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Power conversion efficiencies (PCEs) of the methylammonium‐free (MA‐free) perovskite solar cells (PSCs) are constantly lagging behind those of the most extensively researched triple cation mixed PSCs due to their subpar perovskite films. Here, two guanidine‐based passivation agents are proposed, that are, sulfaguanidine (S‐Gua) and 1‐acetylguanidine (A‐Gua) that can be applied to optimize the film quality of MA‐free perovskite for minimizing the efficiency discrepancy between the two types of PSCs. Through strong coordination with Pb2+ and hydrogen bonding with formamidinium (FA+), the two passivation additives can reduce bulk defects and suppress non‐radiative recombination, which in turn enhance the charge extraction and transfer efficiency. Consequently, the S‐Gua‐ and A‐Gua‐treated devices achieve PCEs of 24.34% and 23.77%, respectively. Both PCEs are greater than that of the control device (23.03%), and the 24.34% PCE is comparable with that of the best MA‐free inverted PSCs with narrower bandgaps. Moreover, the S‐Gua‐treated devices maintain 89.3% and 82.0% of their initial PCEs after aging for 800 h and heating (85 °C) for 340 h in ambient air without any encapsulation, respectively. This work offers comprehensive insights into the use of guanidine‐based additives to achieve high‐quality perovskite films and subsequently state‐of‐the‐art MA‐free PSCs. [ABSTRACT FROM AUTHOR]

M‐series molecules are one kind of promising acceptor‐donor‐acceptor (A‐D‐A)‐type acceptors for constructing high‐performance organic solar cells (OSCs). However, their power conversion efficiencies (PCEs) are lagging behind that of current state‐of‐the‐art OSCs, limited by the relatively low fill factor (FF) and photocurrent. Herein, combined strategies of layer‐by‐layer (LBL) deposition and interface engineering are conducted to systematically improve light utilization and thus PCEs for M36‐based OSCs. Through choosing a proper processing solvent, a PCE of 17.3% with an FF of 77.9% is achieved for the resulting LBL devices, much higher than those (15.9%/74.0%) from the blend‐casting devices. The improvement is assigned to the favorable morphological evolution that facilitates carrier generation and transport as well as reduces charge recombination. More importantly, light‐harvesting of the active layers can be enhanced upon employing a self‐assembled monolayer of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) instead of the widely used PEDOT:PSS as the hole‐selecting layer, due to the decreased parasitic absorption of the former. Consequently, 2PACz‐based LBL devices exhibit significantly increased photocurrent, affording a PCE up to 18.2%, which is the highest among the reported A‐D‐A‐type acceptor‐based OSCs. These results deliver important strategies to enhance the performance of OSCs and thus highlight the great potential of M‐series acceptors for practical applications. [ABSTRACT FROM AUTHOR]

The rapid advancements in material research for lead‐free inorganic metal halide perovskites have fueled the pathway to design environmentally benign solar‐cells to cater the energy requirements for future generations. The vacancy‐ordered double‐perovskite Cs2SnI6 with an optimum band‐gap (≈1.3 eV), high absorption coefficient (≈105 cm−1), ambi‐polar charge carrier transport, and high structural and compositional stability coupled with simple cost‐effective solution‐based synthesis techniques seems to be an excellent candidate to design air‐stable high‐efficiency solar‐cell‐based applications. The review focusses on the structure–property relationship in Cs2SnI6 and its critical dependency on growth precursors, conditions, and methods. The recent advancements in material and additive engineering to obtain phase‐pure uniform and continuous Cs2SnI6 films and myriad methods to modulate its optoelectronic properties are summarized. The nature, origin, and type of charge‐carriers in intrinsic and doped Cs2SnI6 are extensively discussed. The applications of Cs2SnI6 in different solar‐cell configurations are critically reviewed and its recent progress and challenges to achieve the ultimate theoretical Shockley–Queisser limit of 30–33% is presented. The recent experimental findings on the stability and performance of Cs2SnI6‐based solar‐cells under ambient and controlled conditions would be discussed to highlight its feasibility for the design and development of air‐stable high‐efficiency solar‐cells. [ABSTRACT FROM AUTHOR]

Porphyrin derivatives are widely used as donors in organic solar cells (OSCs) due to their excellent optical and electrochemical properties. Although porphyrins can be functionalized at the meso‐ and β‐positions, only meso‐functionalized porphyrins have been reported as OSCs. Consequently, a direct comparison of the properties of porphyrins functionalized at these two positions is needed. The synthesis of two similar D–π–A–π–D materials is described herein and these compounds contain benzothiadiazole as the acceptor core and two Ni‐porphyrins as donors functionalized at the meso‐ and β‐positions to give RC19 and RC20, respectively. The optical and electrochemical properties of these compounds are reported. All‐small‐molecule OSCs based on RC19:TOCR1 and RC20:TOCR1 active layers show power conversion efficiencies (PCEs) of 13.72% and 5.20%, respectively. It should be noted that the PCE of 13.72% obtained for RC19:TOCR1 devices is, to one's knowledge, the highest value reported for porphyrin‐based binary OSCs. The higher PCE obtained for RC19 is due to its higher photon harvesting ability, more efficient exciton dissociation and charge transfer, balanced charge transport, and lower bimolecular and trap‐assisted recombination. [ABSTRACT FROM AUTHOR]

Remarkable achievements have been made in the development of perovskite solar cells (PSCs) with a rapidly boosting rate of power conversion efficiencies (PCEs) from 3.8% to 26.1%. Nevertheless, the toxicity of lead (Pb) elements and the hygroscopicity of organic cations in high‐efficiency PSCs severely hamper the commercialization of this technology. Consequently, Pb‐free all‐inorganic PSCs have received increasing attention recently to resolve the above‐mentioned toxicity and instability problems. Among various Pb‐free all‐inorganic halide perovskites, cesium bismuth iodide (CBI)‐based perovskites have gained particular attention as light absorbers in PSCs due to the tunable/small bandgaps, long carrier diffusion length/lifetime, and superb sunlight absorption coefficients. Nevertheless, the PCEs of CBI‐based PSCs are still far away from Pb‐based organic–inorganic counterparts because of the low structural dimensions and inferior perovskite film quality. Herein, the recent advances of CBI‐based perovskites as light‐absorbing materials in Pb‐free all‐inorganic PSCs are reviewed by emphasizing the distinct structural/optical/electronic properties and currently existing limitations. Additionally, several distinct strategies to boost the PCEs and robusticity of CBI‐based PSCs are presented. Finally, the unsolved key problems and future directions of CBI‐based PSCs are proposed, aiming to provide important insights for the further development of CBI‐based PSCs to realize sustainable, nontoxic, high‐performance perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

