Chen Weijie

This work develops an ultrafast nucleation process using MACl and BACl as dual additives to 2ME without further solvent addition and the FAPbI₃ PSCs achieve a higher efficiency of 23. 6% with compact and pinhole-free morphology.

Abstract

2-Methoxyethanol (2ME), as a more environmentally friendly solvent with a lower boiling point compared to dimethylformamide, is ideal for the fabrication of perovskite solar cells (PSCs). However, when 2ME is used for antisolvent-free deposition of perovskite films, an uncontrolled nucleation process and an easy phase transition to the δ-phase often occur. Herein, an ultrafast nucleation process is developed using methylamine chloride (MACl) and n-butylammonium chloride (BACl) as dual additives in 2ME without further solvent addition. While MACl can rapidly induce MACl-based nuclei to initiate the nucleation process for formamidinium lead iodide (FAPbI₃), the addition of BACl to the precursor with MACl can further increase the nucleation rate and density of nuclei, and bypass the transition from δ- to α-phase during crystal growth to obtain a highly crystalline and pinhole-free perovskite film. As a result, the FAPbI₃ PSCs achieve a power conversion efficiency (PCE) of 23.6%. This work provides a new inspiration for controlling the crystal quality of perovskite thin films via nucleation rate suitable for upscaling.

Tin(II) oxalate as a substitute for tin(II) fluoride is used to regulate the hot carrier cooling kinetics, increase the carrier diffusion length, and prolong the carrier lifetime. Based on this strategy, the champion efficiencies of mixed Sn-Pb and all-perovskite tandem solar cells are 23.36% and 27.56%, accompanied by significantly improved long-term stability.

Abstract

The rapid relaxation of hot carriers leads to energy loss in the form of heat and consequently restricts the theoretical efficiency of single-junction solar cells; However, this issue has not received much attention in tin-lead perovskites solar cells. Herein, tin(II) oxalate (SnC₂O₄) is introduced into tin-lead perovskite precursor solution to regulate hot-carrier cooling dynamics. The addition of SnC₂O₄ increases the length of carrier diffusion, extends the lifetime of carriers, and simultaneously slows down the cooling rate of carriers. Furthermore, SnC₂O₄ can bond with uncoordinated Sn²⁺ and Pb²⁺ ions to regulate the crystallization of perovskite and enable large grains. The strongly reducing properties of the C₂O₄ ²⁻ can inhibit the oxidation of Sn²⁺ to Sn⁴⁺ and minimize the formation of Sn vacancies in the resulting perovskite films. Additionally, as a substitute for tin(II) fluoride, the introduction of SnC₂O₄ avoids the carrier transport issues caused by the aggregation of F^– ions at the interface. As a result, the SnC₂O₄-treated Sn-Pb cells show a champion efficiency of 23.36%, as well as 27.56% for the all-perovskite tandem solar cells. Moreover, the SnC₂O₄-treated devices show excellent long-term stability. This finding is expected to pave the way toward stable and highly efficient all-perovskite tandem solar cells.

A localized oxidation embellishing (LOE) strategy is introduced by applying (NH₄)₂CrO₄ on SnO₂ electron transport layer in n-i-p structured perovskite solar cells (pero-SCs). The LOE strategy induces plentiful nano-heterojunctions of p-Cr₂O₃/n-SnO₂ on the SnO₂ surface, reducing surface oxygen vacancies and realizing benign energy alignment. The α-FAPbI₃ based pero-SC treated by the LOE strategy achieves power conversion efficiency of 25.72 %.

Abstract

Perovskite solar cell (pero-SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO₂ electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero-SCs, yet still suffers from surface defects of SnO₂ nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH₄)₂CrO₄ on the SnO₂ ETL. The LOE strategy builds up plentiful nano-heterojunctions of p-Cr₂O₃/n-SnO₂ and the nano-heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non-radiative recombination and voltage loss of the pero-SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero-SCs based on α-FAPbI₃ with the SnO₂ ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T₉₀>700 h. This work provides a brand-new view for defect modification of SnO₂ electron transport layer.

