovskite inks not only modulates perovskite crystallization, improves film quality and conductivity, but also achieves holistic bulk film passivation. Consequently, blade-coated p-i-n PSCs with ICBA NPs achieve an impressive efficiency of 25.1% (independently certified as 25.0%), the highest reported value for air-processed PSCs irrespective of fabrication methods or device structures. This work develops a novel approach for effective and holistic perovskite passivation by converting conventional passivants to perovskite-compatible NPs, paving the way for more efficient and stable perovskite solar devices.

Bifunctional chemical bonds for trap inactivation and ion immobilization in fully ambient-air processed perovskite solar cells

For the past few years, air-processed perovskite solar cells (PSCs) have raised interests from researchers around the world, due to the urgent demand for the roll-to-roll (R2R) industrialization. However, lots of detrimental effects, such as imperfect active film quality and plentiful traps on the surface, or especially grain boundaries (GBs) for the samples fabricated under the ambient conditions, can seriously damage both the performance and stability of PSCs. Thereby, in this study, a cross-linking passivator, dodecanoic acid (DA), was incorporated in order to improve the crystallinity of air-processed perovskite films. On the one hand, DA agents with carboxy group and –O points, could chelate tightly with nonbonding Pb2+ ions of perovskite crystal, as well as interact with I− anions through hydrogen network. The hindered trap formation and immobilized ions improve the power conversion efficiency (PCE) of the device. On the other hand, the long hydrophobic alkyl chains of DA were prone to be accumulated at the GBs of the perovskite grains, thus boosting the moist resistance. Consequently, the champion device gained a PCE of 20.23% with hindered hysteresis. Moreover, the unpackaged DA-passivated PSC retains 81.7% of its original PCE after aging under ambient conditions for 5 weeks. This simple and viable approach for fabricating perovskite-based optoelectronic device with high performance and promising stability, can promote its large production and commercialization.

Synchronous Regulation Strategy of Pyrrolidinium Thiocyanate Enables Efficient Perovskite Solar Cells and Self-Powered Photodetectors.

Developing inventive approaches tocontrol crystallization and suppress trap defects in perovskite films is crucial for achieving efficient perovskite photovoltaics. Here, a synchronous regulation strategy is developed that involves the infusion of a zwitterionic ionic liquid additive, pyrrolidinium thiocyanate (PySCN), into the perovskite precursor to optimize the subsequent crystallization and defects. PySCN modification not only orchestrates the crystallization process but also deftly addresses trap defects in perovskite films. Within this, SCN- compensates for positively charged defects, while Py+ plays the role of passivating negatively charged defects. Based on the vacuum flash evaporation without anti-solvent, the air-processed perovskite solar cells (PSCs) with PySCN modification can achieve an extraordinary champion efficiency of 22.46% (0.1 cm2) and 21.15% (1.0 cm2) with exceptional stability surpassing 1200 h. Further, the self-powered photodetector goes above and beyond, showcasing an ultra-low dark current of 2.13 × 10-10 A·cm-2, a specific detection rate of 6.12×1013Jones, and an expansive linear dynamic range reaching an astonishing 122.49dB. PySCN modification not only signifies high efficiency but also ushers in a new era for crystallization regulation, promising a transformative impact on the optoelectronic performance of perovskite-based devices.

Rapid Surface Reconstruction in Air-Processed Perovskite Solar Cells by Blade Coating.

Blade coating has been developed to be an essential technique for large-area fabrication of perovskite solar cells (PSCs). However, effective surface treatment of the perovskite layer, which is a critical step for improving PSC performance, remains challenges during blade coating due to the short interaction time between the modification solution and the perovskite layer, as well as the limited selection of available organic solvents. In this study, a novel modifier N,N-diphenylguanidine monohydrobromide (DPGABr) dissolved in acetonitrile (ACN) is blade coated on the MA0.7 FA0.3 PbI3 surface in air to reconstruct the perovskite surface in hundreds of milliseconds. This work finds that the solvent ACN rapidly dissolves organic iodide of the perovskite layer and leads to a PbI2 -rich surface, providing reactive sites for DPGABr to form a thin DPGABr/PbI2 complex layer. This surface reconstruction can effectively passivate defects and induce n-type doping on the perovskite surface to facilitate electron transfer. The resultant devices show a 15% improvement in average power conversion efficiency. More importantly, the devices with the surface reconstruction show outstanding long-term stability, with negligible performance degradation even after 1-year storage in air. This study presents a convenient and effective approach for improving the performance of blade-coated PSCs prepared in air.

