Publication date: 19 August 2020
Source: Joule, Volume 4, Issue 8
Author(s): Lingeswaran Arunagiri, Zhengxing Peng, Xinhui Zou, Han Yu, Guangye Zhang, Zhen Wang, Joshua Yuk Lin Lai, Jianquan Zhang, Yan Zheng, Chaohua Cui, Fei Huang, Yingping Zou, Kam Sing Wong, Philip C.Y. Chow, Harald Ade, He Yan
Hybridization between the charge transfer (CT) state of a donor‐acceptor pair and lowest exciton state of the donor or the acceptor is reported to be effective for reducing recombination loss in organic photovoltaic (OPV) devices. While this approach shows a great success in maximizing open circuit voltage (Voc), it is typically accompanied with low device performance. Here, we report “complete boron sub‐(na)phthalocyanine devices” with strong hybridization resulting in lower recombination loss (∽0.47 eV) while not penalizing charge separation dynamics (internal quantum efficiency (IQE)>80% and fill factor (FF)>70%). Interestingly, when boron sub‐(na)phthalocyanine is paired with any other active material used in this study (“partial boron sub‐(na)phthalocyanine device”), recombination losses are still consistently maintained at lower levels (<0.53 eV). These observations denote the capability of boron sub‐(na)phthalocyanine to result in lower recombination loss devices while pairing with other materials. Special intrinsic characteristics of these materials (high dielectric constant, sharp absorption edge, unusually high absorption coefficient) and hybridization collectively result in reduced recombination loss and efficient charge generation in these systems.
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A low‐temperature crystallization strategy of CsPbIBr2 perovskite solar cells is reported. The additive n‐butylammonium iodide (BAI) is incorporated into the perovskite precursor to improve crystallinity, optimize morphology, and passivate defects at 160 °C. As a result, a high‐level PCE of 10.78% with a high open‐circuit voltage (V OC) of 1.25 V is achieved.
Inorganic cesium lead halide perovskite solar cells (PSCs) have been widely explored due to their outstanding thermal stability and photovoltaic performance. However, the application and development of CsPbIBr2‐based PSCs is still hindered by major challenges such as high fabrication temperature and large voltage loss. To address these difficulties, additive engineering is conducted using n‐butylammonium iodide (BAI). It is found that it not only improves the crystallization and morphology of perovskite layers but also substantially decreases the annealing temperature. In addition, the BAI incorporation decreases trap state density and restrains nonradiative recombination. As such, a high power conversion efficiency (PCE) of 10.78% is achieved, 21% higher compared with that of the control sample (8.88%). It should be noted that this is particularly high for the CsPbIBr2 PSCs fabricated at low temperatures (<200 °C) that are required for flexible devices based on polymeric substrates.
Organic solar cells (OSCs) are promising photovoltaic devices due to ease of synthesis, the abundance of materials, low cost, and efficiencies up to 17% have been achieved to date. Conventionally, spin coating is used for the OSC fabrication process. However, the spin coating does not allow control at the atomic‐scale, which is required for reaching the full potential of OSCs. Zinc oxide (ZnO) is a commonly used electron transport layer (ETL) in OSCs, and this layer is currently limiting its efficiency potential. In this work, we show for the first time that atomic layer deposition (ALD), which allows for controlled thin film growth with atomic‐scale control in thickness and composition, can effectively be used to optimise the ETL for non‐fullerene OSCs. First, we discuss density functional theory (DFT) calculations to show the impact of doping ZnO with zirconium (Zr) on its density of states. Zr has a similar ionic size as Zn and donates two electrons to the conduction band when substitutionally integrated into ZnO, and the DFT calculations confirm that Zr doping of ZnO results in a degenerated semiconductor. Subsequently, we detail the synthesis of Zr doped ZnO films by ALD using a supercycle approach and report the compositional and optoelectronic material properties in detail. A 2.4% Zr concentration is found to be optimal in terms of optoelectronic properties and sufficiently low defect density. This film is used as an ETL in a non‐fullerene based OSC with an inverted structure of ITO/ETL/PM6:N3/MoO3/Ag. The device with the Zr‐doped ZnO layer shows a better performance than the device with an un‐doped ZnO ETL. The champion efficiency of an OSC with the Zr‐doped ETL is 14.7%, a record for this design and an increase of ∽1% absolute compared to a device with the undoped ZnO ETL. This improvement is attributed to lower series resistance, a suppressed surface recombination, and an enhanced current extraction resulting from the Zr‐doped ZnO. This work demonstrates the potential of atomic‐scale engineering afforded by ALD towards achieving the ultimate efficiency of OSCs.