The goal of bifacial technology is to increase the efficiency of solar cells (SC) by capturing albedo sunlight and converting it to electrical energy. The use of triple‐cation mixed‐halide perovskite solar cells (PSC) has sparked a lot of curiosity and could be the potential for improved power conversion efficiency (PCE) associated with traditional PSCs. Herein, n–i–p‐configured triple‐cation mixed‐halide‐based bifacial PSC is studied using the SC capacitance simulator 1D tool. Through our simulation, the impact of thickness in electron and hole transport layers (ETL and HTLs), defect density, doping density, and the thickness of the light‐harvesting layer on the device performance is examined. With an optimal design, the device exhibits an absolutely staggering efficiency of 25.28% from the front side and around 17.19% from the rear. This cell, due to its high albedo absorption, linearly enhances the short‐circuit current; hence, it overcomes the classical current‐matching limit of ordinary PSCs. The proposed device FTO/TiO2/[Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3]/CuSbS2 has a remarkable efficiency that increases linearly with albedo, making it very appealing for new, high‐efficiency solar applications. [ABSTRACT FROM AUTHOR]

Two benzotrithiophene (BTT)‐based 2D covalent organic frameworks (2D COFs) are synthesized and characterized. The BTT and triphenylamine units (either tris(4‐aminophenyl)amine or N4,N4‐bis(4′‐amino‐[1,1′‐biphenyl]‐4‐yl)‐[1,1′‐biphenyl]‐4,4′‐diamine) are alternately connected for the two BTT‐based COFs, namely TABT–COF and BABT–COF, respectively. The obtained BTT‐based COFs exhibit high crystallinity, high surface area, and excellent thermal stability. In addition, these two COFs are further utilized as efficient additives by doping into the perovskite layer of perovskite solar cells (PSCs). The incorporation of BTT‐based COFs can be exploited as an efficient nucleation template, enabling the regulation of perovskite crystallinity. The power conversion efficiencies of the champion PSCs with TABT–COF and BABT–COF achieve 18.10% and 18.56%, respectively, outperforming that (16.58%) of the control device. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSC) are a potential candidate for next‐generation photovoltaic technology. Despite the significant advancements in the field of PSCs, the ongoing development of stable and efficient metal halide perovskite materials, along with their successful integration into photovoltaic applications, remains challenges. These challenges originate from the diverse range of device structures and perovskite compositions, requiring meticulous consideration and optimization. Traditional trial‐and‐error methods are characterized by their sluggishness and labor‐intensive nature. Recently, the emergence of extensive datasets and advancements in computer hardware have facilitated the utilization of machine learning (ML) across multiple domains, including in various fields for material discovery and experimental optimization. Herein, the fundamental procedure of ML is briefly introduced, and latest progress of ML in the materials development and solar cell fabrication is comprehensively reviewed. The utilization of ML in PSCs at all stages of design can be categorized into four main areas: screening perovskite material, fabrication process optimization, device structure optimization, and understanding mechanism. The challenges and outlooks on the future development of ML are finally discussed. It is highly expected that this review can offer valuable guidance for the design and development of highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Herein, FTO/TiO2/Sb2S3/Au solar cell characteristics via SCAPS‐1D modeling are examined. The research begins with device modeling of the Sb2S3 conventional solar cell based on experimental data, which results in excellent agreement with the power conversion efficiency recorded in the literature of ≈4.72%. The influence of several factors on the characteristics of conventional solar cells is then investigated, including Sb2S3 thickness, carrier concentration, bulk and interface defects, and buffer layer type (TiO2, WS2, and CdS). An optimal efficiency of 9.97%, open‐circuit voltage (Voc) of 0.96 V, short‐circuit current (Jsc) of 19.69%, and fill factor (FF) of 52.26% are found for the FTO/WS2/Sb2S3/Au optimized solar cell. Finally, the influence of NiO as the back surface field and parasitic resistance (Rs and Rsh) on the performance of Sb2S3 solar cells is investigated. The innovative solar cell design (FTO/WS2/Sb2S3/NiO/Au) with NiO thickness of 20 nm, Rs < 2 Ω cm−2, and Rsh > 700 Ω cm−2 yields a high efficiency of more than 14.38%, FF > 68.93%, Voc > 1 V, and Jsc > 20.67 mA cm−2. These qualities allow for the large‐scale manufacture of a solar cell by including it in a manufacturing workflow. [ABSTRACT FROM AUTHOR]

The electrical properties of hole transport layers (HTL) are critical factors for the high performance of lead sulfide quantum dot solar cells (PbS CQDSCs). Herein, the impacts of doping the organic HTL PTB7‐Th with lithium bis(trifluoromethanesulfonimide) (LiTSFI) on the performance of quantum dot solar cells are explored and a notable enhancement in the fill factor is observed. A series of analytical characterizations of the doped HTLs are performed and it is found that doping with LiTFSI significantly deepens the Fermi level of the HTL, thereby improving the charge separation ability within the devices. Additionally, the conductivity of doped HTL is also improved. By optimizing the doping conditions, the doped device achieves a maximum power conversion efficiency of 12.68%. This doping strategy of organic HTL promotes the development of lead sulfide quantum dot solar cell techniques. [ABSTRACT FROM AUTHOR]

Tin oxide has been the mainstream as the electron transport layer for highly efficient perovskite solar cells due to advantages such as high mobility, high transmittance, and strong UV stability. Realizing high‐quality SnO2 layer at low temperature can widen the range of potential applications on both rigid and flexible substrates. Herein, a seed‐assisted growth strategy is developed for the preparation of SnO2 layer at low temperature (100 °C) and the seeds in precursor solution provide preferential nucleation sites. The SnO2 layer via seed‐assisted growth exhibits higher conductivity and mobility which are more than twice those of control samples because of enhanced crystallinity. The resulting solar cells show high Voc of 1.189 V, contributing to a high power conversion efficiency of 25.26%. To current knowledge, this is the highest efficiency for perovskite solar cells with SnO2 layer formed at low temperature (≤100 °C). Contributed by the high‐quality SnO2 layer prepared at low temperature, a high power conversion efficiency over 22% for flexible perovskite solar cells is also achieved. [ABSTRACT FROM AUTHOR]

Solvent additive can be used to regulate active layer morphology and improve photovoltaic performance of organic solar cells (OSCs). Herein, the PM6:Y6:PC71BM ternary bulk heterojunction OSCs are prepared by introducing 1,8‐diiodooctane (DIO) and 1‐chloronaphthalene (CN) as binary additives. On the basis of optimizing the photovoltaic performance with CN additive, the addition of trace amounts of DIO additive further improves the molecular packing of active layer and induces Y6:PC71BM acceptor on the surface of active layer. With the optimized active layer morphology, the CN and DIO binary additives restrict carrier recombination and improve charge transport efficiently, and the prepared PM6:Y6:PC71BM ternary OSCs with binary additives demonstrate a high short‐circuit current density of 27.15 mA cm−2 and a fill factor of 76.79%, and yield an improved power conversion efficiency of 17.53%, which is higher than that of devices without additives (16.50%) and with DIO (16.79%) or CN additive (17.21%). Binary solvent additives engineering provides an effective strategy to finely regulate active morphology and boost photovoltaic performance of ternary OSCs. [ABSTRACT FROM AUTHOR]