A series of A-DA'D-A structured small molecule acceptors (SMAs) with benzotriazole core-based fused ring were synthesized by introducing different N-side chains on the benzotriazole core. The active layers with PM6 as polymer donor and ester side chain SMA BZ-E31 as acceptor show better phase separation morphology and proper domain size. Finally, The PM6 : BZ-E31 based device achieves the highest power conversion efficiency of 18.33 %.

Abstract

Side chain engineering plays a vital role in exploring high-performance small molecule acceptors (SMAs) for organic solar cells (OSCs). In this work, we designed and synthesized a series of A-DA'D-A type SMAs by introducing different N-substituted alkyl and ester alkyl side chains on benzotriazole (BZ) central unit and aimed to investigate the effect of different ester substitution positions on photovoltaic performances. All the new SMAs with ester groups exhibit lower the lowest unoccupied molecular orbital (LUMO) energy levels and more blue-shifted absorption, but relatively higher absorption coefficients than alkyl chain counterpart. After blending with the donor PM6, the ester side chain-based devices demonstrate enhanced charge mobility, reduced amorphous intermixing domain size and long-lived charge transfer state compared to the alkyl chain counterpart, which are beneficial to achieve higher short-circuit current density (J _sc) and fill factor (FF), simultaneously. Thereinto, the PM6 : BZ-E31 based device achieves a higher power conversion efficiency (PCE) of 18.33 %, which is the highest PCE among the OSCs based on the SMAs with BZ-core. Our work demonstrated the strategy of ester substituted side chain is a feasible and effective approach to develop more efficient SMAs for OSCs.

Side-chain random copolymer PMQ-Si605 with a 6,7-difluoro-3-methylquinoxaline-thiophene backbone and 5% siloxane decoration of side chain is synthesized. The polymer with a simple skeleton enables organic solar cells with over 19% efficiency and supplies active layers with processing endurance in high humidity air.

Abstract

Development of polymer donors with simple chemical structure and low cost is of great importance for commercial application of organic solar cells (OSCs). Here, side-chain random copolymer PMQ-Si605 with a simply 6,7-difluoro-3-methylquinoxaline-thiophene backbone and 5% siloxane decoration of side chain is synthesized in comparison with its alternating copolymer PTQ11. Relative to molecular weight (M _n) of 28.3 kg mol⁻¹ for PTQ11, the random copolymer PMQ-Si605 with minor siloxane decoration is beneficial for achieving higher M _n up to 51.1 kg mol⁻¹. In addition, PMQ-Si605 can show stronger aggregation ability and faster charge mobility as well as more efficient exciton dissociation in active layer as revealed by femtosecond transient absorption spectroscopy. With L8-BO-F as acceptor, its PMQ-Si605 based OSCs display power conversion efficiency (PCE) of 18.08%, much higher than 16.21% for PTQ11 based devices. With another acceptor BTP-H2 to optimize the photovoltaic performance of PMQ-Si605, further elevated PCEs of 18.50% and 19.15% can be achieved with the binary and ternary OSCs, respectively. Furthermore, PMQ-Si605 based active layers are suitable for processing in high humidity air, an important factor for massive production of OSCs. Therefore, the siloxane decoration on polymer donors is promising, affording PMQ-Si605 as a high-performing and low cost candidate.

Nature Energy, Published online: 18 January 2024; doi:10.1038/s41560-023-01444-z

Metal halide perovskites (MHPs) are outstanding photovoltaic materials. Nonetheless, despite significant progress, perovskite solar cells (PSCs) still face challenges. It is crucial to adjust the crystallization process during solution crystallization and film formation to overcome this challenge. We primarily discuss the relevant aspects of MHP crystallization kinetics, systematically summarize theoretical methods, and outline modulation techniques for MHP crystallization, including solution engineering, additive engineering, and component engineering.

