Passivation Of Solar Cells Research Articles

Laser induced anti-solvent carbon quantum dots in defect passivation for effective perovskite solar cells

In this study, anti-solvent carbon quantum dots (ASCQDs), generated via pulsed laser irradiation in chlorobenzene (CB), were adopted as an additive for defect passivation of the grain boundaries of CH3NH3PbI3 in hole-conductor-free, carbon-counter-electrode perovskite solar cells (PSCs). The size of the ASCQDs can be easily regulated by different laser fluence. The improvement of perovskite films’ morphology was revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which was beneficial for carrier transport. Higher photoluminescence (PL) intensity as well as prolonged carrier lifetime were proved in the ASCQDs optimized perovskite film, confirmed the laser induced ASCQDs can decrease nonradiative recombination via defect passivation, which can be further verified by the decreased defect density. As a result, the introduction of ASCQDs (1064 nm-50 mJ pulse−1 cm−1-10 min) led to a champion efficiency of 14.95%, which improved 14.04% when compared with pure CB treated PSCs (13.11%). Furthermore, the ASCQDs treated PSCs can still retain 93% and 81% of the initial power conversion efficiency after 600 h in the glovebox and in the atmosphere with humidity of 50–70%, respectively.

A Special Additive Enables All Cations and Anions Passivation for Stable Perovskite Solar Cells with Efficiency over 23%

HighlightsA special additive-(benzylamine)trifluoroboron (BBF) is applied to improve the quality of FAMAPbI3 perovskite.BBF concurrently passivates cationic and anionic perovskite defects.The perovskite solar cell with BBF shows a high power conversion efficiency of 23.24% and an excellent stability.

Analyses and Excess Oxygen Investigations by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy at AlOx/Si Interfaces in Passivated Emitter and Rear Solar Cells

Progressive optimization of the surface passivation of Si solar cells requires access to the elemental composition and chemical bonding characteristics of ultrathin layers and buried interfaces on textured or structured surfaces. The passivation of the rear side of passivated emitter and rear solar cells, for instance, can be realized through AlOx/SiNx stacks, which are known to provide an additional field effect passivation on top of the chemical surface passivation. Herein, transmission electron microscopy is used at locally prepared cross‐sections of such stacks. Electron energy loss spectroscopy is used to extract depth‐resolved information of elemental composition and chemical bonding at nanometer scale. With this, the interfacial excess O fraction, which is crucial for the field effect passivation, is successfully determined for the first time for AlOx passivation layer systems on industrially produced Si solar cells.

Crystal Orientation Modulation and Defect Passivation for Efficient and Stable Methylammonium-Free Dion-Jacobson Quasi-2D Perovskite Solar Cells.

Dion-Jacobson (DJ) quasi-2D perovskite solar cells (PSCs) have received increasing attention due to their greater potentials in realizing efficient and stable quasi-2D PSCs relative to their Ruddlesden-Popper counterpart. The substitution of methylammonium (MA+) with formamidinium is expected to be able to further increase the stability and power conversion efficiency (PCE) of DJ quasi-2D PSCs. Herein, we report a multifunctional additive strategy for preparing high-quality MA-free DJ quasi-2D perovskite films, where 1,1'-carbonyldi(1,2,4-triazole) (CDTA) molecules are incorporated into the perovskite precursor solution. CDTA modification can control phase distribution, enlarge grain size, modulate crystallinity and crystal orientation, and passivate defects. After CDTA modification, more favorable gradient phase distribution and accordingly gradient band alignment are formed, which is conducive to carrier transport and extraction. The improved crystal orientation can facilitate carrier transport and collection. The enlarged grain size and effective defect passivation contribute to reduced defect density. As a result, the CDTA-modified device delivers a PCE of 16.07%, which is one of the highest PCEs ever reported for MA-free DJ quasi-2D PSCs. The unencapsulated device with CDTA maintains 92% of its initial PCE after aging under one sun illumination for 360 h and 86% after aging at 60 °C for 360 h.

Commercial Solar Cells With Graphene Oxide as the Passivation Film

The negative fixed charge density contributed by graphene oxide is estimated as high as 6 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> . Graphene oxide is therefore a promising candidate for Si solar cell passivation. However, the high-temperature steps for manufacturing commercial Si solar cells would change the composition of graphene oxide. Therefore, graphene oxide cannot be directly adopted by commercial PERC manufacturers with the high-temperature firing step after the rear passivation step. To suppress the high-temperature degradation, we have deposited the graphene oxide on the rear surface of commercial IBC cells directly, and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> , J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> and efficiency of the cell all improved after 100 μL graphene oxide deposition. Graphene oxide can be adopted as the passivation material of commercial cells as long as the high-temperature process on graphene oxide can be suppressed.