Developing new polymerized small molecular acceptor (PSMA) is pivotal for improving the performance of all‐polymer solar cells. On the basis of this newly developed CH‐series small molecule acceptors, two PSMAs are reported herein (namely PZC16 and PZC17, respectively). To reduce the molecular torsion caused by the traditional aromatic π‐bridges, non‐aromatic conjugated units (ethynyl for PZC16 and vinylene for PZC17) are adopted as the linkers and their effect on the photo‐physical properties as well as the device performance are systematically investigated. Both polymer acceptors exhibit co‐planar molecular conformation, along with broad absorption ranges and suitable energy levels. In comparison with the PM6:PZC16 film, the PM6:PZC17 film exhibits more uniform phase separation in morphology with a distinct bi‐continuous network and better crystallinity. The PM6:PZC17‐binary‐based devices exhibit a satisfactory PCE of 16.33%, significantly higher than 9.22% of the PZC16‐based devices. Impressively, PM6:PZC17‐based large area device (ca. 1 cm2) achieves an excellent PCE of 15.14%, which is among the top performance for reported all‐polymer solar cells (all‐PSCs). [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) are a promising low‐cost thin‐film photovoltaic technology while the fabrication of transparent conductive oxide (TCO) and metal electrodes still remains a factor that hinders the scaling‐up and commercialization of OSCs. Carbon‐based materials are regarded as potential alternatives due to their excellent properties, such as low cost, solution processibility, high conductance, and good chemical stability. In this mini‐review, the recent progress of carbon‐based materials such as graphite, carbon nanosheets, graphene, and carbon nanotubes to replace the TCO and metal electrodes of OSCs is surveyed. The preparation methods of different carbon‐based materials are also discussed. Based on current progress, we summarize the outlooks and challenges of carbon‐based electrodes. We anticipate this mini‐review will inspire more research efforts to develop high‐performance and OSC‐matched carbon materials for more efficient and stable carbon‐electrode‐based OSCs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have drawn lots of attention because of their rapid development and great potential in large‐area flexible electronics. Recently, volatile solid additives have been widely used in optimizing morphologies of active layers and improving device performances for nonfullerene (NF)‐based OSCs. Most solid additives, however, still suffer severe problems such as unsuitable volatile temperatures and requirement of extra solvent additives. Herein, a new solid additive 2,7‐dibromo‐9,9‐dimethylfluorene (DBDMF) with a high crystallinity and suitable volatile temperature as an additive for NF‐based OSCs is designed. DBDMF can suppress the overaggregation of the nonfullerene acceptors (NFAs) and improve the material rearrangements after thermal annealing because of the good miscibility with the NFAs. As a result, DBDMF‐treated OSC devices display more favorable film morphologies and phase separation, well‐balanced charge mobilities, higher electron transfer rates, and better device stability. Consequently, the PM6:BTP‐BO‐4F binary system shows an outstanding power conversion efficiency of 17.2% from 15.3% with a simultaneous increase in the fill factor from 71.4 to 77.1%. Furthermore, DBDMF has been applied to other two active layers, manifesting the general applicability. This study demonstrates a feasible and promising approach to develop volatilizable solid additives for improving performance and stability of NF‐based OSCs. [ABSTRACT FROM AUTHOR]

The collaborative strategy of optical design and charge transport dynamics optimization can provide double guarantee to achieve high‐efficient planar perovskite solar cells (PSCs). Herein, WO3−X nanorods with tunable localized surface plasmon resonance (LSPR) effect are introduced at the interface between perovskite and hole transport layer (HTL) via antisolvent method during the preparation of perovskite films. The photocurrent of WO3−X nanorods‐based devices significantly increases due to the extension of absorption region caused by LSPR effect. The charge transfer at the perovskite/HTL interface is also accelerated due to the electromagnetic near‐field enhancement via the LSPR effect. The synchronized improvement in photocurrent and charge transfer by WO3−X nanorods leads to a power conversion efficiency of 21.14% in MAPbI3‐based PSCs. This work not only provides an effective approach to enhance the photovoltaic performance of PSCs, but also demonstrates the potential application of inorganic oxide semiconductors with LSPR in other optoelectronic devices. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of organic solar cells (OSCs) is improved dramatically in recent years and now approaches >19% for single‐junction cells and >20% for tandem cells. Therefore, the practical use of OSCs is becoming a reality. This perspective summarizes the state of the art of OSC characteristics and discusses the challenges that remain in further improving PCE. The short‐circuit current density (J SC) of the state‐of‐the‐art OSCs almost approaches 30 mA cm−2. As the internal quantum efficiencies of these devices exceed 90%, for further improvement in J SC, it is necessary to suppress reflection at interfaces and increase the active layer thickness to absorb as many photons as possible. Further suppression of the nonradiative voltage loss is imperative, as there is still large room for improvement compared to inorganic and perovskite counterparts. Hence, increasing the exciton lifetime and photoluminescence quantum yield of nonfullerene acceptors are pivotal to improving the open‐circuit voltage of OSCs. The fill factors of the latest OSCs approach 80%; however, because the optimized active layer thickness remains ≈100 nm, further suppression of bimolecular charge recombination is needed. Finally, this perspective discusses to what extent PCE can be improved and what can be done to achieve this.

A group of regioregular polymer acceptors is synthesized by polymerizing Y6 moieties with different linker units including thiophene, vinylene, 2,2'‐bithiophene, and thieno[3,2‐b]thiophene, and their optoelectrical properties and photovoltaic performances are studied systematically. It is found that the linker units have significant impacts on the backbone planarity, conjugation, and hence optoelectrical properties of polymer acceptors. The vinylene‐based PYF‐V‐o polymer shows a smaller dihedral angle between the end groups and vinylene units and a more rigid polymer backbone, thus affording bathochromic absorption and better electron‐transporting capacity. As a result, the PM6:PYF‐V‐o based all‐polymer solar cells (all‐PSCs) are able to achieve the highest power conversion efficiency of 16.4% with an unprecedented small voltage loss of 0.49 V. Moreover, the PM6:PYF‐V‐o blend exhibits good resistance to environmental stressors and the air‐processed PM6:PYF‐V‐o cells can still maintain a high efficiency of 16.1%, which is the best air‐processed all‐PSC efficiency reported to date. This study provides the structural‐property guidance that can be used to facilitate the development of polymer acceptors for all‐PSCs. [ABSTRACT FROM AUTHOR]

Nonradiative recombination on perovskite surface and grain boundary largely constrains the efficiency and stability of photovoltaic devices. Surface passivation has proven to be the most effective strategy to suppress photogenerated carrier recombination. Herein, functional N‐hydroxysuccinimide (NHS) is incorporated in perovskite films by suppressing nonradiative losses both in surface and in grain boundary. The NHS molecules are located at the perovskite grain boundary and surface with good compability with the perovskite crystal network, which forms an effective barrier at the grain boundary to prevent the permeation of moisture. Equally important, the interactions between the CO group in NHS and perovskite undercoordinated groups (Pb2+ or Pb clusters) reduce the surface defects of the perovskite, yielding a minimal energy loss. The prolonged lifetime of carriers with NHS‐treated perovskites prevents the carrier quenching at the perovskite grain boundary and interface. As a result, open‐circuit voltage of the solar cell is up to 1.13 V with a power conversion efficiency (PCE) of 22.21%. The stability of the device is also significantly improved, wherein devices with NHS retain 81% of the initial PCE after 1000 h at room temperature. [ABSTRACT FROM AUTHOR]

