Photovoltaic Performance Of Perovskite Solar Cells Research Articles

Side chain modulated ferrocene derivative as the interstitial conductive medium for high-performance and stable perovskite solar cells

The interfacial nonradiative recombination loss caused by the deep traps and mismatched band alignment restrained the commercial viability of perovskite solar cells (PSCs). Herein, we have constructed ferrocene carboxylic acid (FcA) and octafluoropentyl-ferrocenyl-carboxylate (OFFcA) interstitial conductive mediums to modulate the integral heterointerface properties and the photovoltaic performances of PSCs. By comparing the passivation strengths of the two molecules, we found that the synergistic effects among Fc/Fc+ redox shuttle, C=O group, and F substituents realize the optimal elimination of interfacial trap sources. Electron-withdrawing F groups reinforce the capacity of the Fc/Fc+ redox shuttle for the healing of metallic Pb defects and provide extensive anchoring sites to stabilize the organic components. Additionally, the homogeneity of the OFFcA layer as well as the humidity stability of perovskite film are facilitated through the introduction of F substituents, which reduce the contact resistance and improve the interfacial charge transfer. The champion OFFcA-modified device delivers an exceptional PCE of 23.62%, exceeding those of the control (PCE=22.32%) and FcA-modified (PCE=23.06%) devices. Moreover, the unencapsulated OFFcA-modified device retains 82.7% of the primary efficiency at 60% RH for more than 50 d and only loses less than 10% of the primary efficiency when stored in a glove box for more than 2000 h.

Influence of N-type electron acceptors in perovskite absorbers for stabilized perovskite absorbers for high-performance perovskite solar cells

In this study, the impact of n-type organic electron acceptors incorporated in perovskite absorbers via antisolvent-assisted crystallization process is investigated on optical, electrical, and photovoltaic properties of perovskite solar cells (PSCs). The study examines the effect of three representative electron acceptors, including fullerene derivative (PC61BM), non-fullerene acceptor (ITIC), and fluorinated non-fullerene acceptor (ITIC-4F). The findings demonstrate that the inclusion of these electron acceptors stabilizes perovskite absorbers due to strong interaction between the organic acceptors and [PbI6]4- octahedra, leading to the successful passivation of defective antisites. Furthermore, ITIC-4F plays a crucial role in the tailored electronic structure of the perovskite absorber surface, facilitating efficient charge transport and suppressing carrier recombination in the device. The synergetic effect of defect passivation and electrical doping achieved by ITIC-4F resulted in an efficiency improvement of 17.31 % of MAPbI3-based PSCs under 1-Sun illumination, exceeding that of the pristine device (15.62 %) under the same conditions. The device passivated with ITIC-4F also delivered an efficiency of 20.00 % under dim-light irradiation conditions for indoor photovoltaic applications. The results highlight the potential of n-type organic semiconducting molecules as effective additives in the antisolvent-assisted crystallization of perovskite absorbers, offering valuable insights into the design of organic semiconducting additives for improving the film quality of perovskite absorbers and achieving high-performance PSCs. The findings provide a foundation for future research aimed at enhancing the optoelectronic properties and photovoltaic performance of PSCs.

Praseodymium doped nickel oxide as hole-transport layer for efficient planar Perovskite Solar Cells

Hybrid organic/inorganic perovskite solar cells (PSCs) have acquired significant consideration due to high power conversion efficiency (PCE). In PSCs, electron and hole extraction layers have a significant influence on their overall performance. In inverted p-i-n structure-based PSCs, NiOx has been frequently employed as a hole transport layer (HTL) due to its simple processing, wide bandgap, high optical transmittance, excellent chemical stability, and low processing temperature for large-scale fabrication. However, NiOx suffers from low electrical conductivity. Doping of NiOx is an effective technique employed for enhancing electrical as well as optical properties. Herein, the praseodymium doped NiOx (Pr-NiOx) was synthesized by sol-gel method, and films were fabricated to investigate the effect of Pr dopant on the optoelectronic properties and photovoltaic performance of PSCs. Results indicated that Pr doping significantly improved the hole mobility by about threefold and conductivity of NiOx films from 4.68 × 10-6 S cm-1 to 8.27 × 10-6 S cm-1. Moreover, it also enhanced the compactness and interfaces of NiOx HTL. PSCs based on 4 % Pr-doped NiOx HTL- yielded PCE of 9.35 % which is 32.43 % more than the PSCs fabricated using undoped NiOx HTL. The enhanced PCE of PSC devices with Pr-doped NiOx could be attributed to efficient extraction of a hole from an active absorbing layer of perovskite thereby, lowering the probability of unsuitable charge carrier recombination. This work exhibits that Pr-doped NiOx thin film could be a promising alternative material for efficient and stable inverted PSCs.

