High Power Conversion Efficiency Research Articles

Natural Dextran as an Efficient Interfacial Passivator for ZnO‐Based Electron‐Transport Layers in Inverted Organic Solar Cells

AbstractCompared to conventional organic solar cells (OSCs) with acidic PEDOT:PSS as the hole transport layer (HTL), inverted OSCs (i‐OSCs) with zinc oxide (ZnO) as the electron transport layer (ETL) display significant advantages in terms of high stability. However, an obvious limitation in i‐OSCs is that the sol‐gel processed ZnO layers possess detrimental defects at the interface, which hinders the improvement of its photovoltaic performance. To address this problem, a natural, and green dextran (Dex) is used as an efficient interfacial passivator to modify the ZnO layer, thereby achieving enhanced device performance in i‐OSCs. The introduction of the Dex passivator efficiently suppresses the interfacial recombination loss, resulting in higher power conversion efficiencies (PCEs). Interestingly, Dex‐passivated ZnO exhibits broad applications as an ETL for different types of i‐OSCs, including fullerene, non‐fullerene, and all‐polymer OSCs, in which the D18:Y6 system gives the highest PCE of 18.32%. This is one of the highest values reported for binary i‐OSCs. Moreover, the application of Dex significantly improves the device stability, and the T80 lifetimes based on PM6:Y6, D18:Y6, and PM6:PY‐IT exceed 1500 h. These results imply that Dex is an excellent interfacial passivator for ZnO‐based ETL for high‐efficiency and stable i‐OSCs.

Poly(amic acid)-Polyimide Copolymer Interfacial Layers for Self-Powered CH3NH3PbI3 Photovoltaic Photodiodes

Hybrid organohalide perovskites have received considerable attention due to their exceptional photovoltaic (PV) conversion efficiencies in optoelectronic devices. In this study, we report the development of a highly sensitive, self-powered perovskite-based photovoltaic photodiode (PVPD) fabricated by incorporating a poly(amic acid)-polyimide (PAA-PI) copolymer as an interfacial layer between a methylammonium lead iodide (CH3NH3PbI3, MAPbI3) perovskite light-absorbing layer and a poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) hole injection layer. The PAA-PI interfacial layer effectively suppresses carrier recombination at the interfaces, resulting in a high power conversion efficiency (PCE) of 11.8% compared to 10.4% in reference devices without an interfacial layer. Moreover, applying the PAA-PI interfacial layer to the MAPbI3 PVPD significantly improves the photodiode performance, increasing the specific detectivity by 49 times to 7.82 × 1010 Jones compared to the corresponding results of reference devices without an interfacial layer. The PAA-PI-passivated MAPbI3 PVPD also exhibits a wide linear dynamic range of ~103 dB and fast response times, with rise and decay times of 61 and 18 µs, respectively. The improved dynamic response of the PAA-PI-passivated MAPbI3 PVPD enables effective weak-light detection, highlighting the potential of advanced interfacial engineering with PAA-PI interfacial layers in the development of high-performance, self-powered perovskite photovoltaic photodetectors for a wide range of optoelectronic applications.

Wafer-scale monolayer MoS2 film integration for stable, efficient perovskite solar cells.

One of the primary challenges in commercializing perovskite solar cells (PSCs) is achieving both high power conversion efficiency (PCE) and sufficient stability. We integrate wafer-scale continuous monolayer MoS2 buffers at the top and bottom of a perovskite layer through a transfer process. These films physically block ion migration of perovskite into carrier transport layers and chemically stabilize the formamidinium lead iodide phase through strong coordination interaction. Effective chemical passivation results from the formation of Pb-S bonds, and minority carriers are blocked through a type-I band alignment. Planar p-i-n PSCs (0.074 square centimeters) and modules (9.6 square centimeters) with MoS2/perovskite/MoS2 configuration achieve PCEs up to 26.2% (certified steady-state PCE of 25.9%) and 22.8%, respectively. Moreover, the devices show excellent damp heat (85°C and 85% relative humidity) stability with <5% PCE loss after 1200 hours and notable high temperature (85°C) operational stability with <4% PCE loss after 1200 hours.

A facile approach for fabricating efficient and stable perovskite solar cells.

Perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs) can be produced using a variety of methods, such as different fabrication methods, device layout modification, and component and interface engineering. The efficiency of a perovskite solar cell is largely dependent on the overall quality of the perovskite thin-film in every scenario. The utilization of spin-coating followed by the antisolvent pouring (ASP) method is prevalent in nearly all fabrication techniques to achieve superior perovskite thin-films. Nevertheless, there are a few guidelines that must be followed precisely when using the ASP approach, including the antisolvent amount, duration, and area for dropping. The aforementioned challenging and necessary strategies frequently result in perovskite thin-films with pinholes, tiny grains, and broad grain boundaries, which impair the performance of PSCs. Therefore, the implementation of a straightforward approach that does not require the use of such complex ASP steps is crucial. Here, we employ a simple process that involves the hot-dipping of lead iodide (PbI2) thin-films in a hot solution of methylammonium iodide (MAI) and formamidinium iodide (FAI) in isopropanol (IPA) to produce high-quality perovskite thin-films. As the time required for the desired perovskite to crystallize is critical, we carefully examined various hot-dipping process times, such as 10 seconds, 20 seconds, 30 seconds, and 40 seconds. These time intervals yielded thin-films, which were named PSK-10, PSK-20, PSK-30, and PSK-40, respectively. Morphological and optoelectronic characterization demonstrated the high quality of the perovskite thin-films obtained through dipping PbI2 for 30 seconds. Consequently, the PSK-30-based PSCs produced higher PCEs of up to 21.52% compared to those of the ASP-based devices (20.79%). Furthermore, the unsealed PSCs prepared with PSK-30 and ASP were assessed for 252 hours at 25 °C and 40-45% relative humidity in order to determine their operational stability. The ASP-based device showed poor stability, retaining only 10% of its original PCE, whereas the PSK-30-based device retained 70% of its initial PCE. These results offer a new and viable approach for producing highly efficient and stable PSCs.

Heteroatomic molecules for coordination engineering towards advanced Pb-free Sn-based perovskite photovoltaics.

As an ideal eco-friendly Pb-free optoelectronic material, Sn-based perovskites have made significant progress in the field of photovoltaics, and the highest power conversion efficiency (PCE) of Sn-based perovskite solar cells (PSCs) has been currently approaching 16%. In the course of development, various strategies have been proposed to improve the PCE and stability of Sn-based PSCs by solving the inherent problems of Sn2+, including high Lewis acidity and easy oxidation. Notably, the recent breakthrough comes from the development of heteroatomic coordination molecules to control the characteristics of Sn-based perovskites, which are considered to be vital for realizing efficient PSCs. In this review, the up-to-date advances in the design of heteroatomic molecules and their key functions in the fabrication of Sn-based perovskite films are comprehensively summarized. Firstly, the design principles of heteroatomic coordination molecules and their impact on the colloidal chemistry, crystallization dynamics, and defect properties of Sn-based perovskites are introduced. Then, state-of-the-art heteroatomic coordination molecules for efficient Sn-based PSCs are discussed in terms of their heteroatom types and functional groups. Lastly, we shed some light on the current challenges and future perspectives regarding the rational design of heteroatomic coordination molecules for further boosting the performance of Sn-based PSCs.

Functionalized Substrates for Reduced Nonradiative Recombination in Metal-Halide Perovskites.

Reducing nonradiative recombination is crucial for minimizing voltage losses in metal-halide perovskite solar cells and achieving high power conversion efficiencies. Photoluminescence spectroscopy on complete or partial perovskite solar cell stacks is often used to quantify and disentangle bulk and interface contributions to nonradiative losses. Accurately determining the intrinsic loss in a perovskite layer is key to analyzing the origins of nonradiative recombination and developing defect engineering strategies. Here, we study perovskite films on glass and indium-tin-oxide-covered glass substrates, functionalized with a range of different molecules, using absolute and transient photoluminescence. We find that grafting these substrates with 1,6-hexylenediphosphonic acid (HDPA) effectively reduces the nonradiative losses in perovskite films for a series of perovskite semiconductors with bandgaps ranging from 1.26 to 2.28 eV. The results suggest that perovskites processed on HDPA-functionalized substrates suffer the least from nonradiative recombination and thus approach the properties of a defect-free semiconductor.