Recently, the strategy of polymerized small‐molecule acceptors (PSMAs) has attracted extensive attention for applications in all‐polymer solar cells (all‐PSCs). Although side‐chain engineering is considered as a simple and effective strategy for manipulating polymer properties, the corresponding effect on photovoltaic performance of PSMAs in all‐PSCs has not been systemically investigated. Herein, a series of PSMAs based on the benzotriazole (BTz)‐core fused SMAs with different N‐alkyl chains including branched 2‐butyloctyl, linear n‐octyl, and methyl on the BTz unit, namely PZT‐C12, PZT‐C8, and PZT‐C1, respectively, is presented. Comparative studies show that the size of alkyl chains has a significant impact on the solid‐state behavior of PZT polymers, which in turn affects their light absorption and charge transporting capacities, and subsequently the all‐PSC performances. When combining with the polymer donor PBDB‐T, PZT‐C1 affords a champion power conversion efficiency of 14.9%, compared to 13.1% of PZT‐C12, and 13.8% of PZT‐C8 in the resultant all‐PSCs, mainly benefiting from its better crystallinity and the more favorable blend morphology. This work emphasizes the importance of optimizing side‐chain substituents on PSMAs for improving the device efficiency of all‐PSCs. [ABSTRACT FROM AUTHOR]

During the past five years, plentiful efficient polymer solar cells (PSCs) developed rapidly with the application of small molecules as non‐fullerene acceptors (NFAs). Although most of the synthesized NFAs have planar backbones, the backbone twisted NFAs have exhibited impressive performances in devices with wide‐bandgaps polymer donors like J52 and PBDB‐T. To boost the performances of PSCs based on NFAs with contorting backbone, a systematic study of a twisted NFA (i‐IEICO‐4F), with J52 and its halogenated counterparts was conducted, because the attached halogen atoms have strong effects on the frontier molecular orbitals and the aggregation properties of the polymers. Despite the polymers possessing similar absorption spectra, they exhibited continuously deepened molecular energy levels. Among the three polymers, the device based on J52‐2F and i‐IEICO‐4F achieved the lowest efficiency of 11.78 %. Although differed in open‐circuit voltages and short‐circuit current densities, the J52‐ and J52‐2Cl‐based devices successfully acquired enhanced fill factors of 67.0 % and 67.6 %, giving rise to enhanced efficiencies of 12.47 % and 12.69 %. The superior performance of J52‐2Cl‐based device stems from its deepened molecular energy levels, improved charge transport properties, and better morphological features, demonstrating the important influence of halogenation substitution on the characteristic regulation of wide‐bandgap conjugated polymers for high‐performance PSCs. [ABSTRACT FROM AUTHOR]

A donor–acceptor copolymer based on thiazole substituted benzodithiophene (BDTTz) (donor unit) and thieno[3,4‐c]pyrrole‐4‐6‐dione (TPD) (acceptor unit) P(BDTTz‐TPD) denoted as P132 is investigated. P132 shows an absorption profile from 300 to 680 nm and the low‐lying highest occupied molecular orbital (HOMO) energy level of −5.54 eV. P132 as donor along with fullerene derivative (PC71BM) or nonfullerene denoted as BThIND‐Cl as acceptor are used for the fabrication of polymer solar cells. The P132:BThIND‐Cl‐based polymer solar cell shows high open‐circuit voltage as compared with P132:PC71BM which is attributed to the upshifted lowest unoccupied molecular orbital level of BThIND‐Cl and low energy loss. Moreover, P132:BThIND‐Cl attains higher short‐circuit current than that for P132:PC71BM which is attributed to the broader absorption spectra and low optical band gap of BThIND‐Cl, which leads to high light‐harvesting ability of the P132:BThIND‐Cl active layer. The polymer solar cells based on P132:PC71BM and P132:BThIND‐Cl attain power conversion efficiencies of 7.03% and 15.52%, respectively. The charge transport is more balanced in P132:BThIND‐Cl and results in a high value of fill factor. Small energy loss in P132:BThIND‐Cl‐based PSCs is attributed to the low HOMO offsets between P132 and BThIND‐Cl. [ABSTRACT FROM AUTHOR]

Simultaneously controlling defects and film morphology at the buried interface is a promising approach to improve the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs). Here, two new donor‒acceptor type semiconductive covalent organic frameworks (COFs) are developed, COF TPA and COF ICZ . The carefully designed COFs structure not only effectively regulates the morphology and defects of the buried interface film, but also realizes the alignment with the energy level of the perovskite film and enhances the extraction and transmission of the interface charge. Among them, COF ICZ -treated inverted PSCs achieved a maxmum PCE of 25.68% (certified 25.14%), the inverted PCE reached a minimum PCE of 22.92% for 1 cm 2 device. The efficiency of inverted PSCs with a 1.68 eV wide bandgap reached 22.92%, which is the highest datum of the reported 1.68 eV wide bandgap PSC. This lays the groundwork for the commercialization of perovskite/silicon tandem solar cells. Additionally, the unencapsulated devices demonstrated a high degree of stability during operational use and when subjected to conditions of high humidity and temperature., (© 2024 Wiley‐VCH GmbH.)

Abstract A group of regioregular polymer acceptors is synthesized by polymerizing Y6 moieties with different linker units including thiophene, vinylene, 2,2’‐bithiophene, and thieno[3,2‐b]thiophene, and their optoelectrical properties and photovoltaic performances are studied systematically. It is found that the linker units have significant impacts on the backbone planarity, conjugation, and hence optoelectrical properties of polymer acceptors. The vinylene‐based PYF‐V‐o polymer shows a smaller dihedral angle between the end groups and vinylene units and a more rigid polymer backbone, thus affording bathochromic absorption and better electron‐transporting capacity. As a result, the PM6:PYF‐V‐o based all‐polymer solar cells (all‐PSCs) are able to achieve the highest power conversion efficiency of 16.4% with an unprecedented small voltage loss of 0.49 V. Moreover, the PM6:PYF‐V‐o blend exhibits good resistance to environmental stressors and the air‐processed PM6:PYF‐V‐o cells can still maintain a high efficiency of 16.1%, which is the best air‐processed all‐PSC efficiency reported to date. This study provides the structural‐property guidance that can be used to facilitate the development of polymer acceptors for all‐PSCs.