Elimination of buried interfacial voids for efficient perovskite solar cells

Establishing optimal interfacial contact is crucial for enhancing the efficiency of perovskite solar cells (PSCs). However, formation of voids at buried interface of perovskite films often hinders this critical objective. Our investigation reveals that these buried interfacial voids predominantly manifest at sites characterized by large-angle pits on rough substrate, due to their elevated nucleation barriers compared to their small-angle counterparts. To address this challenge and promote uniform nucleation and growth across all sites, regardless of their angles, we develop an innovative precursor regulation strategy to reduce the nucleation barrier discrepancy between different sites by introducing nonstoichiometric homologous ions or by facilitating the formation of intermediate phases. Notably, the incorporation of FACl additive into the FAPbI3 precursor combines the dual benefits of this approach, yielding high-quality perovskite film with intimate contact and reduced defect density. Consequently, this leads to a significant enhancement in the photovoltaic performance of PSCs.

Effect of the Hammett substituent constant of para-substituted benzoic acid on the perovskite/SnO2 interface passivation in perovskite solar cells.

It is critical to design bifunctional passivation molecules to simultaneously passivate the charge transport layer and perovskite layer at the charge transport layer/perovskite interface in perovskite solar cells (PSCs). In this study, we investigate the effect of para-substituted benzoic acid with different Hammett constants (σ) on the photovoltaic performance of PSCs. Two passivation molecules 4-aminomethylbenzoic acid (4-AMBA) and 4-sulfamoylbenzoic acid (4-SABA) are used to passivate the SnO2 surface with carboxylic acid and the perovskite with para-substituent electron-donating -CH2NH2 (σ = ca. -0.02) and electron-withdrawing -SO2NH2 (σ = ca. +0.60). Compared with non-passivated PSC, the passivation improves the power conversion efficiency (PCE) mainly due to the increased open-circuit voltage (VOC) and fill factor (FF), where the -SO2NH2 substituent is better in improving the photovoltaic performance than the -CH2NH2 one. The trap density is more reduced and the charge extraction ability is more improved by 4-SABA than by 4-AMBA, which indicates that the weak electron-withdrawing nature of a para-substituent such as -SO2NH2 is better for the passivation of the bottom perovskite than a weak electron-donating -CH2NH2 substituent. Consequently, the passivation with 4-SABA enhances the PCE from 22.27% to 23.64%, along with improved long-term stability. This work highlights for the first time the role of the Hammett constant in the surface passivation of PSCs.

Engineering the passivation routes of perovskite films towards high performance solar cells.

Passivation treatment is an effective method to suppress various defects in perovskite solar cells (PSCs), such as cation vacancies, under-coordinated Pb2+ or I-, and Pb-I antisite defects. A thorough understanding of the diversified impacts of different defect passivation methods (DPMs) on the device performance will be beneficial for making wise DPM choices. Herein, we choose a hydrophobic Lewis acid tris(pentafluorophenyl)borane (BCF), which can dissolve in both the perovskite precursor and anti-solvent, as the passivation additive. BCF treatment can immobilize organic cations via forming hydrogen bonds. Three kinds of DPMs based on BCF are applied to modify perovskite films in this work. It is found that the best DPM with BCF dissolved in anti-solvent can not only passivate multiple defects in perovskite, but also inhibit δ phase perovskite and improve the stability of devices. Meanwhile, DPM with BCF dissolved in both the perovskite precursor and anti-solvent can cause cracks and voids in perovskite films and deteriorate device performance, which should be avoided in practical applications. As a result, PSCs based on optimal DPMs of BCF present an increased efficiency of 22.86% with negligible hysteresis as well as improved overall stability. This work indicates that the selection and optimization of DPMs have an equally important influence on the photovoltaic performance of PSCs as the selection of passivation additives.

