Solid‐State Dye‐Sensitized Solar Cells Using a Novel Class of Ullazine Dyes as Sensitizers

Here we present the photovoltaic performance of solid‐state dye‐sensitized solar cells (DSCs) using a series of ullazine‐based metal‐free organic sensitizers and spiro‐MeOTAD as a hole‐transport material. A maximum of 4.95% power conversion efficiency measured under standard AM 1.5G illumination (100 mW cm^?2) was achieved with the best performing ullazine dye, and was further improved to 5.40% through co‐sensitization with the triphenylamine‐based organic sensitizer, D35. This study investigates the effect of the molecular structure of the ullazine sensitizer on the performance in solid‐state DSCs.     

New Acetylene‐Bridged 9,10‐Conjugated Anthracene Sensitizers: Application in Outdoor and Indoor Dye‐Sensitized Solar Cells

In this report, a pivotal improvement in the performance of dye‐sensitized solar cells has been achieved, thus taking it one step closer toward the commercialization. Through the stepwise modification on the anthracene‐based organic sensitizers, the alteration of alkyl to alkoxy chain and incorporation of electron deficient moieties in the new sensitizing dyes TY3 , TY4 , and TY6 are found to play a significant role in the efficiency enhancement. The dye TY6 , when tested under 1 sun (AM 1.5G) illumination, is found to exhibit the best efficiency of 8.08% in the series reported here. Taking it further, sensitizer TY6 achieves a milestone by displaying an efficiency of 28.56% when tested under T5 fluorescent illumination of 6000 lux and 20.72% under same illuminance from a commercial light emitting diode light source. Such an excellent performance can be attributed to its outstanding J _SC and V _OC, which are characteristic properties of these anthracene dyes.     

Design of a New Energy‐Harvesting Electrochromic Window Based on an Organic Polymeric Dye,a Cobalt Couple,and PProDOT‐Me2

A new design for an energy‐harvesting electrochromic window (EH‐ECW) based on the fusion of two technologies, organic electrochromic windows and dye‐sensitized solar cells (DSSCs), is presented. Unlike other power‐generating smart windows, such as photoelectrochromic devices that are passive and only contain two states (i.e., a closed‐circuit colored state and an open‐circuit bleaching state), EH‐ECW allows active tuning of the transmittance by varying the applied potential and it functions as a photovoltaic cell based on a DSSC. The resulting device demonstrates a fast switching rate of 1 s in both the bleaching and coloring processes through the use of an electrochromic polymer as a counter electrode layer. To increase the transmittance of the device, a cobalt redox couple and a light‐colored, yet efficient, organic dye are used. The organic dye contains a polymeric structure that contributes to the high cyclic stability. The device exhibits a power conversion efficiency (PCE) of 4.5% (100 mW cm^‐2) under AM 1.5 irradiation, a change in transmittance of 34% upon applied potential, and shows only 3% degradation in the PCE after 5000 cycles.     

Thieno[3,2‐b][1]benzothiophene Derivative as a New π‐Bridge Unit in D–π–A Structural Organic Sensitizers with Over 10.47% Efficiency for Dye‐Sensitized Solar Cells

Three new thieno[3,2‐b][1]benzothiophene ( TBT )‐based donor–π–acceptor (D–π–A) sensitizers, coded as SGT ‐ 121 , SGT ‐ 129 , and SGT ‐ 130 , have been designed and synthesized for dye‐sensitized solar cells (DSSCs), for the first time. The TBT , prepared by fusing thiophene unit with the phenyl unit of triphenylamine donor, is utilized as the π‐bridge for all sensitizers with good planarity. They have been molecularly engineered to regulate the highest occupied molecular orbital (HOMO)‐lowest unoccupied molecular orbital (LUMO) energy levels and extend absorption range as well as to control the electron‐transfer process that can ensure efficient dye regeneration and prevent undesired electron recombination. The photovoltaic performance of SGT‐sensitizer‐based DSSCs employing Co(bpy)₃^2+/3+ (bpy = 2,2′‐bipyridine) redox couple is systematically evaluated in a thorough comparison with Y123 as a reference sensitizer. Among them, SGT ‐ 130 with benzothiadiazole‐phenyl ( BTD ‐ P ) unit as an auxiliary acceptor exhibits the highest power‐conversion efficiency (PCE) of 10.47% with J_sc = 16.77 mA cm^?2, V_oc = 851 mV, and FF = 73.34%, whose PCE is much higher than that of Y123 (9.5%). It is demonstrated that the molecular combination of each fragment in D–π–A organic sensitizers can be a pivotal factor for achieving the higher PCEs and an innovative strategy for strengthening the drawbacks of the π‐bridge.     