Abstract

Metal halide perovskites (MHPs) are considered ideal photovoltaic materials due to their variable crystal material composition and excellent photoelectric properties. However, this variability in composition leads to complex crystallization processes in the manufacturing of Metal halide perovskite (MHP) thin films, resulting in reduced crystallinity and subsequent performance loss in the final device. Thus, understanding and controlling the crystallization dynamics of perovskite materials are essential for improving the stability and performance of PSCs (Perovskite Solar Cells). To investigate the impact of crystallization characteristics on the properties of MHP films and identify corresponding modulation strategies, we primarily discuss the relevant aspects of MHP crystallization kinetics, systematically summarize theoretical methods, and outline modulation techniques for MHP crystallization, including solution engineering, additive engineering, and component engineering, which helps highlight the prospects and current challenges in perovskite crystallization kinetics

A facile hydrogen bonding-modulated crystallization strategy is developed to achieve highly-crystalline, uniform, and large-area CsPbI₂Br films, enabling CsPbI₂Br solar cells with record-high efficiencies of 18.14 % and 16.46 % for 0.1 cm² and 1 cm² active area, respectively. The efficiency of 38.24 % under indoor illumination suggests its potential in the applications of powering the Internet of Things, etc.

Abstract

The thermally stable inorganic cesium-based perovskites promise efficient and stable photovoltaics. Unfortunately, the strong ionic bonds lead to uncontrollable rapid crystallization, making it difficult in fabricating large-area black-phase film for photovoltaics. Herein, we developed a facile hydrogen-bonding assisted strategy for modulating the crystallization of CsPbI₂Br to achieve uniform large-area phase-pure films with much-reduced defects. The simple addition of methylamine acetate in precursors not only promotes the formation of intermediate phase via hydrogen bonding to circumvent the direct crystallization of CsPbI₂Br from ionic precursors but also widens the film processing window, thus enabling to fabricate large-area high-quality phase-pure CsPbI₂Br film under benign conditions. Combining with stable dopant-free poly(3-hexylthiophene), the CsPbI₂Br solar cells achieve the record-high efficiencies of 18.14 % and 16.46 % for 0.1 cm² and 1 cm² active area, respectively. The obtained high efficiency of 38.24 % under 1000 lux illumination suggests its potential in indoor photovoltaics for powering the Internet of Things, etc.

Nature Photonics, Published online: 18 January 2024; doi:10.1038/s41566-023-01373-z

Nature, Published online: 17 January 2024; doi:10.1038/s41586-023-06892-x

This article aims to provide a roadmap to guide the development of the optical properties of perovskite/perovskite/silicon triple-junction cells. Thereby, simulations with Sentaurus TCAD are used, calculations with experimental data are validated, and selective measures to improve the power conversion efficiency are provided. The efficiency can be greatly improved by matching the current of the subcells, which can be achieved by the right combination of absorber thicknesses and perovskite bandgaps.

Perovskite-based triple-junction solar cells offer the potential for highly efficient and cost-effective photovoltaic energy conversion. This article aims to provide a roadmap for the optical properties of perovskite/perovskite/silicon triple-junction cells. A comprehensive optoelectrical model for the perovskite/perovskite/silicon structure is developed in Sentaurus TCAD. The optical part of the model is validated by measurements of a triple-junction solar cell. As the electrical characterization is an ongoing process, the electrical properties are assumed to be nonlimiting, which enables us to translate the optical improvement steps into efficiency potentials. A first improvement step lies in adjusting the thicknesses of the perovskite layers to achieve current matching between both perovskite subcells. Using perovskites with bandgaps optimized for planar surfaces, it would be possible to increase the photocurrent density to 13.3 mA cm⁻² and the efficiency to 41.9%. It is shown that by implementing a fully textured structure and using the best available materials, a short-circuit current of 14.1 mA cm⁻² and an open-circuit voltage of 3.48 V with an efficiency of 44.3% are possible assuming idealized electrical properties. This can be regarded as a practical efficiency potential for this kind of triple-junction technology.

Cd0.85PS3Li0.3 was added to active layer to break the trade-off between the crystallinity and phase separation of donor/acceptor, thus boosting the charge transport and power conversion efficiency of heterosystematic organic solar cellsallinity of donor/acceptor (D/A) without influencing the original phase separation, increase the charge transport of the PBDB-T:N2200 device, thus effectively restraining the charge recombination of the device. As a result, the power conversion efficiency (PCE) was boosted from 7.18% to 8.79%, for organic solar cells (OSCs) based on PBDB-T:N2200, from 15.05% to 17.27% for OSCs based on PM6:L8-BO and from 17.29% to 19.10% for OSCs based on D18:L8-BO.