Ionic surfactants of different dipole moments as anti-solvent additives for air-processing MAPbI3−xClx perovskite thin films

Three ionic surfactants, didodecyldimethylammonium bromide (DDABr), sodium lauryl ether sulfate (NaLES) and sodium lauryl sulfate (NaLS), with different dipole moment values: 0.907, 17 and 212 Debye, respectively, have been used as anti-solvent additives to remove the moisture from perovskite precursor solutions. The three additives impact in different ways on the crystallinity, wettability and morphology of perovskite thin films, as well as on the stability and efficiency of air-processed perovskite solar cells (PSCs). The hydrophobic groups of the additives at the surface of perovskite thin films help to increase the stability of PSCs, especially DDABr of the lowest dipole moment. On the other hand, NaLES, of the highest dipole moment, is the most efficient to extract moisture from the perovskite precursor coatings, increasing the average power conversion efficiency (PCE) of NaLES-based PSCs from 16.16 ± 0.94% to 17.21 ± 0.32% in comparison with that of the reference. Furthermore, the synergy between NaLES and the perovskite precursor additive, KI, achieves the best photovoltaic performance of the PSCs, leading to an average PCE of 17.42% and the best PCE of 18.75%. It is concluded that ionic surfactants of different dipole moments are good candidates as anti-solvent additives to improve the efficiency and stability of air-processed PSCs.

Improved Performance of Air-Processed Perovskite Solar Cells via the Combination of Chlorine Precursors and Potassium Thiocyanate.

Due to their low cost and high efficiency, hybrid perovskite solar cells (PSCs) have shown the most outstanding competitiveness among third-generation photovoltaic (PV) devices. However, several challenges remain unresolved, among which the limited stability is arguably the main. Chlorine (Cl) has been widely employed to yield PV performances, but the Cl-doping mechanism and its role in mixed-halide PSCs are not entirely understood. Here, we investigate the effect of Cl-doping using different precursors such as formamidinium chloride (FACl), cesium chloride (CsCl), and lead chloride (PbCl2), which lead to the incorporation of Cl at different sites of the perovskite crystal. We demonstrate that the stability and efficiency of air-processed PSCs are strongly affected by Cl bonding into the cationic chloride precursor. Furthermore, adding potassium thiocyanate (KSCN) leads to the maximum efficiency of 18.1%, improving the operational stability with only 18% PCE loss after 520 h, stored under ambient conditions. Incorporating CsCl and KSCN presents an effective approach to further boost the performance and thermal stability of PSCs by tailoring the composition of the perovskite's composition. Finally, we used the slot-die method to demonstrate that our strategy is scalable for large-area devices that have shown similar performance. Our results show that fully air-processed and stable PSCs with high efficiency for large production and commercialization are achievable.

Deep and shallow level defect passivation via fluoromethyl phosphonate for high performance air-processed perovskite solar cells

Air-processed perovskite solar cells (PSCs) with high performance are considered to be the inevitable trend of low-cost commercial manufacturing. Nevertheless, the deep- and shallow-level defects of humid-air-processed perovskite films are the main sources of photoelectric conversion efficiency (PCE) deficit. Herein, a difluoromethyl phosphonic acid diethyl ester (2F-PAE) with tri-chelation sites is implanted into perovskite absorber to passivate uncoordinated Pb2+/Pb clusters and raise formation energies of vacancies in perovskite films. The P = O/C-O groups in 2F-PAE offer tri-chelation sites to bind tightly with uncoordinated Pb2+/Pb clusters, which passivates deep-level defects and regulates perovskite crystallization. -CF2 groups in 2F-PAE generate electrostatic interaction with FA+, which helps to passivate shallow-level defects. The formation energies of Pb, I and FA vacancies can be increased by more than twice under the synergistic passivation of P = O, C-O and -CF2. Thus, the open-circuit voltage (VOC) of the humid-air-processed PSCs with 2F-PAE increases to 1.188 V. 2F-PAE passivated PSCs dramatically improve the PCE from 20.54 % to 23.69 %. PSCs using 2F-PAE display excellent moisture and thermal stability, retaining 82 % of its initial efficiency after 1500 h under continuous illumination, while the control PSCs maintain only 44 %. This strategy offers crucial insights for selecting multifunctional molecules to boost the performance of PSCs.