Regulated Crystallization Through Intermolecular Interactions Bridging for Efficient Tin‐Based Perovskite Solar Cells

AbstractTin halide perovskite (THP) has emerged as a promising lead‐free material for high‐performance solar cells, attracting significant attention for their potential use for energy conversion. However, the rapid crystallization of THP due to its high Lewis acidity and easy oxidation of Sn2+ leads to poor morphology and rampant defects in the resulting perovskite films. These strongly hamper the advances in efficiency and stability in THP solar cells. Herein, a comprehensive crystallization regulation strategy is demonstrated by introducing methyl carbazate (C2H6N2O2, MeC) to regulate the crystallization kinetics of perovskite through inter‐molecular interactions. The coordination bonds (O…Sn) and hydrogen bonds (N─H…O) between MeC and perovskite bridge the perovskite lattice together, helping suppress the oxidation of Sn2+, meanwhile, restraining the fast crystallization of perovskite in the precursor solution, by enhancing nucleation sites. More importantly, the connection by MeC can reduce the deep‐level trap state defect density, significantly restraining non‐radiative recombination and improving the carrier lifetime. Consequently, this facile strategy offers valuable insights into THP crystallization kinetics and allows an enhanced high power conversion efficiency from 10.43% to 14.02% to be achieved with good stability.

High‐Efficiency and Stable Perovskite Solar Cells Enabled by Halogen‐Free Cosolvent‐Processed Pyrazine‐Based Dopant‐Free Hole Transport Material

ABSTRACTThe complex molecular structures of electron donor (D)–acceptor (A) polymers provide a wealth of useful hints for producing high power conversion efficiency (PCE) as hole transport materials (HTMs) in perovskite solar cells (PVSCs). Given the recent improvements in PCE, various features are focused on altering the functionalities of HTMs. In this study, a pyrazine‐based acceptor is fused with two known donors benzodithiophene (BDT) and dithienobenzodithiophene (DTBDT) to synthesize two new D–A type polymers (NBD‐Pyz and NDT‐Pyz) to employ them as dopant‐free HTM in PVSCs. The insertion of pyrazine moiety downshifted the energy levels and enhanced coplanarity for both the HTMs. NBD‐Pyz can significantly lower the trap density and passivate the perovskite layer. More interestingly, the NBD‐Pyz HTM performs better than NDT‐Pyz, exhibiting higher hole mobility and better solubility in 2‐methyl anisole (2MA) and o‐xylene. Moreover, a 2MA/o‐xylene cosolvent‐processed dopant‐free polymeric NBD‐Pyz HTM‐based device achieved a champion PCE of 22.9%. Unlike NDT‐Pyz and Spiro‐OMeTAD‐based PVSCs, the unencapsulated NBD‐Pyz devices were more stable, retaining almost 90% of their initial efficiency after 1000 h. In addition, excellent thermal stability was demonstrated by the resulting PVSCs without encapsulation. image

Isomerism Effect of 3D Dimeric Acceptors for Non-Halogenated Solvent-Processed Organic Solar Cells with 20 % Efficiency.

Organic photovoltaic materials that can be processed via non-halogenated solvents are crucial for the large-area manufacturing of organic solar cells (OSCs). However, the limited available of electron acceptors with adequate solubility and favorable molecular packing presents a challenge in achieving efficient non-halogenated solvent-processed OSCs. Herein, inspired by the three-dimensional dimeric acceptor CH8-4, we employed a molecular isomerization strategy to synthesize its isomers, CH8-4A and CH8-4B, by tuning the position of fluorine (F) atom in the central unit. The differing intramolecular fluorine-sulfur non-covalent interactions among these isomers led to differences in molecular pre-aggregation abilities (CH8-4B<CH8-4<CH8-4A) in o-xylene (o-XY) solution, which significantly influence the film-forming process and the resultant morphological characteristics. Among these, the blend film of CH8-4, characterized by moderate molecular pre-aggregation, achieved optimal bi-continuous donor/acceptor phase separation. Consequently, the o-xylene processed PM6 : CH8-4 device achieved a power conversion efficiency (PCE) of 18.1 %, outperforming that of two other devices. By incorporating L8-BO-D as a guest acceptor, we attained an impressive PCE of 20.0 % for the CH8-4-based ternary device, alongside a high PCE nearing 16 % for the mini-module (13.5 cm2). Our findings underscore the potential of isomerism in 3D dimer acceptors to enhance the performance of eco-friendly OSCs.

Nanoscale Balance of Energy Loss and Quantum Efficiency for High-Efficiency Polythiophene-Based Organic Solar Cells.

