Inverted Perovskite Solar Cells Research Articles

Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution-Processed and Structurally Ordered Fullerene.

The electron transporting layer (ETL) used in high performance inverted perovskite solar cells (PSCs) is typically composed of C60, which requires time-consuming and costly thermal evaporation deposition, posing a significant challenge for large-scale production. To address this challenge, herein, we present a novel design of solution-processible electron transporting material (ETM) by grafting a non-fullerene acceptor fragment onto C60. The synthesized BTPC60 exhibits an exceptional solution processability and well-organized molecular stacking pattern, enabling the formation of uniform and structurally ordered film with high electron mobility. When applied as ETL in inverted PSCs, BTPC60 not only exhibits excellent interfacial contact with the perovskite layer, resulting in enhanced electron extraction and transfer efficiency, but also effectively passivates the interfacial defects to suppress non-radiative recombination. Resultant BTPC60-based inverted PSCs deliver an impressive power conversion efficiency (PCE) of 25.3% and retain almost 90% of the initial values after aging at 85°C for 1500 hours in N2. More encouragingly, the solution-processed BTPC60 ETL demonstrates remarkable film thickness tolerance, and enables a high PCE up to 24.8% with the ETL thickness of 200 nm. Our results highlight BTPC60 as a promising solution-processed fullerene-based ETM, opening an avenue for improving the scalability of efficient and stable inverted PSCs.

Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution‐Processed and Structurally Ordered Fullerene

Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution‐Processed and Structurally Ordered Fullerene

Enhancing photovoltaic performance and stability of inverted perovskite solar cells via multifunctional molecular additive

The film quality of perovskite absorber plays a fundamental role in determining the efficiency and stability of perovskite solar cells (PSCs), of which high crystallinity and low defect density are consistently persuaded. Here, a strategy using multifunctional additive of N,N’-Diallyl-L-tartardiamide (NDT) to produce high-quality perovskite film is proposed. The rich coordination and hydrogen bonding between NDT and perovskite effectively passivate trap states, improve film crystallinity, stabilize perovskite crystal structure and confine ions migration, resulting in enhancement of charge transport and suppression of nonradiative recombination. Consequently, compared with the control device (19.07%), the NDT-modified devices achieve a champion efficiency of 21.71% with negligible hysteresis as well as excellent air and light stability. This work presents a facile and effective approach via multifunctional molecular additive to achieve high-performance inverted (p-i-n) PSCs.

Enhancement the performance of MAPbI3 perovskite solar cells via germanium sulfide doping

In this study, we successfully doped Germanium sulfide (GeS) particles in methylammonium lead triiodide (CH3NH3PbI3) films to create highly efficient inverted perovskite solar cells (PSC). Various characterization methodologies were employed to examine the impact of GeS on the morphological, structural, and compositional properties of the CH3NH3PbI3 perovskite. The X-ray diffraction and Raman spectroscopy analyses of the synthesized products demonstrated that the crystallinity was enhanced, and tetragonal perovskite structures were generated without any impurities when GeS was used at a high concentration. The surface morphology results indicated that the CH3NH3PbI3 perovskite possessed thin coatings with compact, uniform, and smooth surfaces, with large grain size. The production of a high-quality CH3NH3PbI3 film from the CH3NH3PbI3: GeS phase results in improved carrier lifetime, decreased charge-trap density, and nonradiative recombination of the perovskite films. Band gap was observed to be correlated with grain size and crystallinity, which was accompanied by an increase in GeS concentration. We attained a maximum conversion efficiency of 17.46 % by fabricating solar cells with the following structure: soda-lime glass FTO/TiO2/CH3NH3PbI3: GeS/spiro-oMeTAD/Au. Based on our findings, we believe that the doping of GeS is a promising method for improving the properties of perovskite solar cells that are based on CH3NH3PbI3 thin films.