Hydrogen Bond Network for Efficient and Stable Fully Ambient Air-Processed Perovskite Solar Cells with Over 21% Efficiency

Hydrogen Bond Network for Efficient and Stable Fully Ambient Air-Processed Perovskite Solar Cells with Over 21% Efficiency

Controlled crystallization and surface engineering of mixed-halide γ-CsPbI2Br inorganic perovskites via guanidinium iodide additive in air-processed perovskite solar cells

In this report, we demonstrate enlarged grain size (up to ∼3 μm) in ambient-stable black γ-phase CsPbI2Br thin films through the regulated addition of guanidinium iodide (GAI) as an effective volatile additive. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) measurements indicate the complete sublimation of GAI following annealing, with no inclusion inside the final γ-CsPbI2Br perovskite lattice. GAI is found to participate by retarding the cation–anion reaction via the Cs+ and GA+ cation-exchange process. We find that inorganic perovskite solar cells (IPSCs) devices made from (CsPbI2Br)0.925 + 0.075 GAI and a phenyltrimethylammonium chloride (PTACl) passivation retain a solar-friendly band-gap of 1.91 eV and excellent device performance, with the best open-circuit voltage reaching as high as 1.34 V, with highly reproducible and stable photo conversion efficiencies of 16.88% (for 0.09 cm2) and 15.60% (large area 1 cm2) under ambient conditions. Photostability analysis further demonstrated negligible efficiency loss over 1000 h under continuous one-sun equivalent illumination, indicating GAI additive as a promising approach toward ambient stable, all-inorganic high-efficiency solar cells.

Surface-bulk-passivated perovskite films via 2-thiophenemethylammonium bromide and PbBr2 for air-processed perovskite solar cells with high-stability

Suppressing non-radiative recombination induced by defect is of much concern to efficient and stable perovskite solar cells (PSCs). We report a cooperative strategy to passivate both interfacial and bulk defects in perovskite layer by coupling interface engineering and additive engineering. 2-Thiophenemethylammonium bromide (2-ThMAB) is synthesized by recrystallization. PbBr2 used as an additive is introduced into the perovskite precursor solution. 2-ThMAB features with an electron-rich π-system and 2-thiophene group. Br− ions have an impact on perovskite lattice reorganization. The synergistic modification of 2-ThMAB and PbBr2 enables the external electronic state modulation and internal bandgap adjustment of perovskite, which is beneficial to passivate defect and inhibit ion migration. As a result, a modified PSC exhibits a high-power conversion efficiency of 20.01% with negligible hysteresis for an all-air-processed device. More importantly, a non-encapsulated device exhibits excellent long-term stability of T98 of > 720 h. This study thus provides a new way to obtain highly stable all-air-processed PSCs..

Design, synthesis, optical studies, and application of all-inorganic layered double perovskites as stabilizers in ambient air processed perovskite solar cells

Five all-inorganic layered double perovskites including Cs4CuCr2Cl12, Cs4CuCo2Cl12, Cs4CuSb2Cl12, Cs4CuLa2Cl12, and Cs4CuCe2Cl12 were synthesized and their properties were investigated. Cs4CuSb2Cl12 with a suitable band gap near 1 eV, a truncated hexagonal trapezohedron morphology and large grains (5 µm) was added as the most favorable additive into CH3NH3PbI3 perovskite of ambient air processed perovskite solar cells (PSCs). The CH3NH3PbI3 films containing 1, 3, and 5% w/w of Cs4CuSb2Cl12 were studied. The PSC fabricated using the perovskite film containing 1% Cs4CuSb2Cl12 exhibited an increase of 20.32% in power conversion efficiency (PCE) compared with the device without the additive (from 5.66 to 6.81%). The Cs4CuSb2Cl12 additive significantly ameliorated the PSCs stability. These improvements were attributed to the large grain size, high electron-hole recombination resistance, low direct and indirect bandgaps (1.16 and 1.10 eV), strong light absorption, defects passivation, and structural stability of Cs4CuSb2Cl12 confirming this material is an effective candidate for PSCs fabrication.

High efficiency stable planar perovskite solar cells via heavy water additive

Although great advances have been made in low-cost manufacturing of air-processed perovskite solar cells (PSCs), the moisture degradation of halide perovskite films remains a key problem to be urgently solved. High-quality perovskite films with large grains and uniform coverage are essential to enhance the performance of PSCs with high efficiency and moisture stability. Herein, heavy water (D2O) is employed as an additive in PbI2 precursor to manipulate the average grain size and enhance surface coverage of perovskite film, resulting in improved humidity stability of PSCs under ambient conditions. It is found that the introduction of D2O effectively improves the quality of perovskite film and significantly reduces the grain boundaries for reduced carrier recombination. The optimal concentration of D2O can boost the in-plane growth of perovskite films and increase the average grain size of perovskite from 494 nm to 717 nm. Consequently, the PSCs based on the perovskite film with 1% D2O exhibits a superior PCE of 21.66% (0.055 cm2) in small area, which is 9.78% higher than that of the control device (19.73%). In addition, the large-area (1 cm2) PSCs with 1% D2O show an efficiency of 20.02%. The unencapsulated PSCs made with 1% D2O can remain 95% of its initial PCE after aging 60 days in ambient air under dark with 20–25% relative humidity.