Polythiophene donors offer scalable and cost-effective solutions for the organic photovoltaic industry. A thorough understanding of the structure-property-performance relationship is essential for advancing polythiophene-based organic solar cells (PTOSCs) with high power conversion efficiencies (PCEs). Herein, we develop two polythiophene donors─PTTz-CN and PTTz-CN(T2)─to verify the energy loss-quantum efficiency relationship. The strong preaggregation property of PTTz-CN improves quantum efficiency in spite of high nonradiative recombination energy loss, while PTTz-CN(T2) chains are weakly preaggregated, causing low quantum efficiency, accompanied by low nonradiative recombination energy loss though. Synergistically optimized energy loss and quantum efficiency are achieved by judiciously mixing PTTz-CN and PTTz-CN(T2), delivering outstanding PCEs of up to 16.4% in the PTOSC system and 19.6% in an archetype of a high-performing OSC containing the optimal PTTz-CN:PTTz-CN(T2) composition. We highlight the significance of a desirable balance between energy loss and quantum efficiency via molecular interaction tuning of polythiophene donors to improve the PTOSC performances.

A Systematic Analysis of The Current 2D Perovskite Engineering Approach and Future Prospects

Perovskite solar cells (PSCs) have become a hot topic in the photovoltaic studies. Although perovskite has excellent photoelectric properties including adjustable bandgap, high power conversion efficiency (PCE) performance, high electron transport, the three-dimensional perovskite commonly studied is often unstable, short life, and subject to environmental interference especially heat and humidity. So two-dimensional perovskites have been studied and studied. This paper introduces the 2D materials and 2D perovskite solar cells. And then several new works of surface engineering on 2D perovskite solar cells including passivation strategies, interface engineering and orientation of crystallization on perovskite films are mentioned and concluded, thereby providing a future understanding to improve and balance the efficiency and stability of 2D PSCs. Even though the existing strategies for optimizing two-dimensional perovskite are abundant and have certain rules, more essential two-dimensional perovskite properties to improve efficiency and stability need to be studied, so that two-dimensional perovskite will have more possibilities in industrial production.

Study of Thermalization Mechanisms of Hot Carriers in BABr-Added MAPbBr3 for the Top Layer of Four-Junction Solar Cells.

The hot carrier multi-junction solar cell (HCMJC) is an advanced-concept solar cell with a theoretical efficiency greater than 65%. It combines the advantages of hot carrier solar cells and multi-junction solar cells with higher power conversion efficiency (PCE). The thermalization coefficient (Qth) has been shown to slow down by an order of magnitude in low-dimensional structures, which will significantly improve PCE. However, there have been no studies calculating the Qth of MAPbBr3 quantum dots so far. In this work, the Qth values of MAPbBr3 quantum dots and after BABr addition were calculated based on power-dependent steady-state photoluminescence (PD-SSPL). Their peak positions in PD-SSPL increased from 2.37 to 2.71 eV after adding BABr. The fitting shows that, after adding BABr, the Qth decreased from 2.64 ± 0.29 mW·K-1·cm-2 to 2.36 ± 0.25 mW·K-1·cm-2, indicating a lower relaxation rate. This is because BABr passivates surface defects, slowing down the carrier thermalization process. This work lays the foundation for the theoretical framework combining perovskite materials, which suggests that the appropriate passivation of BABr has the potential to further reduce Qth and make MAPbBr3 QDs with BABr modified more suitable as the top absorption layer of HCMJCs.

Minimizing Performance Loss in Blade‐Coated Large‐Area Perovskite Solar Cells Via Semi‐Sealed Gas Quenching

AbstractGas‐quenching of perovskite wet films is widely used in upscaling perovskite solar cells (PSCs). However, due to uneven and turbulent gas stream generated by traditional approaches through air knife or air gun, it is a challenge to induce homogeneous nucleation and produce high‐quality perovskite films suitable for large‐area PSCs. Here this work presents a semi‐sealed gas quenching (SSGQ) strategy that produces homogeneous low‐velocity large‐area high‐pressure gas flow to extract low‐boiling‐point solvents effectively, while leaving behind perovskite intermediates undisturbed that then turn into large crystalline grains. As a result, the SSGQ‐processed perovskite films exhibit improved crystallinity and reproducibility, suppressed defect density and residual stress, as well as compact buried interface and large‐scale uniformity. Such blade‐coated large‐area (1.0 cm2) PSCs with carbon and metal electrodes achieve high power conversion efficiencies (PCEs) of 19.5% and 23.3% (20.5% and 24.2% for 0.04 cm2), both with the lowest PCE loss of ≤1.0% among reported works. This work presents a scalable and affordable approach for fabricating high‐quality perovskite films and high‐performance perovskite photovoltaics, paving the way to PSC commercialization.