Laser fabricated carbon quantum dots in anti-solvent for highly efficient carbon-based perovskite solar cells

Additive passivation can be an effective strategy to regulate and control the properties of organic–inorganic halide perovskite film. In this article, carbon quantum dots (CQDs), fabricated by non-focused laser irradiation of carbon nanomaterial diluted in anti-solvent ethyl acetate, denoted as EACQDs, were adopted for perovskite film defect passivation and modification of carbon-based CH3NH3PbI3 perovskite solar cells (PSCs). The size of EACQDs can be tuned by manipulating the laser fluence. The morphology of perovskite film was uncovered through scanning electron microscopy and atomic force microscopy. After embedding of EACQDs, the defect in perovskite crystal was reduced, resulting in the decreased carrier recombination and accelerated carrier transportation, which were demonstrated by electrochemical impedance spectroscopy, photoluminescence and time-resolved photoluminescence. As a consequence, with the optimization of 0.01 mg/mL EACQDs (1064 nm–300 mJ·pulse−1·cm−2–10 min), the power conversion efficiency (PCE) of carbon-based PSCs achieved a maximum value of 16.43%, which improved 23.81% when compared with the pristine PSCs of 13.27%. Furthermore, the EACQDs optimized PSCs also exhibited an excellent stability and still retained 86% of its initial PCE after 50-day storage at the room atmosphere with a humidity of 30–50%.

Thymine as a Biocompatible Surface Passivator for a Highly Efficient and Stable Planar Perovskite Solar Cell

The inevitable defects on the surface of the perovskite layer seriously reduce the efficiency and stability of perovskite solar cells. In this work, thymine, one of the four nucleobases in DNA, is developed as a multifunctional modification agent to passivate the uncoordinated Pb2+ on the perovskite film surface via post-treatment. Spectral data confirm that the surface defects of the perovskite film are effectively passivated via a strong interaction between the Pb ion and carbonyl group. Photoluminescence spectral and electrochemical impedance spectral results demonstrate that the defect-induced recombination of charge carriers at the interface is suppressed. The thymine-modified planar perovskite solar cells exhibit better charge collection, and the fill factor and power conversion efficiency are increased. Moreover, the hydrophobic nature of thymine also significantly improves the humidity stability of the solar cells. The unencapsulated passivated solar cells maintain 68% of the initial efficiency after 1000 h of exposure in the air with a relative humidity of 50 ± 5%. This work provides an effective and eco-friendly surface modification agent for improving the performance of perovskite solar cells.

Naphthylmethylamine post-treatment of MAPbI3 perovskite solar cells with simultaneous defect passivation and stability improvement

The surfaces of perovskite films are vulnerable to the moisture in the surroundings, and surface passivation is a widely accessible technique to solve this problem. Here, we report an effective strategy to improve the stability and photovoltaic performance of MAPbI3 perovskite solar cells by surface passivation with Naphthylmethylamine (NMA). The solar cell devices without NMA showed a highest power conversion efficiency (PCE) of 18.4%, while the devices with NMA achieved a highest PCE of 19.4% under the same conditions. The reduced trap density and enhanced recombination resistance are thought to be the main reasons for the improved photovoltaic performance. Moreover, the long-term stability of the passivated solar cell devices was also greatly enhanced. The NMA-treated device maintained 90% of its original PCE after 90 days storage at a relative humidity of 60% and 25 °C, while the device without NMA only maintained 72% of its original PCE under the same conditions.

Novel cost-effective approach to produce nano-sized contact openings in an aluminum oxide passivation layer up to 30 nm thick for CIGS solar cells

This work presents a novel method of local contact openings formation in an aluminum oxide (Al2O3) rear surface passivation layer by the selenization of the lithium fluoride (LiF) salt on top of the Al2O3 for ultra-thin copper indium gallium (di)selenide (CIGS) solar cells (SCs). This study introduces the potentially cost-effective, fast, industrially viable, and environmentally friendly way to create the nano-sized contact openings with the homogeneous distribution in the thick, i.e. up to 30 nm, Al2O3 passivation layer. The passivation layer is deposited by atomic layer deposition, while the LiF layer is spin-coated. Selenization is done in the H2Se atmosphere and the optimal process parameters are deduced to obtain nano-sized and uniformly allocated openings as confirmed by scanning electron microscopy images. The contact openings were produced in the different thicknesses of the alumina layer from 6 nm to 30 nm. Furthermore, the Al2O3 rear surface passivation layer with the contact openings was implemented into ultra-thin CIGS SC design, and one trial set was produced. We demonstrated that the created openings facilitate the effective current collection through the dielectric Al2O3 layer up to 30 nm thick. However, the upper limit of Al2O3 thickness in which the contact openings can be created by the described method is not established yet. The produced passivated CIGS SCs show increased external quantum efficiency response due to the optical enhancement of the passivated cells. However, the production of SCs on the Al2O3 passivation layer with the openings created by selenization of LiF is not optimized yet.