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WS2 flakes are introduced as a template for van der Waals epitaxial growth of mixed perovskite films along (001) in perovskite solar cells with an inverted structure. Moreover, the WS2 interlayer forms a cascade energy alignment in the devices, which favors charge extraction and reduces interfacial recombination. The devices exhibit a power conversion efficiency up to 21.1% along with excellent stability.
Organic–inorganic metal halide perovskite solar cells (PSCs) have attracted much research interest owing to their high power conversion efficiency (PCE), solution processability, and the great potential for commercialization. However, the device performance is closely related to the quality of the perovskite film and the interface properties, which cannot be easily controlled by solution processes. Here, 2D WS2 flakes with defect‐free surfaces are introduced as a template for van der Waals epitaxial growth of mixed perovskite films by solution process for the first time. The mixed perovskite films demonstrate a preferable growth along (001) direction on WS2 surfaces. In addition, the WS2/perovskite heterojunction forms a cascade energy alignment for efficient charge extraction and reduced interfacial recombination. The inverted PSCs with WS2 interlayers show high PCEs up to 21.1%, which is among the highest efficiency of inverted planar PSCs. This work demonstrates that high‐mobility 2D materials can find important applications in PSCs as well as other perovskite‐based optoelectronic devices.
Publication date: November 2020
Source: Nano Energy, Volume 77
Author(s): Junsheng Luo, Jianxing Xia, Hua Yang, Chunlin Sun, Ning Li, Haseeb Ashraf Malik, Hongyu Shu, Zhongquan Wan, Haoli Zhang, Christoph J. Brabec, Chunyang Jia
Publication date: November 2020
Source: Nano Energy, Volume 77
Author(s): Qian-Qian Chu, Zhijian Sun, Bin Ding, Kyoung-sik Moon, Guan-Jun Yang, Ching-Ping Wong
Publication date: 19 August 2020
Source: Joule, Volume 4, Issue 8
Author(s): Ening Gu, Xiaofeng Tang, Stefan Langner, Patrick Duchstein, Yicheng Zhao, Ievgen Levchuk, Violetta Kalancha, Tobias Stubhan, Jens Hauch, Hans Joachim Egelhaaf, Dirk Zahn, Andres Osvet, Christoph J. Brabec
Zr doping of a ZnO electron transport layer increases the efficiency of organic solar cells (OSCs) by 1% absolute. The OSC results are supported by detailed density functional theory and material studies of atomic‐layer‐deposited Zr‐doped ZnO films.
Organic solar cells (OSCs) are promising photovoltaic devices and zinc oxide (ZnO) is a commonly used electron transport layer (ETL) in OSCs. However, the conventional spin‐coating ZnO layer is currently limiting its efficiency potential. Herein, it is shown for the first time that atomic layer deposition (ALD), which allows for controlled thin film growth with atomic‐scale control, can effectively be used to optimize the ZnO for nonfullerene OSCs. First, density functional theory (DFT) calculations are discussed to show the impact of doping ZnO with zirconium (Zr) on its density of states and detail the synthesis of Zr doped ZnO films by ALD using a supercycle approach. A 2.4% Zr concentration is found to be optimal in terms of optoelectronic properties and sufficiently low defect density. The champion efficiency of 14.7% for a PM6:N3‐based nonfullerene OSC with Zr‐doped ZnO ETL are obtained, which is ≈1% absolute higher compared to a device with an undoped ZnO ETL. This improvement is attributed to a lower series resistance, a suppressed surface recombination, and an enhanced current extraction resulting from the Zr‐doped ZnO. This work demonstrates the potential of atomic‐scale engineering afforded by ALD towards achieving the ultimate efficiency of OSCs.
Herein, an ink‐composition engineering approach for high‐performing flexible slot‐die‐coated indium tin oxide (ITO)‐free organic solar cells is presented. Optimized large‐area devices (0.88 cm2) show a power conversion efficiency of up to 10.21%, which is an efficiency retention factor of 0.86 when compared to optimized small‐area spin‐coated devices.