All-polymer solar cells (all-PSCs) demonstrate splendid advantages of thermal and mechanical stability. Nevertheless, the rock-ribbed trade-off between the crystallinity and phase separation scale of donor/acceptor (D/A) hinder the power conversion efficiency (PCE) improvement of all-PSCs. Here, a novel two-dimensional transition-metal phosphorus trichalcogenides (TMPTCs) namely Cd_0.85PS₃Li_0.3 is intelligently designed and synthesized, and firstly employed as a nanoparticle dopant for PBDB-T:N2200-based all-PSCs. The two-dimensional Cd_0.85PS₃Li_0.3 possess enormous surface area that can serve as the nucleation center, inducing the crystallinity of D/A without influencing the original phase separation. Such feature significantly boosted the charge transport, PCE (from 7.18% to 8.79%) and stability of PBDB-T:N2200-based device. Moreover, the Cd_0.85PS₃Li_0.3 nanoparticle dopant was proved to be universal in non-fullerene small molecule acceptor (NFSMA)-based organic solar cells (OSCs), for which the PCE was boosted from 15.05% to 17.27% for PM6:L8-BO-based OSCs and from 17.29% to 19.10% for D18:L8-BO-based OSCs. These observations exemplify the significance of two-dimensional TMPTCs nanoparticle dopant as a tool for breaking the rock-ribbed trade-off between the crystallinity and phase separation scale of D/A in OSCs, which may open up a special field for making two-dimensional TMPTCs work in a unprecedented way in OSCs.

Unfused-ring acceptors with different electron-deficient central cores (quinoxaline (KS40) and benzoxadiazole (KS41) units) lead to higher open-circuit voltages (V _OCs) for organic solar cells, and the KS40-based device achieves a champion power conversion efficiency of 12%.

Unfused-ring acceptors with different electron-deficient central units, dithieno[3,2-f:2′,3′-h]quinoxaline (KS40) and dithieno[3,2-e:2′,3′-g]-2,1,3-benzoxadiazole (KS41) are synthesized and characterized. When blended with PM6, KS40 with a weaker electron-accepting quinoxaline exhibits a much higher open-circuit voltage (V _OC) of 0.945 V. As a result, the KS40-based device achieves a power conversion efficiency (PCE) of 12.2%. PM6:KS41-based devices, in contrast, afford improved charge mobilities as well as suppressed recombination behavior, which eventually leads to an improvement in the fill factor (72.4%). Consequently, the device is able to achieve a PCE of 11.6%.

This work provides an effective two-pronged maneuver for CsPbI_2.75Br_0.25 perovskite films’ inner regulation and surface defects repair simultaneously to improve performance of inorganic perovskite solar cells (IPSCs) without introducing organic materials into final perovskite films. Eventually, the efficiency of CsPbI_2.75Br_0.25 IPSCs is enhanced to 20.75%, the V _OC deficit isreduced to 0.382 V, which is the minimum V _OC deficit of IPSCs.

Despite inorganic perovskites are suitable for application into tandem solar cells, the unsatisfactory crystal quality and inevitable surface defects of low-temperature fabricated inorganic perovskites lead to undesirable open-circuit voltage (V _OC) deficit, which limits the further development of inorganic perovskite solar cells (IPSCs). Herein, dimethylammonium chloride (DMACl) was introduced into perovskite precursor to prolong the solid-state reactions between intermediate phases of DMAPbX₃ and Cs₄PbX₆, and mediate crystallization process of inorganic perovskite, leading to obtain high-quality CsPbI_2.75Br_0.25 perovskite films without DMA⁺ residue in perovskite films after annealing. Additionally, the energy level position of perovskite slightly downshift after adding DMACl, narrowing the band offsets between perovskite and carrier transport layers. To further reduce V _OC deficit and improve the performance of IPSCs, cesium iodide (CsI) thin layer is evaporated onto the perovskite surface to repair inevitable I-related defects. Ultimately, the V _OC and performance of IPSCs are improved without introducing organic components into final perovskite films. A champion photoelectric conversion efficiency of 20.75% is achieved, and the V _OC deficit is significantly decreased to 0.382 V, which is the minimum V _OC deficit of IPSCs at present. Additionally, the stability of the perovskite films and IPSCs has also been remarkably enhanced.