Magnetron sputtered nickel oxide with suppressed interfacial defect states for efficient inverted perovskite solar cells

Widely used spin-coated nickle oxide (NiOx) based perovskite solar cells often suffer from severe interfacial reactions between the NiOx and adjacent perovskite layers due to surface defect states, which inherently impair device performance in a long-term view, even with surface molecule passivation. In this study, we developed high-quality magnetron-sputtered NiOx thin films through detailed process optimization, and compared systematically sputtered and spin-coated NiOx thin film surfaces from materials to devices. These sputtered NiOx films exhibit improved crystallinity, smoother surfaces, and significantly reduced Ni3+ or Ni vacancies compared to their spin-coated counterparts. Consequently, the interface between the perovskite and sputtered NiOx film shows a substantially reduced density of defect states. Perovskite solar cells (PSCs) fabricated with our optimally sputtered NiOx films achieved a high power conversion efficiency (PCE) of up to 19.93% and demonstrated enhanced stability, maintaining 86.2% efficiency during 500 h of maximum power point tracking under one standard sun illumination. Moreover, with the surface modification using (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid (DMAcPA), the device PCE was further promoted to 23.07%, which is the highest value reported for sputtered NiOx based PSCs so far.

The Promise and Challenges of Inverted Perovskite Solar Cells.

Recently, there has been an extensive focus on inverted perovskite solar cells (PSCs) with a p-i-n architecture due to their attractive advantages, such as exceptional stability, high efficiency, low cost, low-temperature processing, and compatibility with tandem architectures, leading to a surge in their development. Single-junction and perovskite-silicon tandem solar cells (TSCs) with an inverted architecture have achieved certified PCEs of 26.15% and 33.9% respectively, showing great promise for commercial applications. To expedite real-world applications, it is crucial to investigate the key challenges for further performance enhancement. We first introduce representative methods, such as composition engineering, additive engineering, solvent engineering, processing engineering, innovation of charge transporting layers, and interface engineering, for fabricating high-efficiency and stable inverted PSCs. We then delve into the reasons behind the excellent stability of inverted PSCs. Subsequently, we review recent advances in TSCs with inverted PSCs, including perovskite-Si TSCs, all-perovskite TSCs, and perovskite-organic TSCs. To achieve final commercial deployment, we present efforts related to scaling up, harvesting indoor light, economic assessment, and reducing environmental impacts. Lastly, we discuss the potential and challenges of inverted PSCs in the future.

Interfacial crosslinking benzimidazolium enables eco-friendly inverted perovskite solar cells and modules

Interfacial engineering via controlled crosslinking at perovskite surface is of significance to address the interfacial loss in inverted perovskite solar cells (PSCs), while is unfortunately impeded by the unsatisfied interfacial charge extraction and transfer owing to the inherent low conductivity of the formed crosslinked network. We herein propose and validate a strategy of interfacial crosslinking benzimidazolium (ICB) that is capable of reducing the surface residual strain of perovskite and improving the interfacial carrier transfer, leading to a new benchmark of power conversion efficiency (PCE) up to 25.30 % in inverted PSCs, as well as 21.73 % in inverted PSC modules (6 × 6 cm²). Such the ICB network also results in sustainable PSCs and modules with superior stability even under various harsh conditions, e.g. suppressing lead leakage of PSCs with the rate of 83.6 %, maintaining the initial efficiency of 90 % after 1200 h of continuous heating at 85 °C, and 92.8 % of its pristine efficiency over 1200 h of continuous irradiation. We thus believe that present work demonstrates the potential of ionic molecules crosslinking at interfaces for high performance inverted PSCs.