The potential for commercialization of organic solar cells (OSCs) has vastly increased in recent years as the device efficiency for small‐scale laboratory OSCs has continuously increased. There are, however, still multiple challenges that need to be addressed and overcome. Among them, upscaling of the device manufacturing techniques to be compatible with the potential attributes of low cost must be the pinnacle. Herein, a pathway for upscaling with an ink‐engineering approach toward in‐air optimization of large‐area OSCs is presented. Optimized flexible indium tin oxide (ITO)‐free OSCs based on a PTB7‐TH:IEICO‐4F:PC71BM ternary blend show efficiencies up to 10.2% (device active area 0.88 cm2), which is the highest value reported to date (for in‐air slot‐die‐coated devices). This is achieved through ink modifications and optimizations as well as electrode and active layer compositional optimizations, leading to an impressive efficiency retention of 0.86 compared to the in‐literature optimized small‐scale devices.
A new ethanol‐soluble ionic fullerene derivative, C60RT6, is synthesized to be an additive of ground TiO2 nanoparticles (NPs) for preparing a room‐temperature‐processed nanocomposite electron transporting layer (ETL) (R‐Fu/Lt‐TiO2) to improve the photovoltaic performance of the corresponding planar regular perovskite solar cell (PSC). Rigid and flexible PSC–based R‐Fu/Lt‐TiO2 achieves the power conversion efficiency of 20% and 16.2%, respectively.
Room‐temperature‐processed TiO2 (R‐Lt‐TiO2) electron transporting layers (ETLs) possess low conductivity and connectivity, resulting in poor photovoltaic performance. Herein, an ethanol (EtOH)‐soluble, highly conducting fullerene derivative, C60RT6, was used as an additive for Lt‐TiO2 ETLs. Room‐temperature processed nanocomposite ETL (R‐Fu/Lt‐TiO2) is prepared simply by spin coating a C60RT6 and G‐TiO2 NPs (TiO2 nanoparticle prepared by grinding the bulk TiO2 powder) mixture. R‐Fu/Lt‐TiO2 has better aligned with the frontier orbitals of the FAxMA1−xPbI3, better continuity, conductivity, flatness, and higher surface hydrophilicity compared to Lt‐TiO2 ETL. Perovskite films spin coated on R‐Fu/Lt‐TiO2 ETLs also have slightly larger grains and thickness compared to those deposited on Lt‐TiO2. Perovskite solar cells (PSCs) based on a R‐Fu/Lt‐TiO2 ETL possess higher power conversion efficiency (PCE, up to 20% on glass substrate), less (negligible) current hysteresis, and better long‐term stability compared to those using R‐Lt‐TiO2 as an ETL. The flexible PSC (used indium tin oxide/polyethylene terephthalate (ITO/PET) as a substrate) with a R‐Fu/Lt‐TiO2 ETL achieves a PCE of 18.06% and retains 90% of the initial PCE after 500 bending cycles with a bending radius of 6 mm. The PCE of the flexible cell with a Lt‐TiO2 ETL is only 8.2%, and loses 60% of the initial value after 500 bending cycles.
A simple and effective sulfur‐doping method–based chemical bath deposition is introduced to improve interface contact between NiO and perovskite for efficient inverted perovskite solar cells. Sulfur doping leads to promoted perovskite film quality with reduced amount of grain boundaries and trap‐assisted charge recombination. The champion efficiency based on MAPbI3 reaches 20.43% in the NiO‐based inverted photovoltaic (PV) device.
As one of the most promising hole‐transporting materials for perovskite solar cells (PSC), NiO is widely used in the inverted p–i–n cell structure due to its high stability, decent hole conductivity, and easy processability for hysteresis‐free cells. However, the efficiency of NiO‐based PSCs is still low, due largely to the poor perovskite/NiO interface. Herein, a sulfur‐doping strategy to modify NiO surface via ion exchange reaction by a simple and scalable chemical bath deposition technique is introduced, which greatly improves the photovoltaic (PV) performance of the derived devices. A systematic investigation is shown where sulfur doping leads to favorable interfacial energetics with a reduced V oc loss. Sulfur doping at the interface also improves the contact between NiO and perovksite and facilitates the formation of high‐quality perovskite films. Carrier dynamics studies demonstrate reduced defect states and trap‐assisted recombination with sulfur doping, which promote the PV performance of the devices. These merits contribute concurrently to low‐loss charge transfer across the perovskite/NiO interface and facilitate charge transport through the perovskite films, leading to a high champion efficiency of 20.43% of the p–i–n structure solar cell devices.