At present, a variety of benzo[1,2‐b:4,5‐b′]dithiophene (BDT)‐based polymer donors are designed and synthesized, which have made great progress toward achieving high power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Despite many advantages of benzo[1,2‐b:4,5‐b′]difuran (BDF) compared with BDT unit, the overall performance of BDF polymer‐based PSCs lags far behind that of the counterpart BDT‐based polymers. Recently, great advances have been achieved in BDF polymer‐based PSCs with the highest PCEs over 16%, suggesting that BDF‐based polymers have the significant potential to catch up or even surpass the performance of BDT‐based polymers. In this review, the recent advances of BDF polymers in PSCs are first summarized and then the design strategies and the chemical structure–performance relationships of BDF polymers are discussed. Finally, perspectives on the future development of BDF polymers for high‐efficiency PSCs are provided. [ABSTRACT FROM AUTHOR]

Characterizing the electrical parameters of perovskite solar cells (PSCs) usually requires a lot of time to fabricate complete devices. Here, machine learning (ML) is used to reduce the device fabrication process and predict the electrical performance of PSCs. Using ML algorithms and 814 valid data cleaned from 2735 peer‐reviewed publications, ML prediction models are built for bandgap, conduction band minimum, valence band maximum of perovskites, and electrical parameters of PSCs. These prediction models have excellent accuracy, and the root mean square error of the prediction models for bandgap and power conversion efficiency (PCE) reaches 0.064 eV and 1.58%, respectively. Among the many factors that affect the performance of PSCs, those factors play a major role in the lack of comprehensive explanation. Through the prediction model of electrical parameters and Shapley Additive explanations theory, the factors affecting the PCE of PSCs are explained and analyzed. It can not only verify the objective physical laws from the perspective of ML, but also conclude that among the 13 features, the content of formamidinium/NH2CHNH2+ plays the most important role in improving the PCE of PSCs. These results show that ML has great application possibilities in the PSC field. [ABSTRACT FROM AUTHOR]

At present, a variety of benzo[1,2‐b:4,5‐b′]dithiophene (BDT)‐based polymer donors are designed and synthesized, which have made great progress toward achieving high power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Despite many advantages of benzo[1,2‐b:4,5‐b′]difuran (BDF) compared with BDT unit, the overall performance of BDF polymer‐based PSCs lags far behind that of the counterpart BDT‐based polymers. Recently, great advances have been achieved in BDF polymer‐based PSCs with the highest PCEs over 16%, suggesting that BDF‐based polymers have the significant potential to catch up or even surpass the performance of BDT‐based polymers. In this review, the recent advances of BDF polymers in PSCs are first summarized and then the design strategies and the chemical structure–performance relationships of BDF polymers are discussed. Finally, perspectives on the future development of BDF polymers for high‐efficiency PSCs are provided.

Abstract Side-chain engineering is an important strategy in designing novel polymer semiconductor materials for high-efficient organic solar cells. The use of trialkylsilyl side chains can improve the photovoltaic efficiency by decreasing the energy of the HOMO of the polymer and improving its crystallinity and hole mobility. Compared to simple linear derivatives, α-branching in the alkyl groups of trialkylsilyl side chains causes strong aggregation and excessive phase separation in the photoactive layer, leading to poor device performance. β-Branching of the alkyl groups has not yet been used in trialkylsilyl side chains. Herein, we describe a new polymer (J77) with triisobutylsilyl side chains to investigate the effect of β-branching on the molecular aggregation, optical properties, energy levels, and photovoltaic properties. We find that compared to α-branching, β-branching of alkyl groups in trialkylsilyl side chains significantly reduces aggregation. This enables J77 to form blend morphologies in films that provide high-efficient solar cells in combination with different non-fullerene acceptors. Moreover β-branching of the alkyl groups in trialkylsilyl side chains lowers the HOMO energy level of J77 and increases the open-circuit voltage of J77-based solar cells without sacrificing short-circuit current density or fill factor.

A dataset containing 599 data points from 146 publications on 2D/3D perovskite solar cells is analyzed using machine learning. The predictive models are developed for power conversion efficiency (PCE) using eXtreme Gradient Boosting regression, random forest regression and artificial neural networks while association rule mining is used to analyze the stability data to identify the descriptors leading to high stability 2D/3D cells. A predictive model is also developed for the bandgap to predict the missing values in the dataset for the use in PCE predictions. Models for both bandgap and PCE predictions are quite successful. The thickness of inorganic layer (n), radius of anion (Rx), and 2D cation (Rm) are found to be the most important descriptors for bandgap predictions; n and Rm, together with the bandgap, are found to be deterministic for PCE in regular cells while the bandgap, n, and conduction band energy of hole transport layer are the most influential descriptors in inverted structures. Association rule mining analysis for the stability indicates that the cells with layered perovskite structures are more stable while the 2D and 3D cations leading to the most stable cells are found to be butylammonium and formamidinium‐Cs mixed cation respectively. [ABSTRACT FROM AUTHOR]

Despite the significant progress made recently in all-polymer solar cells (all-PSCs), it is still quite challenging to achieve high open-circuit voltage (Voc) and short-circuit current density (Jsc) simultaneously in order to further improve their performance. The recent strategy of using selenophene to replace thiophene on the Y6 based polymer acceptors has resulted in significantly improved Jscs of the resulting all-PSCs. However, such modifications have also depressed Voc, which compromises the overall performance of the devices. Herein, we present the design and synthesis of a novel polymer acceptor, PYT-1S1Se, created by inserting an asymmetrical selenophene-fused framework to precisely manipulate optical absorption and electronic properties. Compared with the selenium-free analog, PYT-2S, and symmetrical selenium-fused analog, PYT-2Se, the PYT-1S1Se derived all-PSCs not only deliver optimized Jsc (24.1 mA cm−2) and Voc (0.926 V) metrics, but also exhibit a relatively low energy loss of 0.502 eV. Consequently, these devices obtain a record-high power conversion efficiency (PCE) of 16.3% in binary all-PSCs. This work demonstrates an effective molecular design strategy for balancing the trade-off between Voc and Jsc to achieve high-efficiency all-PSCs. [ABSTRACT FROM AUTHOR]

Interfacial layer materials play an important role in performance enhancement of organic solar cells (OSCs). Herein, the utilization of mixed‐metal Dawson‐type polyoxometalates, namely P2Mo3W15O62 (POM‐1) and P2Mo9W9O62 (POM‐2), as anode interlayer (AIL) materials, for efficiently collecting holes to boost the photovoltaic efficiency of OSCs, is explored. The increase in molybdenum substitution in the mixed‐metal POMs can lower the conduction band level and increase the reduction potential. Meanwhile, the high work function of POMs helps to remove the energy barrier in the hole collection, which solves the serious problem of Voc loss in OSCs. As a result, OSCs modified by POM‐2 can exhibit superior photovoltaic performance with power conversion efficiency of 14.8%. The results of Mott−Schottky analysis, current density−light intensity dependence, and excitons dissociation probability indicate the efficient hole collection and the depressed charge recombination in the POM‐2‐based OSC device. By means of fabricating OSCs, the effect of the two POM‐based AILs on various photoactive layers is also investigated, and POM‐2 exhibits excellent hole collection capability. Moreover, the advantages of low‐cost and solution‐processable conduct make POM‐2 a promising candidate as the AIL material for future mass production of OSCs. [ABSTRACT FROM AUTHOR]