Enhancing Hole Transport Uniformity for Efficient Inverted Perovskite Solar Cells through Optimizing Buried Interface Contacts and Suppressing Interface Recombination

[4‐(3,6‐dimethyl‐9H‐carbazol‐9yl)butyl]phosphonic acid (Me‐4PACz) self‐assembly material has been recognized as a highly effective approach for mitigating nickel oxide (NiOx) surface‐related challenges in inverted perovskite solar cells (IPSCs). However, its uneven film generation and failure to effectively passivate the buried interface defects limit the device's performance improvement potential. Herein, p‐xylylenediphosphonic acid (p‐XPA) containing bilateral phosphate groups (‐PO3H2) is introduced as an interface layer between the NiOx/Me‐4PACz and the perovskite layer. P‐XPA can flatten the surface of hole transport layer and optimize interface contact. Meanwhile, p‐XPA achieves better energy level alignment and promotes interfacial hole transport. In addition, the bilateral ‐PO3H2 of p‐XPA can chelate with Pb2+ and form hydrogen bond with FA+ (formamidinium cation), thereby suppressing buried interface non‐radiative recombination loss. Consequently, the IPSC with p‐XPA buried interface modification achieves champion power conversion efficiency of 25.87% (certified at 25.45%) at laboratory scale (0.0448 cm2). The encapsulated target device exhibits better operational stability. Even after 1100 hours of maximum power point tracking at 50 ℃, its efficiency remains at an impressive 82.7% of the initial efficiency. Molecules featuring bilateral passivation groups optimize interfacial contact and inhibit interfacial recombination, providing an effective approach to enhancing the stability and efficiency of devices.

Small molecule induced interfacial defect healing to construct inverted perovskite solar cells with high fill factor and stability

Chemical defects at the surface and grain boundaries of perovskite crystals cause deterioration of conversion efficiency and stability of perovskite solar cells (PSCs). In this study, a multifunctional additive, 5-fluoro-2-pyrimidine carbonitrile (FPDCN) molecule, is added into the perovskite precursor solution in order to passivate the uncoordinated Pb2+ by the cyanogen (–CN) group and pyrimidine N in FPDCN. Interestingly, fluorine (F) atoms interact with FA+ to form hydrogen bonds, which could regulate the perovskite crystallization process for the formation of high-quality perovskite crystals. Besides, the F atoms in FPDCN increase the water contact angle of perovskite films. As a result, the carrier extraction and transport in the perovskite film are significantly enhanced, and the non-radiative recombination is suppressed. The corresponding devices achieve a champion photovoltaic conversion efficiency (PCE) of 20.7 % and a fill factor (FF) of over 83 %. The device based on FPDCN shows long-term stability under a high-humidity atmospheric environment by maintaining 85 % of the initial efficiency after aging of 700 h in the glove box. This study provides a simple and convenient method to prepare stable and efficient PSCs by optimizing the perovskite precursor solution.

Synthesis of tungsten-doped zinc oxide nanoparticles using Aloe vera extracts for perovskite solar cells

A green, plant extract-mediated synthesis technique utilizing the Aloe vera stem extract with Zinc acetate (Zn(CH₃CO₂)₂·2H₂O), and Tungsten chloride (WCl2) salt has been employed to grow Zinc Oxide (ZnO) and tungsten doped ZnO (W-ZnO) nanoparticles (NPs). The formation of NPs was confirmed by FESEM with EDX and TEM analysis. The synthesized NPs have been employed for fabricating ZnO and W-ZnO thin films and the electro-optical properties of the films have also been investigated in detail. The thin films have obtained via spin coating and followed by annealing at 350 °C for 3 h in an ambiance atmosphere. The films showed smooth surfaces with a bandgap of 3.20 and 3.25 eV for ZnO and W-ZnO respectively. Finally, a novel structure inverted perovskite solar cells (PSCs) has been numerically analyzed utilizing the films as an electron transporting layer (ETL) for realizing the device performance. The highest PCE of the device for synthesized ZnO and W-ZnO has been found to be 21.16 % and 23.61 %, respectively. All of the findings show that the W-ZnO film is more suitable for the fabrication of PSCs than the ZnO film. In a nutshell, the synthesis of W-ZnO NPs employing green and eco-friendly methods, mediated by Aloe vera extract as the reducing agent, offers in this study a novel approach to enhancing solar cell efficiency with the simple spin coating fabrication technique.