Grazing incidence small‐ and wide‐angle X‐ray scattering (GISAXS and GIWAXS) are extensively used for the characterization of film morphology of organic solar cells (OSCs). Herein, the use of these techniques to find the effect of chemistry of active layer materials and different pre‐ and postprocessing conditions on the film morphology of OSCs is discussed.
In recent years, a rapid evolution of organic solar cells (OSCs) has been achieved by virtue of structural design of active layer materials and optimization of film morphology. Along with other characterization techniques, grazing incidence small‐ and wide‐angle X‐ray scattering (GISAXS and GIWAXS) have played significant role in deeper understanding of film morphology. Herein, the importance of these techniques is explained with examples from various aspects of OSCs. Different pre‐ and post‐processing conditions such as solvent effect, solvent additive, solvent, and thermal annealing are studied in the framework of these techniques. Moreover, the impact of donor:acceptor ratio and molecular weight of semiconductor on microstructure is also explored. Finally, the effect of chemical structure of organic semiconductors (both polymers and small molecules) on the film morphology is discussed. These techniques provide valuable information about crystallinity, phase separation, and domain size of nanostructured film morphology, which helps to optimize the film morphology and enhances the performance of OSCs. The role of these techniques will become more important as the mystery of film morphology still has to be solved.
An efficient non‐conjugated polymer acceptor PF1‐TS4 was developed by embedding thioalkyl linkages in the mainchain of a conjugated polymer. The resulting all‐polymer solar cells achieved a promising device efficiency of 8.63 % with excellent thermal stability at 85 °C for 180 hours.
A non‐conjugated polymer acceptor PF1‐TS4 was firstly synthesized by embedding a thioalkyl segment in the mainchain, which shows excellent photophysical properties on par with a fully conjugated polymer, with a low optical band gap of 1.58 eV and a high absorption coefficient >105 cm−1, a high LUMO level of −3.89 eV, and suitable crystallinity. Matched with the polymer donor PM6, the PF1‐TS4‐based all‐PSC achieved a power conversion efficiency (PCE) of 8.63 %, which is ≈45 % higher than that of a device based on the small molecule acceptor counterpart IDIC16. Moreover, the PF1‐TS4‐based all‐PSC has good thermal stability with ≈70 % of its initial PCE retained after being stored at 85 °C for 180 h, while the IDIC16‐based device only retained ≈50 % of its initial PCE when stored at 85 °C for only 18 h. Our work provides a new strategy to develop efficient polymer acceptor materials by linkage of conjugated units with non‐conjugated thioalkyl segments.
1,3‐dimethyl‐2‐(thiophen‐2‐yl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (DMBI‐2‐Th) and its iodine ionized molecule DMBI‐2‐Th‐I are developed to regulate the electronic states of bulk perovskite for efficient p–i–n pero‐SCs, leading to a significant improvement in electron trap density, electron concentration, ambipolar charge transporting property, and electronic extraction efficiency. Finally, a promising power conversion efficiency of 20.90% with excellent moisture stability is obtained.
The power conversion efficiency (PCE) of planar p–i–n perovskite solar cells (pero‐SCs) is commonly lower than that of the n–i–p pero‐SCs, due to the severe nonradiative recombination stemming from the more p‐type perovskite with prevailing electron traps. Here, two n‐type organic molecules, DMBI‐2‐Th and DMBI‐2‐Th‐I, with hydrogen‐transfer properties for the doping of bulk perovskite aimed at regulating its electronic states are synthesized. The generated radicals in these n‐type dopants with high‐lying singly occupied molecular orbitals enable easy transfer of the thermally activated electrons to the MAPbI3 perovskite for the realization of n‐doped perovskites. The n‐doping degree could be further enhanced by using the iodine ionized dopant DMBI‐2‐Th‐I. The doping effect could reduce the electron trap density, increase the electron concentration of the bulk perovskite, and simultaneously improve the surface electronic contact. When the DMBI‐2‐Th‐I‐doped perovskite is used in planar p–i–n pero‐SCs, the nonradiative recombination is significantly suppressed. As a result, the photovoltaic performance improved significantly, as evidenced by an excellent PCE of 20.90% and a robust ambient stability even under high relative humidity. To the best of the knowledge, this work represents the first example where organic n‐type dopants are used to tune the electronic states of a bulk perovskite film for efficient planar p–i–n pero‐SCs.