Post‐Treatment of Metal Halide Perovskites: From Morphology Control, Defect Passivation to Band Alignment and Construction of Heterostructures

AbstractMetal halide perovskite solar cells (PSCs) have witnessed a swift increase in power conversion efficiency in the past decade, emerging as one of the most promising next‐generation photovoltaic technologies for commercialization and low‐carbon energy generation. Through significant efforts in optimizing the processing techniques, high‐quality perovskite thin films can now be prepared with polycrystalline morphologies consisting of monolayer grains. Nevertheless, defects and microstructural disorders still form at the surface/heterointerface and in the bulk of the films. Post‐treatment of the as‐crystallized films has been intensively investigated for passivating these defects, being proved effective for improving the device performance. In this review, the versatile strategies for post‐treating the surface of perovskite thin films toward morphology control, defect passivation, and band alignment are discussed. The tailored surface properties are correlated to charge dynamics at interfaces and photovoltaic performance of PSCs. Since the perovskite heterostructures prepared by simple post‐treatments may suffer from degradation at high temperatures, the recent advances in preparing phase‐pure and stable perovskite heterostructures are also discussed. Finally, a perspective elaborating future opportunities for further enhancing the efficiency and stability of PSCs is provided.

Dual-functional POM@IL complex modulate hole transport layer properties and interfacial charge dynamics for highly efficient and stable perovskite solar cells

The severe interfacial charge recombination as well as the stability issues brought by the Li-TFSI still hinder the commercialization of high-performance perovskite solar cells (PSCs). Here, a polyoxometalates (POMs)-based complex, POM@ ionic liquid (IL), is synthesized and applied as an effective additive that simultaneously enhances the performance and stability of PSCs. The interactions between POM@IL complex and Li-TFSI inhibit the aggregation of Li-TFSI. The synergistic oxidation of POM@IL complex and Li-TFSI towards 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9’-spirobifluorene (Spiro-OMeTAD) effectively enhances the electrical properties of hole transport layer film and the photovoltaic performances of PSCs. The champion device modified with the POM@IL complex yields an excellent power conversion efficiency (PCE) of 22.73%. Moreover, the incorporation of POM@IL improves the humidity stability of PSCs. After storing under high humidity conditions (25 °C, 60% RH) for 1200 h, the POM@IL modified device retained a remarkable 81.2% of its initial PCE. This work provides new insight into constructing POMs-based materials for high-performance photovoltaic devices.

The influence of thickness layers on the efficiency of MAPI solar cells

In this work, a modest method for creating Perovskite solar cells (PSCs) by recycling car batteries is used. Trying to get rid of some structures or materials which are harm to the environment. However, by reusing car batteries we will avoid the disposal of toxic battery materials and provide an alternative technique, readily-available Pb source for fabricating PSCs. Perovskite solar cells (PSCs) were prepared by two-step spin coating solution method on the FTO glass substrate. Lead iodide (PbI2) and methyl-ammonum iodide (CH3NH3I) used to form the structure of the precursor (CH3NH3PbI3). The photovoltaic performance of PSCs and the effect of chemical composition of perovskite layer on performance of PSCs was investigated. Characterization of PSCs by using X-ray diffraction, SEM and the effect of chemical composition on of MAPI films was achieved. It was found that the thickness ratio of (PbI2/MAI) with 3.0:1 have highest fill factor and maximum efficiency.

Investigation the effect of annealing temperature of perovskite layer on performance of perovskite solar cells