19.5%‐Efficiency Organic Solar Cells with High Thickness Tolerance and Exceptional Device Stability Enabled by TEMPO‐Functionalized Perylene Diimide as a Cathode Interface Layer

AbstractThe cathode interface material is pivotal for achieving excellent photovoltaic performance and device stability in organic solar cells (OSCs). However, currently, few interface materials can simultaneously satisfy multiple criteria such as low cost, high efficiency, insensitivity to film thickness, and good stability. To address this challenge, a novel perylene diimide (PDI) derivative, P‐C3T is designed and synthesized, by incorporating stable free radical unit TEMPO and polar quaternary ammonium salt as side chains. P‐C3T is facile to synthesize and cost‐effective, while also exhibiting good conductivity and excellent ohmic contact characteristics in OSCs. When utilized as the cathode interface material, the device based on D18:L8‐BO achieves a remarkable power conversion efficiency (PCE) of 19.52%, which is one of the highest levels reported for binary single‐junction OSCs. Notably, devices based on P‐C3T exhibit remarkable insensitivity to film thickness, with the PCE remaining at 95% of the initial efficiency even at a thickness of 40 nm. Furthermore, P‐C3T‐based OSCs demonstrate exceptional storage stability and improved light stability. In summary, with its high PCE, excellent thickness insensitivity, and good stability, P‐C3T is anticipated to be a promising candidate material for large‐area roll‐to‐roll processing of OSCs.

A Numerical Simulation Study of the Impact of Kesterites Hole Transport Materials in Quantum Dot-Sensitized Solar Cells Using SCAPS-1D.

Energy generation and storage are critical challenges for developing economies due to rising populations and limited access to clean energy resources. Fossil fuels, commonly used for energy production, are costly and contribute to environmental pollution through greenhouse gas emissions. Quantum dot-sensitized solar cells (QDSSCs) offer a promising alternative due to their stability, low cost, and high-power conversion efficiency (PCE) compared to other third-generation solar cells. Kesterite materials, known for their excellent optoelectronic properties and chemical stability, have gained attention for their potential as hole transport layer (HTL) materials in solar cells. In this study, the SCAPS-1D numerical simulator was used to analyze a solar cell with the configuration FTO/TiO2/MoS2/HTL/Ag. The electron transport layer (ETL) used was titanium dioxide (TiO2), while Cu2FeSnS4 (CFTS), Cu2ZnSnS4 (CZTSe), Cu2NiSnS4 (CNTS), and Cu2ZnSnSe4 (CZTSSe) kesterite materials were evaluated as HTLs. MoS2 quantum dot served as the absorber, with FTO as the anode and silver as the back metal contact. The CFTS material outperformed the others, yielding a PCE of 25.86%, a fill factor (FF) of 38.79%, a short-circuit current density (JSC) of 34.52 mA cm-2, and an open-circuit voltage (VOC) of 1.93 V. This study contributes to the advancement of high-performance QDSSCs.

Fine Tuning the Glass Transition Temperature and Crystallinity by Varying the Thiophene-Quinoxaline Copolymer Composition.

In recent years, the design and synthesis of high-performing conjugated materials for the application in organic photovoltaics (OPVs) have achieved lab-scale devices with high power conversion efficiency. However, most of the high-performing materials are still synthesised using complex multistep procedures, resulting in high cost. For the upscaling of OPVs, it is also important to focus on conjugated polymers that can be made via fewer simple synthetic steps. Therefore, an easily synthesised amorphous thiophene-quinoxaline donor polymer, TQ1, has attracted our attention. An analogue, TQ-EH that has the same polymer backbone as TQ1 but with short branched side-chains, was previously reported as a donor polymer with increased crystallinity. We have synthesised copolymers with varied ratios between octyloxy and branched (2-ethylhexyl)oxy-substituted quinoxaline units having the same polymer backbone, with the aim to control the aggregation/crystallisation behaviour of the resulting copolymers. The optical properties, glass transition temperatures and degree of crystallinity of the new copolymers were systematically examined in relation to their copolymer composition, revealing that the composition can be used to fine-tune these properties of conjugated polymers. In addition, multiple sub-Tg transitions were found from some of the polymers, which are not commonly or clearly seen in other conjugated polymers. The new copolymers were tested in photovoltaic devices with a fullerene derivative as the acceptor, achieving slightly higher performances compared to the homopolymers. This work demonstrates that side-chain modification by copolymerisation can fine-tune the properties of conjugated polymers without requiring complex organic synthesis, thereby expanding the number of easily synthesised polymers for future upscaling of OPVs.