Synergistic effects of the physical modification and chemical passivation enabling efficient perovskite solar cells

Inverted perovskite solar cells (IPSCs) with poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as hole transport materials exhibit superior stability and low-temperature processibility. However, the hydrophobicity of PTAA renders it difficult to prepare high-quality perovskite films due to the low wettability of perovskite precursor solutions, resulting in poor crystallization of perovskites and undesirable interface properties of PTAA/perovskites. Herein, a porous layer of Al2O3 nanoparticles functionalized using 2-thenoylacetonitrile (2-T-OACN) molecules is incorporated into the PTAA/perovskite interface. The physical adhesion of Al2O3 nanoparticles on the PTAA layer could enhance the surface wettability for perovskite precursor solutions, resulting in uniform perovskite films being realized on the PTAA layer. Meanwhile, 2-T-OACN adsorbed on the Al2O3 nanoparticles could form C=O··· Pb2+ and C≡N ···Pb2+ coordination interactions with the bottom surface of perovskites, thus passivating the defects at the PTAA/perovskite interface. Moreover, the electron-rich thiophene groups in 2-T-OACN molecules further promote interfacial charge carrier transport and thus significantly lower the interfacial recombination. Consequently, the IPSCs show a high efficiency of 23.3 %, which is largely improved compared with that of 19.4 % efficiency for control IPSCs. The synergistic strategy of the physical modification and chemical passivation provides a feasible approach for modulating the crystallization of perovskites and buried interface properties for IPSCs.

Enhancing performance of low-temperature fabricated inverted planar perovskite solar cells through triple-cation perovskite optimization

Perovskite solar cells have garnered significant attention due to the rapidly advancing power conversion efficiency(PCE). Recently, there has been significant interest in enhancing the performance of perovskite solar cells through Cs+ doping. However, the optimal concentration of Cs+ varies between inverted and positive structures, influenced by factors such as cell design, fabrication processes, and performance optimization requirements. In this study, we designed and prepared a novel inverted structure triple cations FA/MA/Cs perovskite solar cell at a low temperature. We observed that the quality of perovskite films can be obviously improved by doping an appropriate amount of Cs+, but excessive Cs+ will destabilize the perovskite structure, leading to rapid film decomposition in ambient air. Our results indicate that employing higher concentrations of Cs+, specifically 10 % and 15 %, leads to superior performance and enhanced stability. Notably, the perovskite solar cell incorporating 10%-Cs exhibits larger grain sizes, uniform particle distribution, and its highest PCE achieves 16.41 %. Our research provides a straightforward and cost-effective strategy for improving the performance of inverted perovskite solar cells utilizing triple cations.

Surface passivation enables efficient and stable inverted perovskite solar cells by 6-(Trifluoromethyl)pyridine-3-amidinehydrochloride

The inverted p-i-n PSCs are gradually gaining more attention since they are generally more stable and can employ low-cost transport materials. However, the interfaces between the perovskite and the charge transport layers contribute to major power conversion efficiency (PCE) loss and instability. Here, we use a material of 6-(Trifluoromethyl)pyridine-3-amidinehydrochloride (CF3-PyFACl) to molecularly engineer the interface between the perovskite and electron transport layer. The interface modification results in suppressed nonradiative recombination, and improved interfacial contact. A PCE of 23.17 % is demonstrated, with open-circuit voltage (Voc) and fill factor (FF) of 1.169 V and 84.1 %, respectively. The unencapsulated device retains >80 % of the initial performance after 400 h continuous light soaking.

Interfacial layer with a dibenzofulvene-bridged triphenylamine core for efficient and stable inverted perovskite solar cells