The world energy demand is continuously increasing. Due to environment issues, global warming, and other issues, there is a need for clean sources of energy, sustainable energy, i.e. renewable energy technologies. Photovoltaic (PV) technology employing solar energy is regarded as rather most promising and efficient technology among all the renewable energy industries. The further improvement in the efficiency and reliability and also reduction in cost are in great demand, for the healthy development of global economy. Among the third generation solar cells, perovskite cells have attracted a lot of attention due to their high efficiency and low cost construction methods. In this research, low-cost perovskite solar cell (PSC) was prepared, and its photovoltaic performance was investigated. In this project, we tried to get rid of some structures or materials which are harm to the environment. i.e. car batteries. By using lead sheets (from recycled car battery). However, by reusing car batteries we will avoid the disposal of toxic battery materials and provide an alternative, readily-available lead source for fabricating PSC. Perovskite solar cell was prepared by two-steps spin coating solution technique on glass substrates at various thermal annealing deposition temperature. Then photovoltaic performance of PSC was investigated, together with the stability of PSC, and the effect of annealing temperature of perovskite layer on performance of perovskite solar cell. The efficiency of the cell, subjected to thermal annealing at temperature of 100, for 12 minutes was (14.8%). Then the efficiency of the cell altered to (12.4%), after 105 days ageing at room temperature.

Un estudio comparativo de diferentes compuestos de poli(3-hexiltiofeno)-carbono como capas transportadoras de huecos sobre la estabilidad de celdas solares de perovskita preparadas bajo condiciones ambientales

Hole transport layers (HTLs) play an important role in efficiency and stability of perovskite solar cells (PSCs).  Most of the highly efficient PSCs use spiro-OMeTAD doped with Li-TFSI as HTLs, which has to be prepared under inert atmosphere, because the hygroscopic feature of the lithium salt deteriorates the stability of PSCs under ambient conditions. In this work, we report a comparative study of the electrical and morphological properties of different poly(3-hexylthiophene) (P3HT) thin films: pristine, doped with FeCl3, and composites with carbon nanotubes (CNT) or reduced graphene oxide (rGO). Although the electrical conductivity of P3HT films is found to increase with any of those modification methods, the photovoltaic performance of PSCs is highly dependent on the modification agent. P3HT:FeCl3 reduces the photocurrent density of PSCs, while the addition of rGO in P3HT improves charge extraction and stability of PSCs. Furthermore, the insertion of conductive carbon paint between P3HT and the metal contact maintains the original efficiency of non-encapsulated PSCs after continuous illumination for 30 min. It is concluded that carbon modifications in P3HT based HTL can improve the stability of perovskite solar cells totally fabricated under ambient conditions.

Passivation and energy-level change of the SnO2 electron transport layer by reactive titania for perovskite solar cells

Reactive anatase titania (TAc) are incorporated into SnO2 to form a single TAc-SnO2 electron transport layer (ETL) for mixed-cation perovskite solar cells (PSCs). The TAc-SnO2 layer is prepared in a low-temperature process by the advantage of high crystallinity and surface reactivity of TAc. The influence and mechanism of the TAc incorporation on the photovoltaic performance of PSCs are investigated. The TAc-SnO2 ETL presents rapid electron transfer, low trap density, high charge recombination resistance, low hysteresis and good stability. The 2.5-wt% TAc incorporation reveals the highest power conversion efficiency of 20.12 %, a 19 %-fold enhancement compared to the pristine cell with the SnO2 ETL. The enhancement arises from the fact that the TAc can fill up breaching in the pristine SnO2 layer and adjust the ETL energy level. The carboxyl groups of TAc facilitate the formation of solid bonding among SnO2/TAc colloids and prevent ions from accumulation at the interface of ETL/perovskite. The work provides a facile way to fabricate a low-temperature, single-layer and effective ETL for highly efficient PSCs.

Efficient and stable perovskite solar cells by interface engineering at the interface of electron transport layer/perovskite

Perovskite materials owing to their unique properties for photovoltaic applications, widely have been considered by researchers as a desirable candidate for solar cell devices. State-of-the-Art perovskite solar cells (PSCs) recorded a power conversion efficiency (PCE) of 25.7%. Herein, we focused on improving both the stability and photovoltaic performance of PSCs via an interface engineering at the mesoporous titanium dioxide (mp-TiO2)/perovskite interface. We employed 8-Oxychinoline (8-Oxin) material to tailor the surface of mp-TiO2 and prepare a favorable plane for deposition of perovskite. The 8-Oxin material reduced charge transfer resistance (Rct) and increased charge recombination resistance (Rrec) in the PSCs, suggesting an effective defects passivation at the interface of mp-TiO2 and perovskite layers and a reduction in the trap-assisted recombination, which is consistent with the PL results. Our method recorded a champion PCE of 19.03% for PSCs, higher than a PCE of 14.91% obtained for control PSCs. Notably, the 8-Oxin improved the wettability of mp-TiO2 and affected perovskite grain growth, leading to a more compact and smooth perovskite layer. The 8-Oxin material improved the humidity resistance of PSCs due to diminished surface' paths for the reaction with humidity and suppressed surplus PbI2 in the corresponding perovskite layer.