Recently, scientists are more devoted to designing and synthesizing organic perovskite solar cells for attaining high power conversion efficiency (PCE). Herein, a series of small molecules as hole transport materials with A–π–D–π–A framework, namely (DFA1, DFA2, DFA3, and DFA4) having triphenylamine (TPA)‐based central donor core unit (A1–A4) end‐capped acceptor moieties linked via thiophene spacer is designed theoretically to study optoelectronic and photovoltaic properties. MPW1PW91 hybrid functional in conjunction with 6‐31G** basis set is found the best method to investigate the optoelectronic and photovoltaic properties. All hole transport materials (HTMs) possess a high open‐circuit voltage (0.98–1.41 V) with downshifted highest occupied molecular orbital energy values (−4.98 to −5.41 eV) by tailoring of electron‐withdrawing acceptor moieties. Meanwhile, appropriate elongation of π‐conjugated acceptor units is advantageous for enhancing the molar absorption coefficient and intermolecular electronic coupling. The highest hole mobility and charge transfer integral owing to lower hole reorganization energies indicate these molecules are best for HTMs. DFA1‐DFA4 has a power conversion efficiency of up to 24% which authenticates that these HTMs have excellent photovoltaic attributes compared to the reported reference DFH. The present computational investigation validates the efficacy of the designed techniques and opens a new route for designing high‐performance dopant‐free HTMs in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract Recently, by elaborately designing nonfullerene acceptors and selecting suitable polymer donors great progresses have been made towards binary organic solar cells (OSCs) with power conversion efficiencies (PCEs) over 15%. Ternary organic photovoltaics by introducing a third component into the host binary system is recognized to be highly effective to elevate the performance through extending the light absorption, manipulating the recombination behavior of the carriers, and improving the morphology of the active layer. In this work, we synthesized a new electron-acceptor ZITI-4F matching it with the wide-bandgap polymer donor PBDB-T The PBDB-T:ZITI-4F-based OSC showed a high PCE of 12.33%. After introducing 40% of PC71BM as the third component, the ternary device achieved an improved PCE of 13.40% with simultaneously improved photovoltaic parameters. The higher performance of the ternary device can be attributed to the improved and more balanced charge mobility, reduced bimolecular recombination, and more favorable morphology. These results indicate that the cooperation of a fullerene-based acceptor and a nonfullerene acceptor to fabricate ternary OSCs is an effective approach to optimizing morphology and therefore to increase the performance of OSCs.

Great progress has been made in organic solar cells (OSCs) in recent years, especially after the report of the highly efficient small-molecule electron acceptor Y6. However, the relatively low open circuit voltage ( V OC ) and unbalanced charge mobilities remain two issues that need to be resolved for further improvement in the performance of OSCs. Herein, a wide-band-gap amorphous acceptor IO-4Cl, which possessed a shallower lowest unoccupied molecular orbital (LUMO) energy level than Y6, was introduced into the PM6:Y6 binary system to construct a ternary device. The mechanism study revealed that the introduced IO-4Cl was alloyed with Y6 to prevent the overaggregation of Y6 and offer dual channels for effective hole transportation, resulting in balanced hole and electron mobilities. Taking these advantages, an enhanced V OC of 0.894 V and an improved fill factor of 75.58% were achieved in the optimized PM6:Y6:IO-4Cl-based ternary device, yielding a promising power conversion efficiency (PCE) of 17.49%, which surpassed the 16.72% efficiency of the PM6:Y6 binary device. This work provides an alternative solution to balance the charge mobilities of PM6:Y6-based devices by incorporating an amorphous high-performance LUMO A-D-A small molecule as the third compound.

Perovskite solar cells (PSCs) have achieved revolutionary progress during the past decades with a rapidly boosting rate in power conversion efficiencies from 3.8% to 26.1%. However, high-efficiency PSCs with organic hole-transporting materials (HTMs) suffer from inferior long-term stability and high costs. The replacement of organic HTMs with inorganic counterparts such as metal oxides can solve the above-mentioned problems to realize highly robust and cost-effective PSCs. Nevertheless, the widely used simple metal oxide-based HTMs are limited by the low conductivity and poor light transmittance due to the fixed atomic environment. As an emerging family of inorganic HTMs, complex metal oxides with superior structural/compositional flexibility have attracted rapidly increasing interest recently, showing superior carrier conductivity/mobility and superb light transmittance. Herein, the recent advancements in the design and development of complex metal oxide-based HTMs for high-performance PSCs are summarized by emphasizing the superiority of complex metal oxides as HTMs over simple metal oxide-based counterparts. Consequently, several distinct strategies for the design of complex metal oxide-based HTMs are proposed. Last, the future directions and remaining challenges of inorganic complex metal oxide-based HTMs for PSCs are also presented. This review aims to provide valuable guidelines for the further advancements of robust, high-efficiency, and low-cost PSCs., (© 2024 Wiley‐VCH GmbH.)

Restricted by the energy-gap law, state-of-the-art organic solar cells (OSCs) exhibit relatively low open-circuit voltage (V OC ) because of large nonradiative energy losses (ΔE nonrad ). Moreover, the trade-off between V OC and external quantum efficiency (EQE) of OSCs is more distinctive; the power conversion efficiencies (PCEs) of OSCs are still <15% with V OC s of >1.0 V. Herein, the electronic properties and aggregation behaviors of non-fullerene acceptors (NFAs) are carefully considered and then a new NFA (Z19) is delicately designed by simultaneously introducing alkoxy and phenyl-substituted alkyl chains to the conjugated backbone. Z19 exhibits a hypochromatic-shifted absorption spectrum, high-lying lowest unoccupied molecular orbital energy level and ordered 2D packing mode. The D18:Z19-based blend film exhibits favorable phase separation with face-on dominated molecular orientation, facilitating charge transport properties. Consequently, D18:Z19 binary devices afford an exciting PCE of 19.2% with a high V OC of 1.002 V, surpassing Y6-2O-based devices. The former is the highest PCE reported to date for OSCs with V OC s of >1.0 V. Moreover, the ΔE nonrad of Z19- (0.200 eV) and Y6-2O-based (0.155 eV) devices are lower than that of Y6-based (0.239 eV) devices. Indications are that the design of such NFA, considering the energy-gap law, could promote a new breakthrough in OSCs., (© 2024 Wiley‐VCH GmbH.)

Currently, high-performance polymerized small-molecule acceptors (PSMAs) based on ADA-type SMAs are still rare and greatly demanded for polymer solar cells (PSCs). Herein, two novel regioregular PSMAs (PW-Se and PS-Se) are designed and synthesized by using centrosymmetric (linear-shaped) and axisymmetric (banana-shaped) ADA-type SMAs as the main building blocks, respectively. It is demonstrated that photovoltaic performance of the PSMAs can be significantly improved by optimizing the configuration of ADA-type SMAs. Compared to the axisymmetric SMA-based polymer (PS-Se), PW-Se using a centrosymmetric SMA as the main building block exhibits better backbone coplanarity thereby resulting in bathochromically shifted absorption with a higher absorption coefficient, tighter interchain π-π stacking, and more favorable blend film morphology. As a result, enhanced and more-balanced charge transport, better exciton dissociation, and reduced charge recombination are achieved for PW-Se-based devices with PM6 as polymer donor. Benefiting from these positive factors, the optimal PM6:PW-Se-based device exhibits a higher power conversion efficiency (PCE) of 15.65% compared to the PM6:PS-Se-based device (8.90%). Furthermore, incorporation of PW-Se as a third component in the binary active layer of PM6:M36 yields ternary devices with an outstanding PCE of 18.0%, which is the highest value for PSCs based on ADA-type SMAs, to the best of the knowledge., (© 2024 Wiley‐VCH GmbH.)