Considering the energy level cascade, introducing a hole transport layer (HTL) between the NiOx and perovskite layers has become a common and effective strategy to enhance the performance of inverted perovskite solar cells (PSCs). Herein, we designed and synthesized three hole-transporting interfacial layers (TPAD, TPAO, and TPAS) based on a dibenzofulvene-bridged triphenylamine (TPA) core to fabricate efficient and stable inverted NiOx-based PSCs. Dibenzofulvene, known for its sp²-hybridized structure, offers superior planarity and molecular stacking, and it easily bonds with triphenylamine derivatives, resulting in unique light-harvesting and charge mobility properties for optoelectronic applications. Specifically, diphenylamine, dimethoxy diphenylamine, and dimethylthio diphenylamine were used as end-capping units for TPAD, TPAO, and TPAS, respectively. The NiOx-based inverted PSC devices fabricated with TPAS as an interfacial layer effectively modified NiOx to improve energy level alignment, enhance film quality and crystallinity, and improve carrier transport, leading to a high-quality perovskite layer and superior interface contact behavior. Consequently, this device yielded a highly efficient cell performance of 20.30 %, surpassing those using TPAD (19.29 %) and TPAO (18.78 %) as interfacial layers, and significantly outperforming devices using only NiOx (17.69 %). Additionally, the champion cell exhibited negligible hysteresis and long-term stability. These findings demonstrate a facile approach to preparing multifunctional TPA-based hole transport materials and showcase the efficient performance of inverted cells based on a triphenylamine dibenzofulvene-based interfacial layer, contributing to the development of high-efficiency inverted PSCs.

Enhancement of inverted structure perovskite solar cell by CZTS nanoparticles

Inverted structure perovskite solar cells have attracted much attention in recent years due to their reliable operational stability, low residual, and low-temperature fabrication process. In the past few years, to accelerate their commercialization, the focus of research on the inverted structure perovskite solar cells was on the power conversion efficiency increasing. In this study nanoparticles of Cu2ZnSnS4 (CZTS) were doped into the PEDOT:PSS film as the hole transport layer (HTL) and then the interface carrier recombination quenching was observed. Consequently, it leads the s to charge carrier's collection enhancement of the Inverted perovskite solar cells. Compared to other types of HTLs, the use of CZTS HTL reduces the amount of interaction of the HTL film and the perovskite film, which results in an increment of the stability of the solar cell over time.

Molecule-triggered strain regulation and interfacial passivation for efficient inverted perovskite solar cells

Molecule-triggered strain regulation and interfacial passivation for efficient inverted perovskite solar cells

Ambient Air Processed Inverted Inorganic Perovskite Solar Cells with over 21 % Efficiency Enabled by Multifunctional Ethacridine Lactate

AbstractAll‐inorganic cesium lead triiodide perovskites (CsPbI3) have attracted increasing attention due to their good thermal stability, remarkable optoelectronic properties, and adaptability in tandem solar cells. However, N2‐filled glovebox is generally required to strictly control the humidity during film fabrication due to the moisture‐induced black‐to‐yellow phase transition, which remains a great hinderance for further commercialization. Herein, we report an effective approach via incorporating multifunctional ethacridine lactate (EAL) to mitigate moisture invasion and enable the fabrication of efficient inverted (p‐i‐n) CsPbI3 perovskite solar cells (PSCs) under ambient condition. It is revealed that the lactate anions accelerate the crystallization of CsPbI3, shortening the exposure time to moisture during film fabrication. Meanwhile, the conjugated backbone and multiple functional groups in the ethacridine cations can interact with I− and Pb2+ to reduce the undesired defects, stabilize the perovskite structure and facilitate the charge transport in the film. Moreover, EAL incorporation also leads to better energy alignment, thus favoring charge extraction at both upper and bottom interfaces. Consequently, the device efficiency and stability are enormously enhanced, with the champion efficiency reaching 21.08 %. This even surpasses the highest value reported for the devices fabricated in glovebox, representing a record efficiency of inverted all‐inorganic PSCs.

Ambient Air Processed Inverted Inorganic Perovskite Solar Cells with over 21 % Efficiency Enabled by Multifunctional Ethacridine Lactate.