This review provides a thorough examination of the shift towards eco-friendly solvents in the fabrication of Perovskite Solar Cells (PSC), shedding light on the challenges and opportunities accompanying this crucial move towards a more environmentally sustainable approach to renewable energy production.

The shift towards ecofriendly solvents in perovskite solar cell (PSC) production represents a significant leap towards sustainable renewable energy generation, effectively addressing concerns related to the harmful nature of conventional solvents employed in PSC manufacturing. This review assesses the toxicity of traditional solvents utilized in the PSC fabrication process as well as recent studies and challenges related to substituting toxic solvents with less harmful or green alternatives. Although considerable efforts have been made to adopt greener solvents, this review underscores the variations in evaluations based on specific criteria, highlighting the need for thorough consideration to ensure the viability and sustainability of each solvent replacement. This study offers a comprehensive exploration of the transition to greener solvents in PSC fabrication and elucidates the associated challenges and opportunities in this pivotal shift towards a more environmentally sustainable approach to renewable energy production.

As a pivotal component within solar devices, the electrode has a profound impact on the device performance. Herein, device configuration based on the physically and chemically stable molybdenum electrode is engineered to fundamentally tackle the instability factors introduced by electrodes in perovskite solar cells. A titanium seed layer is further introduced to optimize the electrode interfacial contact.

Abstract

Metal halide perovskite solar cells (PSCs) have garnered much attention in recent years. Despite the remarkable advancements in PSCs utilizing traditional metal electrodes, challenges such as stability concerns and elevated costs have necessitated the exploration of innovative electrode designs to facilitate industrial commercialization. Herein, a physically and chemically stable molybdenum (Mo) electrode is developed to fundamentally tackle the instability factors introduced by electrodes. The combined spatially resolved element analyses and theoretical study demonstrate the high diffusion barrier of Mo ions within the device. Structural and morphology characterization also reveals the negligible plastic deformation and halide-metal reaction during aging when Mo is in contact with perovskite (PVSK). The electrode/underlayer junction is further stabilized by a thin seed layer of titanium (Ti) to improve Mo film's uniformity and adhesion. Based on a corresponding p–i–n PSCs (ITO/PTAA/PVSK/C₆₀/SnO₂/ITO/Ti/Mo), the champion sample could deliver an efficiency of 22.25%, which is among the highest value for PSCs based on Mo electrodes. Meanwhile, the device shows negligible performance decay after 2000 h operation, and retains 91% of the initial value after 1300 h at 50–60 °C. In summary, the multilayer Mo electrode opens an effective avenue to all-round stable electrode design in high-performance PSCs.

An amino-functionalized graphdiyne derivative (GDY-N), with its high conductivity, appropriate LUMO energy level, and good solubility in alcohols, emerges as a remarkable cathode interlayer material. An impressive power conversion efficiency (PCE) of 19.30% is achieved for D18-Cl:L8-BO-based devices (certified result: 19.05%). This value is one of the highest reported for OSCs to date.

Abstract

Efficient cathode interfacial materials (CIMs) are essential components for effectively enhancing the performance of organic solar cells (OSCs). Although high-performance CIMs are desired to meet the requirements of various OSCs, potential candidates for CIMs are scarce. Herein, an amino-functionalized graphdiyne derivative (GDY-N) is developed, which represents the first example of GDY that exhibits favorable solubility in alcohol. Utilizing GDY-N as the CIM, an outstanding champion PCE of 19.30% for devices based on the D18-Cl:L8-BO (certified result: 19.05%) is achieved, which is among the highest efficiencies reported to date in OSCs. Remarkably, the devices based on GDY-N exhibit a thickness-insensitive characteristic, maintaining 95% of their initial efficiency even with a film thickness of 25 nm. Moreover, the GDY-N displays wide universality and facilitates exceptional stability in OSCs. This work not only enriches the diversity of GDY derivatives, but also demonstrates the feasibility of GDY derivatives as CIMs with high thickness tolerance in OSCs.