Constructing 0D–2D mixed‐dimensional van der Waals (MvdW) heterostructures is an effective strategy to improve photovoltaic properties of photovoltaic devices. However, addressing the underlying mechanism on the role of array periodicity of 0D and thickness of 2D components on the photovoltaic properties at the atomic‐level still remains challenging. Herein, the interfacial charge transfer and photovoltaic conversion mechanism in C60/MoS2 0D–2D MvdWs based on the atomic‐bond‐relaxation consideration, Marcus theory, modified‐detailed balance principle, and first‐principles calculations are investigated. Compared with the case of monolayer MoS2, it is found that C60/MoS2 MvdW heterostructures have lower interface reflectivity and type II band alignment, leading to obvious improvement of power conversion efficiency (PCE) from 0.27% to 1.40%. Moreover, the photovoltaic properties can be tuned by changing the array periodicity of the C60 and the thickness of the MoS2, and the optimized PCE can be up to 5.35%. The results reveal that the modification of 0D C60 is an effective strategy to enhance the photovoltaic properties of MoS2‐based solar cells. [ABSTRACT FROM AUTHOR]

High‐performance organic photovoltaics (OPVs) with relatively thick active layers are essential for large‐scale production. Herein, series of OPVs with different active layer thicknesses are fabricated using PM6 as the donor and BP4T‐4F and BP3T‐4F with symmetric and asymmetric structures as acceptors. With the active layer thickness increasing from 100 to 300 nm, the power conversion efficiency (PCE) of BP3T‐4F‐based binary OPVs is slightly decreased from 15.37% to 14.40%, while the PCEs of BP4T‐4F‐based binary OPVs are markedly decreased from 16.89% to 14.99%. The two kinds of binary OPVs exhibit distinct PCEs and thickness tolerance features, which may be recombined into ternary OPVs using compatible BP3T‐4F and BP4T‐4F as alloyed acceptors. The ternary OPVs exhibit a slightly decreased PCE from 16.91% to 16.03% along with active layer thickness from 100 to 300 nm, benefiting from the well‐optimized phase separation in ternary active layers. It is worth highlighting that the fill factor (FF) of 71.47% is achieved in ternary thick‐film OPVs. The PCE of 16.03% and FF of 71.47% should be among the highest values among OPVs with 300 nm thick active layers. [ABSTRACT FROM AUTHOR]

All‐polymer solar cells (all‐PSCs) progressed tremendously due to recent advances in polymerized small molecule acceptors (PSMAs), and their power conversion efficiencies (PCEs) have exceeded 15 %. However, the practical applications of all‐PSCs are still restricted by a lack of PSMAs with a broad absorption, high electron mobility, low energy loss, and good batch‐to‐batch reproducibility. A multi‐selenophene‐containing PSMA, PFY‐3Se, was developed based on a selenophene‐fused SMA framework and a selenophene π‐spacer. Compared to its thiophene analogue PFY‐0Se, PFY‐3Se shows a ≈30 nm red‐shifted absorption, increased electron mobility, and improved intermolecular interaction. In all‐PSCs, PFY‐3Se achieved an impressive PCE of 15.1 % with both high short‐circuit current density of 23.6 mA cm−2 and high fill factor of 0.737, and a low energy loss, which are among the best values in all‐PSCs reported to date and much better than PFY‐0Se (PCE=13.0 %). Notably, PFY‐3Se maintains similarly good batch‐to‐batch properties for realizing reproducible device performance, which is the first reported and also very rare for the PSMAs. Moreover, the PFY‐3Se‐based all‐PSCs show low dependence of PCE on device area (0.045–1.0 cm2) and active layer thickness (110–250 nm), indicating the great potential toward practical applications. [ABSTRACT FROM AUTHOR]

In this research highlight, recent significant advances with hot‐assisted blade‐coating or air knife‐assisted blade‐coating of different perovskite compositions with bandgaps ranging from 1.3 eV to 1.9 eV (i.e. wide‐bandgap or small‐bandgap perovskites with mixed cations and anions, 2D/3D perovskites, Pb/Sn binary perovskites, and all‐inorganic perovskites) for single‐junction or tandem PSCs are discussed, with an emphasis on elucidating the distinct ink formulation engineering strategies, crystal growth mechanisms, crystallization kinetics, and optoelectronic properties of the different perovskite compositions. [ABSTRACT FROM AUTHOR]

In this study, the electronic properties and chemical stability of the Cu/CH3NH3PbI3 interface are investigated in situ by a combination of X‐ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy (SRPES). The morphology of Cu deposited perovskite surface is monitored by scanning electron microscopy. The results show that the Cu/CH3NH3PbI3 interface is very stable and no chemical reaction between Cu and the perovskite takes place. Moreover, a 0.45 eV interface dipole and a 0.15 eV upward band bending are obtained at the Cu/CH3NH3PbI3 interface. Based on these fundamental findings, a prototype of Cu/CH3NH3PbI3/NiOx/indium tin oxide solar cell device is constructed to check the power conversion efficiency (PCE) and device stability. Although no electron transport material is used in this device, it still exhibits decent performance. The PCE of the device reaches up to 9.99% and remains almost unchanged over a long‐time (49 d) storage in a N2‐filled glovebox. Through this study it is demonstrated that fundamental understanding of the interfacial structure of a perovskite solar cell is essential in pursuit of rational design of superior perovskite solar cells, and moreover, Cu is a promising electrode candidate for perovskite solar cells. [ABSTRACT FROM AUTHOR]

Herein, the synthesis of a new medium bandgap nonfullerene acceptor DBTBT‐IC consisting of di‐benzothieno [3,2‐b][1]‐benzothiophene DBTBT as the central donor unit and IC as terminal acceptor units and its use as the acceptor for the fabrication of single binary and ternary polymer solar cells is reported. DBTBT‐IC exhibits a medium optical bandgap of about 1.65 eV. When paired with the wide bandgap‐conjugated polymer PDTNIT as donor, the polymer solar cells based on the optimized PDTNIT:DBTBT‐IC active layer realized a power conversion efficiency of 12.34% (short‐circuit current = 8.06 mA cm−2, open‐circuit voltage = 1.12 V, and fill factor (FF) = 0.62) which is higher than that for the PDTNIT:PC71BM counterpart, i.e., 9.08 % (short‐circuit current=14.58 mA cm−2, open‐circuit voltage = 0.93 V, and FF = 0.67). When a small amount of PC71BM was introduced into the host PDTNIT:DBTBT‐IC binary layer, the polymer solar cell based on the optimized PDTNIT:PC71BM:DBTBT‐IC (1:0.3:0.9) ternary active layer attained an excellent power conversion efficiency of about 15.92 %, mainly due to the increase in short‐circuit current and FF. The increase in the short‐circuit current may be associated with the broader absorption profile of the ternary active layer as compared with the binary counterparts and more efficient exciton utilization, due the partial energy transfer from PC71BM to DBTBT‐IC. [ABSTRACT FROM AUTHOR]