Improved Performance and Reliability of p‐i‐n Perovskite Solar Cells via Doped Metal Oxides

Perovskite photovoltaics (PVs) have attracted attention because of their excellent power conversion efficiency (PCE). Critical issues related to large‐area PV performance, reliability, and lifetime need to be addressed. Here, it is shown that doped metal oxides can provide ideal electron selectivity, improved reliability, and stability for perovskite PVs. This study reports p‐i‐n perovskite PVs with device areas ranging from 0.09 cm² to 0.5 cm² incorporating a thick aluminum‐doped zinc oxide (AZO) electron selective contact with hysteresis‐free PCE of over 13% and high fill factor values in the range of 80%. AZO provides suitable energy levels for carrier selectivity, neutralizes the presence of pinholes, and provides intimate interfaces. Devices using AZO exhibit an average PCE increase of over 20% compared with the devices without AZO and maintain the high PCE for the larger area devices reported. Furthermore, the device stability of p‐i‐n perovskite solar cells under the ISOS‐D‐1 is enhanced when AZO is used, and maintains 100% of the initial PCE for over 1000 h of exposure when AZO/Au is used as the top electrode. The results indicate the importance of doped metal oxides as carrier selective contacts to achieve reliable and high‐performance long‐lived large‐area perovskite solar cells.     

Study of Burn‐In Loss in Green Solvent‐Processed Ternary Blended Organic Photovoltaics Derived from UV‐Crosslinkable Semiconducting Polymers and Nonfullerene Acceptors

This work deals with the investigation of burn‐in loss in ternary blended organic photovoltaics (OPVs) prepared from a UV‐crosslinkable semiconducting polymer (P2FBTT‐Br) and a nonfullerene acceptor (IEICO‐4F) via a green solvent process. The synthesized P2FBTT‐Br can be crosslinked by UV irradiation for 150 s and dissolved in 2‐methylanisole due to its asymmetric structure. In OPV performance and burn‐in loss tests performed at 75 °C or AM 1.5G Sun illumination for 90 h, UV‐crosslinked devices with PC₇₁BM show 9.2% power conversion efficiency (PCE) and better stability against burn‐in loss than pristine devices. The frozen morphology resulting from the crosslinking prevents lateral crystallization and aggregation related to morphological degradation. When IEICO‐4F is introduced in place of a fullerene‐based acceptor, the burn‐in loss due to thermal aging and light soaking is dramatically suppressed because of the frozen morphology and high miscibility of the nonfullerene acceptor (18.7% → 90.8% after 90 h at 75 °C and 37.9% → 77.5% after 90 h at AM 1.5G). The resulting crosslinked device shows 9.4% PCE (9.8% in chlorobenzene), which is the highest value reported to date for crosslinked active materials, in the first green processing approach.     

Spiro‐Phenylpyrazole‐9,9′‐Thioxanthene Analogues as Hole‐Transporting Materials for Efficient Planar Perovskite Solar Cells

Perovskite solar cells have emerged as a promising technique for low‐cost, light weight, and highly efficient photovoltaics. However, they still largely rely on 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) to serve as hole‐transporting materials (HTMs). Here, a series of HTMs with small molecular weight is designed, which are constructed on a spiro core involving phenylpyrazole and a second heteroaromatics, i.e., xanthene (O atom), thioxanthene (S atom), and acridine (N atom). Through varying from phenylpyrazole substituted xanthene ( PPyra‐XA ), thioxanthene ( PPyra‐TXA ), to acridine ( PPyra‐ACD ), their optical and electrochemical properties, hole mobilities, and the photovoltaic performance are optimized. As a consequence, PPyra‐TXA based device exhibits the highest power conversion efficiency (PCE) of 18.06%, outperforming that of Spiro‐OMeTAD (16.15%), which could be attributed to the enhancement of hole mobility exerted by the thioxanthene. In addition, the dopant‐free device shows PCE of 11.7%. These results open a new direction for designing spiro‐HTMs by simple modification of chemical structures.     