Isomeric Dithienothiophene‐Based Hole Transport Materials: Role of Sulphur Atoms Positions on Photovoltaic Performance of Inverted Perovskite Solar Cells

AbstractHole transport materials (HTMs) are of great significance to improve the efficiency and long‐term stability of perovskite solar cells (PVSCs). Herein, a series of new HTMs based on isomeric dithienothiophene (DTT) are designed and synthesized. Effects of sulphur (S) atoms positions on defect passivation and performance of PVSCs are systematically investigated through theoretical computation, X‐ray diffraction, X‐ray photoelectron spectroscopy, etc. The three molecules display noticeable isomeric effect in energy level, light absorption, and hole mobility. With S atoms varied from bottom‐bottom‐bottom in 3T‐1 to bottom‐bottom‐top in 3T‐2, then to bottom‐top‐bottom in 3T‐3, the grown perovskite crystallite on the corresponding HTMs shows more homeogenous film morphology and less pinhole traps. Meanwhile, nonradiative recombination losses can be suppressed and hole extraction efficiency at HTM/perovskite surface can be improved from 3T‐1 to 3T‐3. As a result, the remarkable improvement of short‐circuit current density nd open‐circuit voltage in inverted perovskite solar cells can be realized with increasing the sulphur atoms contribution to the molecular conjugation. More importantly, 3T‐3‐based dopant‐free HTM achieves a top power conversion efficiency of 19.23% in PVSCs with good device stability under green solvent processing. These results demonstrate the role of S atoms positions in HTMs on photovoltaic performance of PVSCs and the potential of DTT in developing eco‐friendly HTMs toward efficient PVSCs.

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

Impact of Nickel Oxide/Perovskite Interfacial Contact on the Crystallization and Photovoltaic Performance of Perovskite Solar Cells

Spray‐coated nickel oxide (NiOX) is a desirable hole‐transporting material for perovskite solar cells (PSCs) because they are low cost, stable, and readily scalable. Recent research shows that the inferior interface contact of NiOX|perovskite is the main factor that limits the efficiency and stability of the device. Herein, a facile route is introduced to enhance this contact by inserting a tetradecylamine (TeDA) interfacial layer. It is found that TeDA not only can modulate the wettability of NiOX film, thus changing the transformation process of wet film to perovskite, but also can facilitate an efficient charge extraction at this interface. As a result, the efficiency of small‐area (0.16 cm2) solar cells is improved from 15.8% to 18.7%. Moreover, a champion efficiency of 12.9% is achieved for the larger area (53.64 cm2) perovskite solar modules based on spray‐coated NiOX. The optimized devices also show improved stability in comparison with the devices without modification. This work provides a comprehensive understanding of the NiOx|perovskite interface and a new strategy for improving the perovskite quality and photovoltaic performance of PSCs.

Azadipyrromethene Dye-Assisted Defect Passivation for Efficient and Stable Perovskite Solar Cells.

Organic-inorganic perovskite solar cells (PSCs) provide one of the most outstanding photovoltaic (PV) technologies, yet their efficiency, stability, and defect passivation engineering still remain challenging. We demonstrate the use of low-cost, eco-friendly, and multi-functional aza-dipyrromethene (Aza-DIPY) dye molecules to promote the power conversion efficiency (PCE) and the operating stability of PSC devices. The Aza-DIPY dye was meticulously synthesized and incorporated into PSC devices via a one-step solution processing approach. The pyrrole, benzene ring, and chlorine functional groups on the dye have intense interactions with perovskite to passivate surface defects and obtain high-quality perovskite absorbers, resulting in the lengthened carrier recombination time and enhanced fill factor of PSCs. Additionally, the hydrophobic phenyl and halogen functional groups on the Aza-DIPY perform as a protecting barrier against moisture and ameliorate the stability of PSCs. As a consequence, the PV performance of PSCs is considerably improved, with the average PCE increased from 16.71% to 19.71%, and the champion device with Aza-DIPY shows a PCE of 20.46%. The unencapsulated PSC devices with multi-functional molecular Aza-DIPY maintains 89.06% of their beginning PCEs after storage in ambient air (25-30 °C, 50-70% relative humidity) under dark conditions for 100 h, exhibiting a significantly enhanced ambient stability compared with the case of the reference cells without the dye. Furthermore, the Aza-DIPY-modified PSC devices exhibit strong and reversible photoresponses, with a high responsivity of 0.739 mA/W to near-infrared (NIR) laser beams. Our results highlight the potential of synthesizing multi-functional Aza-DIPY dyes-incorporated PSC devices with sensitive NIR/visible light responses, high PV efficiency, and stability.