Nonfullerene acceptor materials are getting more and more attention from the scientific community because of their various applications in photovoltaic energy devices. Herein, a series of eight new S‐shaped nonfullerene acceptors (SY1–SY8) with end‐capped molecular modeling of IDTP‐4F (R) is designed. These designed materials are theoretically characterized along with the reference molecule R to investigate their structural‐property relationship, photophysical, and optoelectronic properties with density functional theory and time dependent calculations. Moreover, the geometric specifications such as alignments of frontier molecular orbitals, excitation and binding energy, hole‐electron overlap, density of states, overlap density of states, molecular electrostatic potential, open circuit voltage, transition density matrix, and reorganizational energy of electron and hole have also been investigated and compared with the experimentally synthesized reference molecule R. A highly red‐shifting behavior along, with a high charge mobility of electrons is realized after these end‐capped modifications in all designed molecules. Moreover, all designed molecules have lower binding and excitation energies as compared to reference molecule R. After these analyses, it is realized that the newly designed molecules (SY1‐SY8) are better than R, thus these molecules are recommended to experimentalists for the future development of highly efficient OSCs. [ABSTRACT FROM AUTHOR]

A scalable and accessible photoactive formulation with a low synthetic complexity (SC) index is utilized in organic photovoltaic (OPV) fabrication. The formulation readily dissolves in nonchlorinated solvents, and the corresponding photoactive films can be processed by various coating methods to fabricate devices with power conversion efficiencies (PCEs) of 16.1% and 15.2% when using vacuum‐based molybdenum oxide and solution‐processable conducting polymer as the hole transporting layer in the inverted structure, respectively. This prepared device shows superior stability under light exposure. The PCE is maintained 94% of the initial values after 1080 h of light soaking at 100 mW cm−2. Furthermore, the figure of merit based on the ratio of the SC index and PCE indicates the benefit of this formulation for OPV manufacturing, showing the feasibility of commercialization. Eventually, a PCE of 10.3% is demonstrated for a mini‐module fabricated under ambient conditions, with an active area of 32.6 cm2. To our knowledge, this PCE is one of the largest values reported to date for a green solvent and an all‐solution‐processed OPV module with an inverted architecture. [ABSTRACT FROM AUTHOR]

Due to the impressive optoelectronic properties, metal–halide perovskites (MHPs) have drawn much attention in the field of next‐generation photovoltaics, and perovskite solar cells (PSCs) based on MHPs as light absorbers have reached a certified power conversion efficiency (PCE) of 25.5% in 2020. Despite the great progress, it is still challenging to fabricate high‐quality MHP films. Due to the "soft" ionic nature of MHPs, their polycrystalline films suffer from inevitable residual strain, which is found to not only be fatal to photovoltaic performance of PSCs, but also seriously accelerate the degradation of MHP film. As a result, understanding of strain in MHPs and the key role of strain engineering in improving the photovoltaic performance of PSCs have recently been extensively investigated. Herein, the recent progress of strain engineering in MHPs and their PSCs is systematically summarized. First, the origin of strain in MHPs and the impact of strain on the optoelectronic characteristics of MHPs are carefully discussed. Thereafter, the up‐to‐date studies focusing on strain engineering in PSCs are comprehensively reviewed. At last, the current challenges and future prospects in this field are highlighted. [ABSTRACT FROM AUTHOR]

Bulk‐heterojunction (BHJ) organic solar cells (OSCs) are prepared by a common one‐step solution casting of donor‐acceptor blends often encounter dynamic morphological evolution which is hard to control to achieve optimal performance. To overcome this hurdle, a generally applicable, sequential processing approach has been developed to construct high‐performance OSCs without involving tedious processes. The morphology of photoactive layers comprising a polymer donor (PM6) and a nonfullerene acceptor (denoted as Y6‐BO) can be precisely manipulated by tuning Y6‐BO layer with a small amount of 1‐chloronaphthalene additive to induce the structural order of Y6‐BO molecules to impact the blend phase. The results of a comparative investigation elucidate that such two‐step procedure can afford more favorable BHJ microstructure than that achievable with the single blend‐casting route. This translates into improved carrier generation and transport, and suppressed charge recombination. Consequently, the devices based on sequential deposition (SD) deliver a remarkable efficiency up to 17.2% (the highest for SD OSCs to date), outperforming that from the conventional BHJ devices (16.4%). The general applicability of this approach has also been tested on several other nonfullerene acceptors which show similar improvements. These results highlight that SD is a promising processing alternative to promote better photovoltaic performance and reduce production requirements. [ABSTRACT FROM AUTHOR]

To date, the power conversion efficiency (PCE) of lab‐scale organic solar cells (OSCs) has exceeded 17%, which heralds the bright future for commercial applications of OSCs. High‐performance OSCs with thick active layers are essential for large‐scale production. First, the relatively thick active layers should be more compatible with the roll‐to‐roll (R2R) large‐area processing, which is conducive to forming uniform and defect‐free active layers in the process of high‐speed, mass production. Second, the thick active layers can absorb more incident light in their spectral range, which helps thick‐film OSCs to obtain relatively high short‐circuit current density (JSC). So far, relatively little attention has been paid to thick‐film OSCs, and the PCE of thick‐film OSCs lags far behind its thin‐film analogues. Herein, the recent development of thick‐film OSCs is highlighted and the critical limit factors on the PCE of thick‐film OSCs are pointed out. Some strategies are highlighted to improve the efficiency of thick‐film OSCs. This review study will be helpful to the researchers engaging in the development of efficient thick‐film OSCs. [ABSTRACT FROM AUTHOR]

Industrial printing production of organic solar cells (OSCs) requires high power conversion efficiency (PCE) with wide toleration of active layer thickness. Herein, high‐efficiency thick‐film OSCs are demonstrated using a polymer fibril network strategy (FNS), which involves a donor polymer (PT2) that can self‐assemble into fibril nanostructure, and two nonfullerene acceptors with different crystalline properties. The fibril network can form a high‐speed hole transport channel and the addition of IDIC as a third component in active layers can improve the electron transport. As a result, the OSCs show high PCEs of ≈12% with wide toleration of active layer thickness (from 100 to 500 nm). The results indicate that FNS is a promising approach for the fabrication of highly efficient thick‐film PSCs, which can facilitate the commercialization of OSCs. [ABSTRACT FROM AUTHOR]

A multitude of studies have been conducted on organic solar cells (OSCs) to understand how end group halogenation changes the property of the small molecular acceptors (SMAs) energetically, morphologically, and so on. But how the halogenation impacts the miscibility between SMAs and polymers, which is an important index to thermodynamically predict and understand the morphology of blend films, has not been systematically studied, particularly for the state‐of‐the‐art polymer–SMA blends. Herein, three series of asymmetric or symmetric SMAs, all reported recently with high photovoltaic performances, are used to investigate the effect of halogenation on miscibility, crystallinity, and solar cell performance. Using the asymmetric SMA named TPIC, and its derivatives (TPIC‐4F and TPIC‐4Cl) as the focus, it is revealed that the enhancement in solar cell performance for the halogenated SMAs is to reduce the miscibility between the acceptor and donor, which leads to a more favorable morphology, enhanced charge transport, and an extended absorption range. Similarly, the halogenation‐induced reduction in miscibility for the initially overmixed donor:acceptor blend is also demonstrated in the symmetric ITIC and the state‐of‐the‐art BTP series, where attractive power conversion efficiencies (PCEs) of 16.5% and 16.8%, respectively, are achieved by the halogenated‐SMA‐based devices in each series. [ABSTRACT FROM AUTHOR]