MoS2‐Based All‐Purpose Fibrous Electrode and Self‐Powering Energy Fiber for Efficient Energy Harvesting and Storage

Here an all‐purpose fibrous electrode based on MoS₂ is demonstrated, which can be employed for versatile energy harvesting and storage applications. In this coaxial electrode, ultrathin MoS₂ nanofilms are grown on TiO₂ nanoparticles coated carbon fiber. The high electrochemical activity of MoS₂ and good conductivity of carbon fiber synergistically lead to the remarkable performances of this novel composite electrode in fibrous dye‐sensitized solar cells (showing a record‐breaking conversion efficiency of 9.5%) and high‐capacity fibrous supercapacitors. Furthermore, a self‐powering energy fiber is fabricated by combining a fibrous dye‐sensitized solar cell and a fibrous supercapacitor into a single device, showing very fast charging capability (charging in 7 s under AM1.5G solar illumination) and an overall photochemical‐electricity energy conversion efficiency as high as 1.8%. In addition, this wire‐shaped electrode can also be used for fibrous Li‐ion batteries and electrocatalytic hydrogen evolution reactions. These applications indicate that the MoS₂‐based all‐purpose fibrous electrode has great potential for the construction of high‐performance flexible and wearable energy devices.     

4‐Tert‐butylpyridine Free Organic Hole Transporting Materials for Stable and Efficient Planar Perovskite Solar Cells

4‐Tert ‐butylpyridine (t BP) is an important additive in triarylamine‐based organic hole‐transporting materials (HTMs) for improving the efficiency and steady‐state performance of perovskite solar cells (PVSCs). However, the low boiling point of t BP (196 °C) significantly affects the long‐term stability and device performance of PVSCs. Herein, the design and synthesis of a series of covalently linked Spiro[fluorene‐9,9′‐xanthene] (SFX)‐based organic HTMs and pyridine derivatives to realize efficient and stable planar PVSCs are reported. One of the tailored HTMs, N2,N2,N7,N7‐tetrakis(4‐methoxyphenyl)‐3′,6′‐bis(pyridin‐4‐ylmethoxy) spiro[fluorene‐9,9′‐xanthene]‐2,7‐diamine ( XPP ) with two para‐position substituted pyridines that immobilized on the SFX core unit shows a high power conversion efficiency (PCE) of 17.2% in planar CH₃NH₃PbI₃‐based PVSCs under 100 mW cm^?2 AM 1.5G solar illumination, which is much higher than the efficiency of 5.5% that using the well‐known 2,2′,7,7′‐tetrakis‐(N ,N ‐di‐p ‐methoxy‐phenyl‐amine)9,9′‐spirobifluorene (Spiro‐OMeTAD) as HTM (without t BP) under the same condition. Most importantly, the pyridine‐functionalized HTM‐based PVSCs without t BP as additive show much better long‐term stability than that of the state‐of‐the‐art HTM Spiro‐OMeTAD‐based solar cells that containing t BP as additive. This is the first case that the t BP‐free HTMs are demonstrated in PVSCs with high PCEs and good stability. It paves the way to develop highly efficient and stable t BP‐free HTMs for PVSCs toward commercial applications.     

Water‐soluble 3,4:9,10‐perylene tetracarboxylic ammonium as a high‐performance fluorochrome for living cells staining

Highly water‐soluble 3,4:9,10‐perylene tetracarboxylic ammonium with quantitative fluorescence quantum yield was designed. Owing to the high negative electrostatic potential of the perylene plane, the perylene dye remained stable over a broad pH range and was successfully applied as a high‐performance fluorochrome for living hippocampal neurons staining. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecularly Engineered Phthalocyanines as Hole‐Transporting Materials in Perovskite Solar Cells Reaching Power Conversion Efficiency of 17.5%

Easily accessible tetra‐5‐hexylthiophene‐, tetra‐5‐hexyl‐2,2′‐bisthiophene‐substituted zinc phthalocyanines (ZnPcs) and tetra‐tert ‐butyl ZnPc are employed as hole‐transporting materials in mixed‐ion perovskite [HC(NH₂)₂]_0.85(CH₃NH₃)_0.15Pb(I_0.85Br_0.15)₃ solar cells, reaching the highest power conversion efficiency (PCE) so far for phthalocyanines. Results confirm that the photovoltaic performance is strongly influenced by both, the individual optoelectronic properties of ZnPcs and the aggregation of these tetrapyrrolic semiconductors in the solid thin film. The optimized devices exhibit PCE of 15.5% when using tetra‐5‐hexyl‐2,2′‐bisthiophene substituted ZnPcs, 13.3% for tetra‐tert ‐butyl ZnPc, and a record 17.5% for tetra‐5‐hexylthiophene‐based analogue under standard global 100 mW cm^?2 AM 1.5G illumination. These results boost up the potential of solution‐processed ZnPc derivatives as stable and economic hole‐transport materials for large‐scale applications, opening new frontiers toward a realistic, efficient, and inexpensive energy production.     