All-inorganic cesium lead triiodide perovskites (CsPbI3) have attracted increasing attention due to their good thermal stability, remarkable optoelectronic properties, and adaptability in tandem solar cells. However, N2-filled glovebox is generally required to strictly control the humidity during film fabrication due to the moisture-induced black-to-yellow phase transition, which remains a great hinderance for further commercialization. Herein, we report an effective approach via incorporating multifunctional ethacridine lactate (EAL) to mitigate moisture invasion and enable the fabrication of efficient inverted (p-i-n) CsPbI3 perovskite solar cells (PSCs) under ambient condition. It is revealed that the lactate anions accelerate the crystallization of CsPbI3, shortening the exposure time to moisture during film fabrication. Meanwhile, the conjugated backbone and multiple functional groups in the ethacridine cations can interact with I- and Pb2+ to reduce the undesired defects, stabilize the perovskite structure and facilitate the charge transport in the film. Moreover, EAL incorporation also leads to better energy alignment, thus favoring charge extraction at both upper and bottom interfaces. Consequently, the device efficiency and stability are enormously enhanced, with the champion efficiency reaching 21.08 %. This even surpasses the highest value reported for the devices fabricated in glovebox, representing a record efficiency of inverted all-inorganic PSCs.

Repairing Interfacial Defects in Self-Assembled Monolayers for High-Efficiency Perovskite Solar Cells and Organic Photovoltaics through the SAM@Pseudo-Planar Monolayer Strategy.

Lately, carbazole-based self-assembled monolayers (SAMs) are widely employed as effective hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). Nevertheless, these SAMs tend to aggregate in solvents due to their amphiphilic nature, hindering the formation of a monolayer on the ITO substrate and impeding effective passivation of deep defects in the perovskites. In this study, a series of new SAMs including DPA-B-PY, CBZ-B-PY, POZ-B-PY, POZ-PY, POZ-T-PY, and POZ-BT-PY are synthesized, which are employed as interfacial repairers and coated atop CNph SAM to form a robust CNph SAM@pseudo-planar monolayer as HSL in efficient inverted PSCs. The CNph SAM@pseudo-planar monolayer strategy enables a well-aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss. As a result, the POZ-BT-PY-modified PSC realizes an impressively enhanced solar efficiency of up to 24.45% together with a fill factor of 82.63%. Furthermore, a wide bandgap PSC achieving over 19% efficiency. Upon treatment with the CNph SAM@pseudo-planar monolayer, also demonstrates a non-fullerene organic photovoltaics (OPVs) based on the PM6:BTP-eC9 blend, which achieves an efficiency of 17.07%. Importantly, these modified PSCs and OPVs all show remarkably improved stability under various testing conditions compared to their control counterparts.

Judicious Fluorination of Perovskite Quantum Wells Enables Over 25% Efficiency in Inverted Solar Cells

AbstractThe photovoltaic performance of inverted perovskite solar cells (PSCs) is often hindered by trap‐induced non‐radiative recombination and photochemical degradation occurring at the upper interfaces and the grain boundaries of perovskite films. Herein, ortho‐, meta‐, and para‐isomers of fluorophenylethylammonium iodine (F‐PEAI) organic spacer molecules are evaluated for the construction of perovskite quantum wells (2D or quasi‐2D, PQWs) to encapsulate 3D perovskites. Among the three variants, p‐F‐PEAI leads to the most symmetric charge distribution and the weakest steric hindrance which resulting in reinforced interactions with PbI2 and perovskite, the enhanced out‐of‐plane orientation is confirmed by Grazing incidence wide‐angle X‐ray scattering (GIWAXS) results. Density functional theory and crystal orbital Hamilton population (COHP) calculations further confirm that p‐F‐PEAI engages most strongly with the perovskite structure. Moreover, transmission electron microscopy (TEM) characterization is used to illustrate that p‐F‐PEAI‐assisted 2D PQWs effectively passivate both the grain boundaries and surfaces of perovskites. This configuration facilitates effective surface passivation, improves charge carrier transport, and significantly suppresses non‐radiative recombination. The resultant inverted PSCs achieve an excellent power conversion efficiency (PCE) of 25.03% with a fill factor (FF) of 85.11%. The unencapsulated devices exhibit enhanced long‐term stability under ambient environments and continuous light illumination.