A facile strategy for high performance air-processed perovskite solar cells with dopant-free poly(3-hexylthiophene) hole transporter

Poly(3-hexylthiophene) (P3HT) based devices possess potential toward low-cost and easy fabrication for high-performance perovskite solar cells (PSCs). However, these devices currently suffer from stability and relative low performance. Herein, a gradient mixed-cation perovskite is obtained by a facile strategy of tailoring MAPbI3-xClx, in which MAFAPbI3-xClx were constructed in ambient air by directly spin-coating FAI onto perovskite intermediate phase. The pristine device shows an inferior power conversion efficiency (PCE) of 13.71%, whereas the as-optimized device achieves a PCE of 16.26%. A gradient distribution of FA cation is revealed by crystal unit parameters and energy dispersive spectrometer (EDS). The lifted valence band edge matches better with the HOMO of P3HT, thus resulting in the faster charge extraction. In addition, the reduced trap states lead to the enhanced crystallinity and the mitigation of perovskite/P3HT interface, and then the stability is significantly enhanced. Our work provides a facile way to improve the performance of P3HT based air-processed PSCs, which can bring these devices closer to low-cost commercial applications.

Multi-functional cyclic ammonium chloride additive for efficient and stable air-processed perovskite solar cells

Because morphology and defect of organic-inorganic halide perovskite film is very sensitive to moisture and oxygen, it is important to develop humidity tolerant air-processes that produce high quality film with minimal defects for the successful commercialization of perovskite solar cells (PeSCs). As an attempt to optimize perovskite film in the air, we develop a cyclic quaternary ammonium chloride (N-(2-hydroxyethyl)-N-methylpyrrolidinium chloride, M-P chloride) with a pentagonal ring and hydroxyl functional group as an effective additive. The Cl− anions in M-P chloride increase the crystallinity and the grain size by retarding nucleation and growth rate. After crystal growth, bulky M-P chloride diffuses out and remains on the grain boundaries and surface of the perovskite, and thus passivates both types of defects. Furthermore, since the M-P chloride may act as a moisture absorber, the intermediate phase of the perovskite can be protected from the moisture. As a result, this strategy can not only modulate the crystallinity and film morphology but also passivate the defects, leading to enhanced efficiency and stability, regardless of humidity. In particular, even at high humidity of ∼77%, PeSC with M-P chloride exhibits 18.20% power conversion efficiency (PCE) without any hysteresis behavior.

Optimization of TiO2 paste concentration employed as electron transport layers in fully ambient air processed perovskite solar cells with a low-cost architecture

The optimization of thickness and surface roughness of the TiO 2 layer as an efficient electron transporting layer (ETL) plays a significant role on the performance improvement of perovskite solar cells (PSCs). In the present investigation, TiO 2 pastes synthesized with various concentrations under hydrothermal conditions were utilized to deposit the TiO 2 films of tunable porosities as the ETLs of PSCs. Also, the PSCs were fabricated with a structure of FTO/block-TiO 2 (b-TiO 2 )/m-TiO 2 /CH 3 NH 3 PbI 3 (MAPbI 3 )/CuInS 2 (CIS)/carbon as a low-cost architecture. Moreover, the effect of the TiO 2 paste concentration was studied on the performances of PSCs under fully ambient conditions. The optimal TiO 2 layer was constructed with 20 wt% TiO 2 paste concentration, which resulted in the formation of a hole‐free, smooth, and compact ETL layer. The champion perovskite solar cell fabricated with the 20 wt% TiO 2 paste concentration showed the highest power conversion efficiency (PCE) of 13.09% (J SC = 20.80 mA cm −2 , V OC = 0.98 V and FF = 0.64) but the champion PSC device made with the 10 wt% TiO 2 paste exhibited the lowest PCE = 8.05% (J SC = 19.83 mA cm −2 , V OC = 0.91 V and FF = 0.45). These results illustrated that the optimal 20 wt% TiO 2 paste caused ∼163% enhancement in the PCE of the device. Consequently, it could be suggested for application in fabrication of cost-effective and large scale PSCs. • Perovskite solar cells (PSCs) were fabricated by TiO 2 pastes of diverse concentrations. • Surface roughness and thickness of the TiO 2 electron transporting layers were optimized. • The optimal concentration of the mesoporous TiO 2 film was 20 wt%. • The highest efficiency (13.09%) was measured for the cell containing 20 wt% TiO 2 . • The champion device displayed FF = 0.64, J SC = 20.80 mA cm −2 and V OC = 0.98 V.