Green‐Solvent‐Processed All‐Polymer Solar Cells Containing a Perylene Diimide‐Based Acceptor with an Efficiency over 6.5%

To realize high power conversion efficiencies (PCEs) in green‐solvent‐processed all‐polymer solar cells (All‐PSCs), a long alkyl chain modified perylene diimide (PDI)‐based polymer acceptor PPDIODT with superior solubility in nonhalogenated solvents is synthesized. A properly matched PBDT‐TS1 is selected as the polymer donor due to the red‐shifted light absorption and low‐lying energy level in order to achieve the complementary absorption spectrum and matched energy level between polymer donor and polymer acceptor. By utilizing anisole as the processing solvent, an optimal efficiency of 5.43% is realized in PBDT‐TS1/PPDIODT‐based All‐PSC with conventional configuration, which is comparable with that of All‐PSCs processed by the widely used binary solvent. Due to the utilization of an inverted device configuration, the PCE is further increased to over 6.5% efficiency. Notably, the best‐performing PCE of 6.58% is the highest value for All‐PSCs employing PDI‐based polymer acceptors and green‐solvent‐processed All‐PSCs. The excellent photovoltaic performance is mainly attributed to a favorable vertical phase distribution, a higher exciton dissociation efficiency (P_diss) in the blend film, and a higher electrode carrier collection efficiency. Overall, the combination of rational molecular designing, material selection, and device engineering will motivate the efficiency breakthrough in green‐solvent‐processed All‐PSCs.     

Two Channels of Charge Generation in Perylene Monoimide Solid‐State Dye‐Sensitized Solar Cells

The mechanism of charge generation in solid‐state dye‐sensitized solar cells using triarylamine‐substituted perylene monoimide dyes is studied by vis‐NIR broadband pump‐probe transient absorption spectroscopy. The experiments demonstrate that photoinduced electron injection into the TiO₂ can only occur in regions where Li⁺, from the commonly used Li‐TFSI additive salt, is present on the TiO₂ surface. Incomplete surface coverage by Li⁺ means that some dye excitons cannot inject their electron into the TiO₂. However it is observed in the solar cell structure that some of the dye excitons that cannot directly inject an electron still contribute to free charge generation by the previously hypothesized reductive quenching mechanism (hole transfer to the solid‐state hole transporter followed by electron injection from the dye anion into the TiO₂). The contribution of reductive quenching to the quantum efficiency of charge generation is significant, raising it from 68% to over 80%. Optimization of this reductive quenching pathway could be exploited to maintain high quantum efficiency in dyes with greater NIR absorption to achieve overall enhancements in device performance. It is demonstrated that broadband NIR transient spectroscopy is necessary to obtain population kinetics in these systems, as strong Stark effects distort the population kinetics in the visible region.     

Tantalum Nitride Electron‐Selective Contact for Crystalline Silicon Solar Cells

Minimizing carrier recombination at contact regions by using carrier‐selective contact materials, instead of heavily doping the silicon, has attracted considerable attention for high‐efficiency, low‐cost crystalline silicon (c‐Si) solar cells. A novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN _x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties to the silicon surface, due to their small conduction band offset and large valence band offset. Thin TaN_x interlayers provide moderate passivation of the silicon surfaces while simultaneously allowing a low contact resistivity to n‐type silicon. A power conversion efficiency (PCE) of over 20% is demonstrated with c‐Si solar cells featuring a simple full‐area electron‐selective TaN_x contact, which significantly improves the fill factor and the open circuit voltage (V_oc) and hence provides the higher PCE. The work opens up the possibility of using metal nitrides, instead of metal oxides, as carrier‐selective contacts or electron transport layers for photovoltaic devices.     