Improving the Performance of Perovskite Solar Cells with Insulating Additive-Modified Hole Transport Layers.

Invert perovskite solar cells (PSCs) present a great potential for next-generation photovoltaics for their flexibility and tandem adaptability. In order to improve the conductivity of the hole transport layer (HTL), such as poly(triarylamine), highly conductive additives (e.g., F4TCNQ, Li-TFSI) were generally applied to achieve a power conversion efficiency (PCE) exceeding 21%. However, these additives significantly affect the long-term stability of the devices due to their humidity sensitivity. In this work, the HTL was counterintuitively optimized with insulating additives, such as polyphenylene sulfide, which enhanced PCE from 19.1 to 21.5% along with a noticeable improvement in device stability with T50 of 574 h under double 85 aging conditions. The performance enhancement is attributed to larger grain sizes in perovskite films on the HTL and better energy-level alignment between the HTL and perovskite after introducing the insulating additives, which compensate negative influence caused by additive-induced reduction in conductivity. Our work demonstrates that low-conductivity additives, rather than the commonly used high-conductivity counterparts, can also contribute to improving the photovoltaic performance in PSCs.

Sparkling hot spots in perovskite solar cells under reverse bias

• An in-situ temperature and current measurement technique with infrared micro-thermography was developed. • Infrared micro-thermography technique was used to investigate the reverse-bias behavior of perovskite solar cells (PSCs). • The sparkling hot spots were observed in PSCs under reverse bias with abruptly increased current and temperature. • The relationship between the hot spots and the photovoltaic performance of PSCs was revealed. Perovskite solar cells (PSCs) are attracting much attention and are on the way to commercialization. However, some modules are subject to reverse bias in actual fields, so it is meaningful to investigate the reverse-bias behavior of PSCs. Herein, an in-situ temperature and current measurement technique was developed. Intriguingly, some hot spots were observed and then quickly disappeared in the reverse biased PSCs, along with the simultaneous increase in the current and local temperature. Also, the potential mechanism has been revealed and analyzed. An abnormal bulge in the perovskite film was found at the hot spot. Accordingly, the appearance and disappearance of hot spots were perfectly explained by band bending and tunneling current caused by ion accumulation. Additionally, statistical analysis suggested that sparkling hot spots were related to reverse voltage and efficiencies of PSCs. The research provides a great significance for the study of PSCs under reverse bias.

Reformation of thiophene-functionalized phthalocyanine isomers for defect passivation to achieve stable and efficient perovskite solar cells

Lewis acid–base passivation is a significant technique to achieve structural stability of perovskite solar cells (PSCs) by overcoming the issues of wide grain boundaries, crystal defects, and the instability of PSCs. In this work, the combined effects of thiophene with phthalocyanine (Pc) as isomers (S2 and S3) on the photovoltaic performance of PSCs were studied for the first time. Through density functional theory calculations, we confirmed that the position of the S atom in the structure affects Lewis acid–base interactions with under-coordinated Pb2+ sites. The morphology of methylammonium lead iodide (MAPbI3) for passivated devices was improved and thin dense layers with compact surface and large grain size were observed, leading to improvement of the charge extraction ability and reduction of non-radiative recombination and the trap density. A highest power conversion efficiency of 18% was achieved for the Pc S3 passivated device, which was 6.69% more than that of the controlled device. Furthermore, the Pcs passivated devices demonstrated remarkable stability under high-moisture and high-temperature conditions.