The effects of pyridine molecules structure on the defects passivation of perovskite solar cells

Pyridine molecules have been widely used to improve the performances of perovskite solar cells (PSCs). However, the effects of pyridine molecular structure, especially the functional group, on the defects passivation of perovskite solar cell have a lack of investigation. In this work, we introduced three pyridine molecules as additives into perovskite layer, including pyridine (PY), 4-methyl-pyridine (MP) and 4-tertbutyl pyridine (TBP), to investigate the influences of the molecular structure on the surface-defect passivation and long-term stability of perovskite solar cells. In fact, the pyridine molecules play two roles in the perovskite films. On the one hand, due to the different molecular structure, these pyridine molecules present differences in electron-pair-donor abilities (TBP > MP > PY), and then affect the interaction of pyridine molecule with Pb2+ in perovskite. Importantly, with the increase of interaction between different functional groups and Pb2+, the defect passivation effect was enhanced. What’s more, the crystal quality and light harvesting ability of the corresponding perovskite layer are improved by large crystal size and slow growth process. Consequently, PSCs with TBP, MP and PY respectively obtained a power conversion efficiency of 17.03%, 15.49% and 14.34%, which are higher than that of without additive (13.34%). On the other hand, owing to the hydrophobicity of groups, the pyridine molecules can enhance the moisture stability of devices. Significantly, the device based on the TBP-modified perovskite film exhibited improved moisture stability among the four type devices, owing to the best characteristic of the tertiary-butyl group with hydrophobicity in TBP.

Simultaneous dual-interface and bulk defect passivation for high-efficiency and stable CsPbI2Br perovskite solar cells

All-inorganic CsPbI2Br is a promising candidate to produce the optimized balance between efficiency and stability. Unfortunately, the CsPbI2Br perovskite films prepared by solution methods often show numerous defects on the grain surfaces and a tendency for phase transition. In this work, we discovered that the proper amount of NiI2 additive enables Ni2+ doping in the perovskite interstitial lattice, while additional Ni2+ ions serve as passivation agents on the grain surfaces; in particular, a profiled distribution appears from the film bulk to both the upper and lower surfaces. The special Ni2+ distribution results in an optimized TiO2 surface for perovskite growth, better perovskite film quality, superior charge extraction capability, and effective suppression of interfacial recombination. As a result, the CsPbI2Br perovskite solar cell (PSC) efficiency is increased to 15.88%, among the highest for its type. Also, the special Ni2+ distribution endows the PSC with improved moisture tolerance. This work provides a promising strategy to overcome the surface/bulk instability issues common in PSCs.

Influence of surface structure on the performance of mono-like Si PERC solar cell

Mono-like Si wafers were textured by both alkaline solution and metal-assisted chemical etching (MACE) process. The influences of surface textures on the diffusion process, surface passivation, electrical property and performance of solar cells were investigated. The results show that the pyramid-like structures obtained by alkaline texturing facilitates a higher surface doping concentration, larger junction depth after diffusion and better passivation effect, compared with the honeycomb-like structures generated by MACE texturing. In the same wafer textured by alkaline solution or MACE, the mono-crystalline region exhibits a higher quantum efficiency than the multi-crystalline region. By combining the MACE and alkaline texturing processes, the honeycomb- and pyramid-like structures were generated on the surface of mono-like Si wafer, resulting in a conversion efficiency of 21.39% that is higher than that of the individually MACE or alkaline-textured solar cells by 0.4% and 0.02%, respectively.