Enhance Photo-Stability of Up-Scalable Organic Solar Cells: Suppressing Radical Generation in Polymer Donors.

The power conversion efficiency (PCE) of single-junction organic solar cells (OSCs) has been promoted above 20%. Device up-scaling draws more and more research attentions. Besides the high PCE for devices with up-scalable fabrication methods and conditions, achieving high stability simultaneously is essential for pushing industrialization of this technology. Here, the stability of the state-of-the-art OSCs blade-coated in air with non-halogenated solvents in a wide thickness range is thoroughly investigated. The losses in short-circuit current density under photo-thermal stress strongly depend on processing conditions. Devices with less crystalline phases in unit thickness show faster generation of trap states and hence strongly reduced charge collection efficiency. Through in-depth photo-chemical, photo-physical, and morphological characterizations during ageing, faster generation of radicals in PM6 for active layers with more amorphous structures is identified as the cause for device degradation. Increasing the crystallinity of active layer films for suppressing radical generation in polymer donors is critical to enhance the photo-thermal stability of devices processed in air with a wide thickness range.

Characterization of Ultrathin Layers in Perovskite/TOPCon Tandem Cells With Photoelectron Spectroscopy Utilizing Advanced Data Evaluation Methods

Next generation solar cells like tunnel oxide passivated contacts (TOPCon) or perovskite/TOPCon tandem solar cells require efficient interface passivation by ultrathin organic or inorganic layers to uncover their true efficiency potential. Especially the microstructure and the Si suboxide content of the tunnel oxide in poly-Si(Ox)/SiO2/c-Si TOPCon stacks have been shown to have a tremendous influence on macroscopic device properties. Similarly, perovskite/ITO interface modification by a self-assembled monolayer (SAM) molecule is necessary to achieve high power conversion efficiencies of the perovskite sub cell. However, the characterization of such thin film structures and the interfacial composition is challenging. In this contribution, we present characterization results of ultrathin passivation layers using angle-resolved X-ray photoelectron spectroscopy (XPS) and advanced data evaluation routines, including maximum entropy methods and analyses of inelastically-scattered electron background data. In particular, the interfaces in the stacks (1) partially oxidized a-Si/SiO2/c-Si and (2) 2PACz/ITO after different thermal treatment were investigated. It could be shown that already a ~5 nm thin SiNx layer prevents unwanted oxidation from ambient during cooldown of TOPCon-like stacks and that annealing above 100 °C can convert a 2PACz multilayer to a 2PACz monolayer on an ITO substrate.

Chloride Engineering for Boosting Perovskite Photovoltaics: Impact on Precursor Coordination, Crystallization, and Film Quality.

Perovskite solar cells (PSCs) have seen rapid advancements over the past decade, driven by their exceptional optoelectronic properties and high power conversion efficiencies. Cl-based additives strategy has significantly contributed to these advancements by enhancing crystallinity, improving preferred orientation, and optimizing the surface morphology of perovskite films. This review provides a comprehensive summary of recent advancements and insights into the critical role of Cl-based additives in perovskite photovoltaics, focusing on the mechanisms behind Cl incorporation and its effects on film and device performance. First, the impact of Cl on precursor solution coordination and colloidal characteristics is discussed. Then, how Cl-based additives influence the phase transitions of perovskites, including methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3), and 2D perovskites is examined. Furthermore, the impact of Cl-based interfacial treatments on perovskite film quality is explored. Based on these insights, the overall impact of Cl treatments is also reviewed on the properties of perovskite films. Finally, a brief overview of the remaining challenges and future perspectives are provided to guide ongoing research efforts toward optimizing Cl additive engineering for high-performance PSCs.

Equally high efficiencies of organic solar cells processed from different solvents reveal key factors for morphology control

AbstractThe power conversion efficiency of organic solar cells (OSCs) is exceeding 20%, an advance in which morphology optimization has played a significant role. It is generally accepted that the processing solvent (or solvent mixture) can help optimize morphology, impacting the OSC efficiency. Here we develop OSCs that show strong tolerance to a range of processing solvents, with all devices delivering high power conversion efficiencies around 19%. By investigating the solution states, the film formation dynamics and the characteristics of the processed films both experimentally and computationally, we identify the key factors that control morphology, that is, the interactions between the side chains of the acceptor materials and the solvent as well as the interactions between the donor and acceptor materials. Our work provides new understanding on the long-standing question of morphology control and effective guides to design OSC materials towards practical applications, where green solvents are required for large-scale processing.