Soft routed benzimidazole clubbed phenoxazine‐based organic ionic plastic crystals with iodide and bromide anions successfully introduced as hole transporting materials in perovskite solar cells yield power conversion efficiencies exceeding 18%, which represents the best alternative to existing spiro‐OMeTAD due to high conductivity and hole mobility with a safer, stable, and efficient system.
Organic ionic plastic crystals (OIPCs) are synthesized through a simple metal‐free, cost‐effective approach. The strategized synchronization of electron‐rich phenoxazine with benzimidazolium iodide (OIPC‐I) and bromide (OIPC‐Br) salts lead to enhanced hole mobility and conductivity of OIPCs which is suitable for an efficient alternative to conventional organic hole transporting materials (HTMs) for stable perovskite solar cells (PSCs). The fabricated PSCs with OIPC‐I as hole transporting layer yielded a power conversion efficiency of 15.0% and 18.1% without and with additive (Li salt) respectively, which are comparable with spiro‐OMeTAD based devices prepared under similar conditions. Furthermore, the PSCs with OIPCs show good stability compared to the spiro‐OMeTAD with or without additives. Here, first time benzimidazolium‐based OIPCs have been used as an alternative organic HTM for perovskite solar cells, which opens a window for the design of effective OIPCs for highly efficient PSCs with long‐term stability.
A well‐designed inorganic–organic double hole transporting layer (HTL) based on inorganic CuSCN and organic polymer dithiophene‐benzene is developed. A perovskite solar cell with this dopant‐free HTL exhibits a very high power conversion efficiency of 22.0% (certified: 21.7%) and significantly improved thermal, humidity, and light stabilities compared to 2,2′,7,7′‐tetrakis(N ,N‐di‐p‐methoxyphenylamine)‐9,9‐spirobifluorene (Spiro‐OMeTAD) HTL‐based devices.
Most of the high performance in perovskite solar cells (PSCs) have only been achieved with two organic hole transporting materials: 2,2′,7,7′‐tetrakis(N ,N‐di‐p‐methoxyphenylamine)‐9,9‐spirobifluorene (Spiro‐OMeTAD) and poly(triarylamine) (PTAA), but their high cost and low stability caused by the hygroscopic dopant greatly hinder the commercialization of PSCs. One effective alternative to address this problem is to utilize inexpensive inorganic hole transporting layer (i‐HTL), but obtaining high efficiency via i‐HTLs has remained a challenge. Herein, a well‐designed inorganic–organic double HTL is constructed by introducing an ultrathin polymer layer dithiophene‐benzene (DTB) between CuSCN and Au contact. This strategy not only enhances the hole extraction efficiency through the formation of cascaded energy levels, but also prevents the degradation of CuSCN caused by the reaction between CuSCN and Au electrode. Furthermore, the CuSCN layer also promotes the formation of a pinhole‐free and compact DTB over layer in the CuSCN/DTB structure. Consequently, the PSCs fabricated with this CuSCN/DTB layer achieves the power conversion efficiency of 22.0% (certified: 21.7%), which is among the top efficiencies for PSCs based on dopant‐free HTLs. Moreover, the fabricated PSCs exhibit high light stability under more than 1000 h of light illumination and excellent environmental stability at high temperature (85 °C) or high relative humidity (>60% RH).
A carbon nanotube ink is developed that can be spin coated directly onto a silicon wafer and which serves as a hole extraction layer but also to passivate interfacial defects. Power conversion efficiencies of 21.4% on a device area of 4.8 cm2 and 20% on an industrial size (245.71 cm2) wafer are obtained.