A facile approach to reduce the crystallinity difference between donor and acceptor has been proposed by incorporating a novel liquid crystal small molecule, BDTPF4-C6, which balances charge transport and suppresses charge recombination in organic solar cells. Intriguingly, dual Förster resonance energy transfer was firstly observed between guest molecule and host donor and acceptor, resulting in increased charge generation in ternary blend.

Abstract

Achieving a more balanced charge transport by morphological control is crucial in reducing bimolecular and trap-assisted recombination and enhancing the critical parameters for efficient organic solar cells (OSCs). Hence, a facile strategy is proposed to reduce the crystallinity difference between donor and acceptor by incorporating a novel multifunctional liquid crystal small molecule (LCSM) BDTPF4-C6 into the binary blend. BDTPF4-C6 is the first LCSM based on a tetrafluorobenzene unit and features a low liquid crystal phase transition temperature and strong self-assembly ability, conducive to regulating the active layer morphology. When BDTPF4-C6 is introduced as a guest molecule into the PM6 : Y6 binary, it exhibits better compatibility with the donor PM6 and primarily resides within the PM6 phase because of the similarity-intermiscibility principle. Moreover, systematic studies revealed that BDTPF4-C6 could be used as a seeding agent for PM6 to enhance its crystallinity, thereby forming a more balanced and favourable charge transport with suppressed charge recombination. Intriguingly, dual Förster resonance energy transfer was observed between the guest molecule and the host donor and acceptor, resulting in an improved current density. This study demonstrates a facile approach to balance the charge mobilities and offers new insights into boosting the efficiency of single-junction OSCs beyond 20 %.

PSCs are prepared by doping choline chloride (CC), acetylcholine chloride (AC), phosphocholine chloride sodium salt (PCSS) into SnO₂ dispersion. These dopants can act as bridge through synergistic effects to form uniform ETL morphology, enhance the interface contact, and passivate defects. Ultimately, the device with SnO₂-PCSS ETL achieves a champion PCE of 23.06% and an ideal voltage of 1.2 V.

Abstract

The interfacial carrier non-radiative recombination caused by buried defects in electron transport layer (ETL) material and the energy barrier severely hinders further improvement in efficiency and stability of perovskite solar cells (PSCs). In this study, the effect of the SnO₂ ETL doped with choline chloride (CC), acetylcholine chloride (AC), and phosphocholine chloride sodium salt (PCSS) are investigated. These dopants modify the interface between SnO₂ ETL and perovskite layer, acting as a bridge through synergistic effects to form uniform ETL films, enhance the interface contact, and passivate defects. Ultimately, compared with CC (which with ─OH) and AC (which with C═O), the PCSS with P═O and sodium ions groups is more beneficial for improving performance. The device based on PCSS-doped SnO₂ ETL achieves an efficiency of 23.06% with a high V_OC of 1.2 V, which is considerably higher than the control device (20.55%). Moreover, after aging for 500 h at a temperature of 25 °C and relative humidity (RH) of 30–40%, the unsealed device based on SnO₂-PCSS ETL maintains 94% of its initial efficiency, while the control device only 80%. This study provides a meaningful reference for the design and selection of ideal pre-buried additive molecules.

A halogenation strategy of thiophene-derived solvent additives is developed to optimize blend morphologies of organic solar cells (OSCs). The resulting binary (PM6:L8-BO) and ternary (PM6:L8-BO:BTP-eC9) OSCs achieve both superior efficiencies of 18.29% and 19.17%, in which 19.17% efficiency is as one of the top values so far.