Passivation of InP solar cells using large area hexagonal-BN layers

Surface passivation is crucial for many high-performance solid-state devices, especially solar cells. It has been proposed that 2D hexagonal boron nitride (hBN) films can provide near-ideal passivation due to their wide bandgap, lack of dangling bonds, high dielectric constant, and easy transferability to a range of substrates without disturbing their bulk properties. However, so far, the passivation of hBN has been studied for small areas, mainly because of its small sizes. Here, we report the passivation characteristics of wafer-scale, few monolayers thick, hBN grown by metalorganic chemical vapor deposition. Using a recently reported ITO/i-InP/p+-InP solar cell structure, we show a significant improvement in solar cell performance utilizing a few monolayers of hBN as the passivation layer. Interface defect density (at the hBN/i-InP) calculated using C–V measurement was 2 × 1012 eV−1cm−2 and was found comparable to several previously reported passivation layers. Thus, hBN may, in the future, be a possible candidate to achieve high-quality passivation. hBN-based passivation layers can mainly be useful in cases where the growth of lattice-matched passivation layers is complicated, as in the case of thin-film vapor–liquid–solid and close-spaced vapor transport-based III–V semiconductor growth techniques.

Deep surface passivation for efficient and hydrophobic perovskite solar cells

CF3PEAI, an amphipathic passivation agent, can passivate multiple perovskite defects leading to high performance and stability of perovskite solar cells.

Fluoroarene derivative based passivation of perovskite solar cells exhibiting excellent ambient and thermo-stability achieving efficiency &gt;20%

Trap states in perovskite thin films were passivated effectively by pentafluoroaniline (PFA) additive, thereby significantly enhancing the photovoltaic performances as well as the overall device stability.

Defect passivation and humidity protection for perovskite solar cells enabled by 1-dodecanethiol

The introduction of 1-dodecanethiol surface modifier results in defects repair and enhanced perovskite film stability against high humidity, which positively affect charge transport mechanisms and boost the performance of perovskite solar cells.

Self-assembled carbon dot-wrapped perovskites enable light trapping and defect passivation for efficient and stable perovskite solar cells

A strategy to utilize carbon dots for simultaneously improving photovoltaic performance and longevity of metal halide perovskite solar cells.

D–A–π–A organic sensitizer surface passivation for efficient and stable perovskite solar cells

The more coplanar thiophene π-bridge of MM-4 with richer electron density on the carboxylic acid group passivated defects on the surface and grain boundaries of perovskite films efficiently, and obtained efficient and stable PSCs.

A review of Al2O3 as surface passivation material with relevant process technologies on c-Si solar cell

Surface recombination loss limits the efficiency of crystalline silicon (c-Si) solar cell and effective passivation is inevitable in order to reduce the recombination loss. In this article, we have reviewed the prospects of aluminium oxide (Al2O3) as surface passivation material and associated process technologies are also addressed. Its underlined negative fixed charges, high process stability and process feasibility to use it in ultrathin films, make it exciting one as surface passivation material. Other materials used for passivation and their limitations are addressed. Relevant deposition techniques and their aspects are also discussed here. Ultrathin Al2O3 is generally produced by conventional Atomic Layer Deposition (ALD) methods. But slow deposition rate and low throughput made the ALD process limited its application in commercial solar industry. Plasma Enhanced Chemical Vapour Deposition (PECVD) is also used as alternative one but it suffers from high temperature process stability. Al2O3 deposited by Radio Frequency (RF) sputtering is found out to be one of the best deposition techniques because of its low cost and higher deposition rate.

Synergistic passivation of MAPbI3 perovskite solar cells by compositional engineering using acetamidinium bromide additives

For the global commercialization of highly efficient and stable perovskite solar cells (PSCs), it is necessary to effectively suppress the formation of various defects acting as nonradiative recombination sources in perovskite light-harvesting materials. Interfacial defects between the charge-selective layer and the perovskite are easily formed in the solution process used to fabricate perovskite films. In addition, owing to the difference in thermal expansion coefficients between the substrate and the perovskite film, internal residual tensile stress inevitably occurs, resulting in increased nonradiative recombination. Herein, a simple compositional engineering scheme for realizing efficient and stable PSCs, which incorporates acetamidinium bromide (AABr) as an additive into the MAPbI3 lattice, is proposed. As an additive, AABr has been found to provide synergistic multiple passivation for both internal and interfacial defects. AABr was found to effectively release the tensile strain of the MAPbI3 film by forming a structure stabilized by NH–I hydrogen bonds, as evidenced by calculations based on density functional theory (DFT). Furthermore, the incorporated AABr additives created a charge carrier recombination barrier to enhance charge collection capability by reducing interfacial defects. Accordingly, a power conversion efficiency (PCE) of 20.18% was achieved using a planar device employing AABr-incorporated MAPbI3. This was substantially higher than the 18.32% PCE of a pristine MAPbI3-based device. Notably, unencapsulated PSCs using AABr-incorporated MAPbI3 absorbers exhibited excellent long-term stability, maintaining >95% of initial PCE up to 1200 hours in ambient air.