Traditional silicon solar cells extract holes and achieve interface passivation with the use of a boron dopant and dielectric thin films such as silicon oxide or hydrogenated amorphous silicon. Without these two key components, few technologies have realized power conversion efficiencies above 20%. Here, a carbon nanotube ink is spin coated directly onto a silicon wafer to serve simultaneously as a hole extraction layer, but also to passivate interfacial defects. This enables a low‐cost fabrication process that is absent of vacuum equipment and high‐temperatures. Power conversion efficiencies of 21.4% on an device area of 4.8 cm2 and 20% on an industrial size (245.71 cm2) wafer are obtained. Additionally, the high quality of this passivated carrier selective contact affords a fill factor of 82%, which is a record for silicon solar cells with dopant‐free contacts. The combination of low‐dimensional materials with an organic passivation is a new strategy to high performance photovoltaics.
The recent progress of flexible and stretchable organic solar cells (OSCs) is discussed. For flexible OSCs, the features of the commonly used flexible transparent electrodes and the relevant performance are selectively summarized and discussed. For stretchable OSCs, both the nonintrinsic and intrinsic processing methods are presented and discussed.
Flexible and stretchable organic solar cells (OSCs) have attracted enormous attention due to their potential applications in wearable and portable devices. To achieve flexibility and stretchability, many efforts have been made with regard to mechanically robust electrodes, interface layers, and photoactive semiconductors. This has greatly improved the performance of the devices. State‐of‐the‐art flexible and stretchable OSCs have achieved a power conversion efficiency of 15.21% (16.55% for tandem flexible devices) and 13%, respectively. Here, the recent progress of flexible and stretchable OSCs in terms of their components and processing methods are summarized and discussed. The future challenges and perspectives for flexible and stretchable OSCs are also presented.
An “S‐shaped, hook‐like” naphthalene diimide derivate, NDI‐BN, is adopted as a cathode interface layer in inverted perovskite solar cells and good power conversion efficiency of 21.32% with enhanced stability is achieved. The relationship between the molecular packing motif of the organic interface layer and the interfacial degradation mechanism is explored.
Ion migration induced interfacial degradation is a detrimental factor for the stability of perovskite solar cells (PSCs) and hence requires special attention to address this issue for the development of efficient PSCs with improved stability. Here, an “S‐shaped, hook‐like” organic small molecule, naphthalene diimide derivative (NDI‐BN), is employed as a cathode interface layer (CIL) to tailor the [6,6]‐phenylC61‐butyric acid methylester (PCBM)/Ag interface in inverted PSCs. By realizing enhanced electron extraction capability via the incorporation of NDI‐BN, a peak power conversion efficiency of 21.32% is achieved. Capacitance–voltage measurements and X‐ray photoelectron spectroscopy analysis confirmed an obvious role of this new organic CIL in successfully blocking ionic diffusion pathways toward the Ag cathode, thereby preventing interfacial degradation and improving device stability. The molecular packing motif of NDI‐BN further unveils its densely packed structure with π–π stacking force which has the ability to effectually hinder ion migration. Furthermore, theoretical calculations reveal that intercalation of decomposed perovskite species into the NDI clusters is considerably more difficult compared with the PCBM counterparts. This substantial contrast between NDI‐BN and PCBM molecules in terms of their structures and packing fashion determines the different tendencies of ion migration and unveils the superior potential of NDI‐BN in curtailing interfacial degradation.
The ternary pseudo‐planar heterojunction strategy is an efficient strategy to optimize the morphology and enlarge the vertical phase separation of active layer, affording the highest power conversion efficiency of 14.25%.
Bulk heterojunction (BHJ) processing technology has had an irreplaceable role in the development of organic solar cells (OSCs) in the past decades due to the significant advantages in achieving high‐power conversion efficiency (PCE). However, the difficulty in exploring and regulating morphology makes it inadequate for upscaling large‐area OSCs. In this work, printable high‐performance ternary devices are fabricated by a pseudo‐planar heterojunction (PPHJ) strategy. The fullerene derivative indene‐C60 bisadduct (ICBA) is incorporated into PM6/IT‐4F system to expand the vertical phase separation and facilitate an obvious PPHJ structure. After the addition of ICBA, the IT‐4F enriches on the surface of active layer, while PM6 is accumulated underneath. Furthermore, it increases the crystallinity of PM6, which facilitates exciton dissociation and charge transfer. Accordingly, 1.05 cm2 devices are fabricated by blade‐coating with an enhanced PCE of 14.25% as compared to the BHJ devices (13.73%). The ternary PPHJ strategy provides an effective way to optimize the vertical phase separation of organic semiconductor during scalable printing methods.