Abstract

As simple and versatile tools, additives have been widely used to refine active layer morphology and have played a crucial role in boosting the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, three novel solvent additives named Th-FSi, Th-ClSi, and Th-BrSi with the same backbone of 2,5-bis(trimethylsilyl)thiophene are designed and synthesized by substituting different halogens of fluorine, chlorine, and bromine, respectively. Notably, Th-ClSi exhibits the more significant dipole moment and engages in non-covalent interactions with a small-molecule acceptor (SMA) L8-BO, which slight adjustments in intermolecular interaction, crystallinity, and molecular packing in the PM6:L8-BO active layer. Consequently, the OSCs incorporating Th-ClSi outperform their Th-FSi and Th-BrSi counterparts in photo-capturing, reduced energy loss, superior exciton dissociation, and charge transfer properties, out-coming yields in an enhanced PCE of 18.29%. Moreover, by integrating a near-infrared absorbing SMA (BTP-eC9) guest into the PM6:L8-BO matrix, the absorption spectrum to span 880–930 nm, and the resultant ternary OSCs achieve a commendable PCE of 19.17%, ranking among the highest efficiencies reported to date is expanded. These findings underscore the promise of halogenated thiophene-based solvent additives as a potent avenue for morphological fine-tuning and consequent PCE enhancement in OSCs.

A benzothiophene-based SAM HSLMeO-BTBT is developed. Compared to the carbazole-based MeO-2PACz SAM, MeO-BTBT shows stronger intermolecular interactions, a passivation effect at the buried interface, and better photo-stability, enabling a robust HSL and stable perovskite bottom interface morphology. The devices with the MeO-BTBT HSL achieves a PCE of 24.53% with excellent long-term device stability under illumination and thermal stress.

Abstract

Effective passivation of defects at the buried interface between the perovskite absorber and hole-selective layer (HSL) is crucial for achieving high performance in inverted perovskite solar cells (PSCs). Additionally, the HSL needs to possess compact molecular packing and intrinsic photo- and thermo-stability to ensure long-term operation of the devices. In this study, a novel MeO-BTBT-based self-assembled monolayer (SAM) is reported to serve as an efficient HSL in inverted PSCs. Compared to the well-established carbazole-containing SAM MeO-2PACz, MeO-BTBT has flat and more extended conjugation with large atomic radius of the sulfur atom. These induce stronger intermolecular interactions to enable more ordered and compact SAM to be formed on indium–tin oxide (ITO) substrates. Meanwhile, the sulfur atoms in MeO-BTBT can coordinate with Pb²⁺ ions to passivate the defects at the buried interface of perovskite absorber. The derived perovskite films show both high photoluminescence (PL) quantum yield (13.2%) and a long lifetime (7.2 µs). The PSCs based on MeO-BTBT show a PCE of 24.53% with an impressive fill factor of 85.3%. The PCEs of MeO-BTBT-based devices can maintain ≈95% of their initial values after being aged at 65 °C for more than 1000 h or continuous operation under 1-sun illumination.

This review first introduces the current status of perovskite solar cells (PSCs) and modules and their potential applications. Then it identifies critical challenges in commercialization and corresponding solutions, including strategies for power conversion efficiency (PCE) enhancement over large areas, stability improvements, toxicity reduction, and so on. Finally, it includes some potential development directions and issues requiring attention in the future.

Abstract

Perovskite (PVSK) photovoltaic (PV) devices are undergoing rapid development and have reached a certified power conversion efficiency (PCE) of 26.1% at the cell level. Tremendous efforts in material and device engineering have also increased moisture, heat, and light-related stability. Moreover, the solution-process nature makes the fabrication process of perovskite photovoltaic devices feasible and compatible with some mature high-volume manufacturing techniques. All these features render perovskite solar modules (PSMs) suitable for terawatt-scale energy production with a low levelized cost of electricity (LCOE). In this review, the current status of perovskite solar cells (PSCs) and modules and their potential applications are first introduced. Then critical challenges are identified in their commercialization and propose the corresponding solutions, including developing strategies to realize high-quality films over a large area to further improve power conversion efficiency and stability to meet the commercial demands. Finally, some potential development directions and issues requiring attention in the future, mainly focusing on further dealing with toxicity and recycling of the whole device, and the attainment of highly efficient perovskite-based tandem modules, which can reduce the environmental impact and accelerate the LCOE reduction are put forwarded.