Recent progress of tin and mixed Pb–Sn halide perovskite solar cells is summarized, including an introduction of device structures, fabrication methods, strategies to improve both performance and stability, and an outlook of pure tin‐based halide, mixed Pb–Sn halide, and monolithic all‐perovskite tandem solar cells.
Metal halide perovskites have recently attracted enormous attention for photovoltaic applications due to their superior optical and electrical properties. Lead (Pb) halide perovskites stand out among this material series, with a power conversion efficiency (PCE) over 25%. According to the Shockley–Queisser (SQ) limit, lead halide perovskites typically exhibit bandgaps that are not within the optimal range for single‐junction solar cells. Partial or complete replacement of lead with tin (Sn) is gaining increasing research interest, due to the promise of further narrowing the bandgaps. This enables ideal solar utilization for single‐junction solar cells as well as the construction of all‐perovskite tandem solar cells. In addition, the usage of Sn provides a path to the fabrication of lead‐free or Pb‐reduced perovskite solar cells (PSCs). Recent progress in addressing the challenges of fabricating efficient Sn halide and mixed lead–tin (Pb–Sn) halide PSCs is summarized herein. Mixed Pb–Sn halide perovskites hold promise not only for higher efficiency and more stable single‐junction solar cells but also for efficient all‐perovskite monolithic tandem solar cells.
The technology of pulsed laser irradiation in liquid from a solid target to liquid is pioneered, yielding liquid ternary supranano‐(<10 nm) alloys with a unique core–shell structure. The decoration of such supranano‐alloys as an electron mediator at grain boundaries promotes the electron extraction and transfer of the hybrid perovskite film of a perovskite solar cell and drives the efficiency up to 22.03%.
Creating colloids of liquid metal with tailored dimensions has been of technical significance in nano‐electronics while a challenge remains for generating supranano (<10 nm) liquid metal to unravel the mystery of their unconventional functionalities. Present study pioneers the technology of pulsed laser irradiation in liquid from a solid target to liquid, and yields liquid ternary nano‐alloys that are laborious to obtain via wet‐chemistry synthesis. Herein, the significant role of the supranano liquid metal on mediating the electrons at the grain boundaries of perovskite films, which are of significance to influence the carriers recombination and hysteresis in perovskite solar cells, is revealed. Such embedding of supranano liquid metal in perovskite films leads to a cesium‐based ternary perovskite solar cell with stabilized power output of 21.32% at maximum power point tracing. This study can pave a new way of synthesizing multinary supranano alloys for advanced optoelectronic applications.
Ambipolar black phosphorene (BP) nanosheets with tailored thicknesses concurrently enhance carrier extraction at both the electron‐transport layer/perovskite and hole‐transport layer/perovskite interfaces for high‐efficiency perovskite solar cells, demonstrating the appealing implementation of BP as a dual‐functional carrier‐transport material for a diversity of optoelectronic devices, including solar cells, photodetectors, sensors, light‐emitting diodes, etc.
2D black phosphorene (BP) carries a stellar set of physical properties such as conveniently tunable bandgap and extremely high ambipolar carrier mobility for optoelectronic devices. Herein, the judicious design and positioning of BP with tailored thickness as dual‐functional nanomaterials to concurrently enhance carrier extraction at both electron transport layer/perovskite and perovskite/hole transport layer interfaces for high‐efficiency and stable perovskite solar cells is reported. The synergy of favorable band energy alignment and concerted cascade interfacial carrier extraction, rendered by concurrent positioning of BP, delivered a progressively enhanced power conversion efficiency of 19.83% from 16.95% (BP‐free). Investigation into interfacial engineering further reveals enhanced light absorption and reduced trap density for improved photovoltaic performance with BP incorporation. This work demonstrates the appealing characteristic of rational implementation of BP as dual‐functional transport material for a diversity of optoelectronic devices, including photodetectors, sensors, light‐emitting diodes, etc.