A 3D Y-branched regio-regular polymerized small-molecule acceptor PYBF is synthesized, which exhibits more crystalline and face-on-oriented domains. 1D PYIT is further introduced into the PM6:PYBF system for forming the interconnective neuron-like dual-acceptor domains. Consequently, the device realizes a best power conversion efficiency of ≈17% with simultaneously enhanced stabilities.

Abstract

All-polymer solar cells have garnered particular attention thanks to their superior thermal, photo, and mechanical stabilities for large-scale manufacturing, yet the performance enhancement remains largely restrained by inherent morphological challenges of the bulk-heterojunction active layer. Herein, a 3D Y-branched polymerized small-molecule acceptor named PYBF, characteristic of high molecular weight and glass transition temperature, is designed and synthesized by precisely linking C _3h-symmetric benzotrifuran with Y6 acceptors. In comparison to the benchmark thiophene-bridged linear PYIT acceptor, an optical blue-shift absorption is observed for PYBF yet a slightly higher power conversion efficiency (PCE) of 15.7% (vs 15.14%) is obtained when paired with polymer donor PM6, which benefit from the more crystalline and face-on-oriented PYBF domains. However, the star-like bulky structure of PYBF results in the nucleation-growth dominant phase-separation in polymeric blends, which generates stumpy droplet-like acceptor fibrils and impairs the continuity of acceptor phases. This issue is however surprisingly resolved by incorporating a small amount of PYIT, which leads to the formation of the more interconnective neuron-like dual-acceptor domains by long-chain entanglements of linear acceptors and alleviates bimolecular recombination. Thus, the champion device realizes a respectable PCE of up to ≈17% and importantly exhibits thermal and storage stabilities superior to the linear counterpart.

Publication date: April 2024

Source: Nano Energy, Volume 122

Author(s): Li-Rong Zeng, Bin Ding, Gao Zhang, Yan Liu, Xin Zhang, Guan-Jun Yang, Bo Chen

Cost-effective organic solar cells (OSCs) with low-cost materials and high-performance are critical to commercialization. Herein, based on synthesized easily cyanoesterthiophene group and easy-adjusting random terpolymerization, a new polymer donor with 17.14% efficiency is reported, which is fully comparable with the currently polymer donor. This study not only reveals the impact of copolymerization and blending strategies on performance, but also provides valuable insights into applications in practical production.

Abstract

To achieve commercial application of organic solar cells (OSCs), it is necessary to reduce material costs and improve device efficiency. This paper reports on the utilization of a multifunctional building block, namely 3-cyanoesterthiophene, which exhibits simple structure and accessibility of synthetic for cost-effective and high-performance polymer donors (PDs). Meanwhile, ternary and terpolymerization strategies have been studied. Two similar PDs, PBTCl0-TCA and PBTCl100-TCA, are synthesized, and the devices exhibit less-than-satisfactory efficiency of 13.21% and 11.53% due to mismatching energy level and imperfect morphology. The two PDs with comparable structures and commendable compatibility easily form alloy-like phase in active layer, which can effectively boost the efficiency of ternary devices to 14.17% with retained high J _SC and significant improved open-circuit voltage (V _OC) and fill factor (FF). Encouraged by the ternary blending phenomenon, a polymer donor (PBTCl50-TCA) with same ratio by random terpolymerization is designed. And over 17% efficiency binary OSCs using terpolymerization donor are demonstrated. The synergies of incorporation of the cyanoester-group and terpolymer endow the developed PDs with deep-lying energy levels, face-on orientation, thermodynamic miscibility with the prevailing nonfullerene acceptor and appropriate polymer crystallinity. The findings study provide valuable insights and support for the advancement of cost-effective and high-performance PDs.

Nature Energy, Published online: 12 January 2024; doi:10.1038/s41560-023-01441-2

Nature Energy, Published online: 12 January 2024; doi:10.1038/s41560-023-01442-1