Hexylthiophene‐Featured D–A–π–A Structural Indoline Chromophores for Coadsorbent‐Free and Panchromatic Dye‐Sensitized Solar Cells

For a sensitizer with a strong π‐conjugation system, a coadsorbent is needed to hinder dye aggregation. However, coadsorption always brings a decrease in dye coverage on the TiO₂ surface. Organic ‘‘D–A–π–A’’ dyes, WS‐6 and WS‐11, are designed and synthesized based on the known WS‐2 material for coadsorbent‐free, dye‐sensitized solar cells (DSSCs). Compared with the traditional D–π–A structure, these D–A–π–A indoline dyes, with the additional incorporated acceptor unit of benzothiadiazole in the π‐conjugation, exhibit a broad photoresponse, high redox stability, and convenient energy‐level tuning. The attached n‐hexyl chains in both dyes are effective to suppress charge recombination, resulting in a decreased dark current and enhanced open‐circuit voltage. Electrochemical impedance spectroscopy studies indicate that both the resistance for charge recombination and the electron lifetime are increased after the introduction of alkyl chains to the dye molecules. Without deoxycholic acid coadsorption, the power‐conversion efficiency of WS‐6 (7.76%) on a 16 μm‐thick TiO₂ film device is 45% higher than that of WS‐2 (5.31%) under the same conditions. The additional n‐hexylthiophene in WS‐11 extends the photoresponse to a panchromatic spectrum but causes a low incident photon‐to‐current conversion efficiency.     

Molecular Engineering Using an Anthanthrone Dye for Low‐Cost Hole Transport Materials: A Strategy for Dopant‐Free,High‐Efficiency,and Stable Perovskite Solar Cells

In this report, highly efficient and humidity‐resistant perovskite solar cells (PSCs) using two new small molecule hole transporting materials (HTM) made from a cost‐effective precursor anthanthrone (ANT) dye, namely, 4,10‐bis(1,2‐dihydroacenaphthylen‐5‐yl)‐6,12‐bis(octyloxy)‐6,12‐dihydronaphtho[7,8,1,2,3‐nopqr]tetraphene (ACE‐ANT‐ACE) and 4,4′‐(6,12‐bis(octyloxy)‐6,12‐dihydronaphtho[7,8,1,2,3‐nopqr]tetraphene‐4,10‐diyl)bis(N,N‐bis(4‐methoxyphenyl)aniline) (TPA‐ANT‐TPA) are presented. The newly developed HTMs are systematically compared with the conventional 2,2′,7,7′‐tetrakis(N,N′‐di‐p‐methoxyphenylamino)‐9,9′‐spirbiuorene (Spiro‐OMeTAD). ACE‐ANT‐ACE and TPA‐ANT‐TPA are used as a dopant‐free HTM in mesoscopic TiO₂/CH₃NH₃PbI₃/HTM solid‐state PSCs, and the performance as well as stability are compared with Spiro‐OMeTAD‐based PSCs. After extensive optimization of the metal oxide scaffold and device processing conditions, dopant‐free novel TPA‐ANT‐TPA HTM‐based PSC devices achieve a maximum power conversion efficiency (PCE) of 17.5% with negligible hysteresis. An impressive current of 21 mA cm^?2 is also confirmed from photocurrent density with a higher fill factor of 0.79. The obtained PCE of 17.5% utilizing TPA‐ANT‐TPA is higher performance than the devices prepared using doped Spiro‐OMeTAD (16.8%) as hole transport layer at 1 sun condition. It is found that doping of LiTFSI salt increases hygroscopic characteristics in Spiro‐OMeTAD; this leads to the fast degradation of solar cells. While, solar cells prepared using undoped TPA‐ANT‐TPA show dewetting and improved stability. Additionally, the new HTMs form a fully homogeneous and completely covering thin film on the surface of the active light absorbing perovskite layers that acts as a protective coating for underlying perovskite films. This breakthrough paves the way for development of new inexpensive, more stable, and highly efficient ANT core based lower cost HTMs for cost‐effective, conventional, and printable PSCs.     

Amino‐Functionalized Conjugated Polymer as an Efficient Electron Transport Layer for High‐Performance Planar‐Heterojunction Perovskite Solar Cells

An amino‐functionalized copolymer with a conjugated backbone composed of fluorene, naphthalene diimide, and thiophene spacers (PFN‐2TNDI) is introduced as an alternative electron transport layer (ETL) to replace the commonly used [6,6]‐Phenyl‐C61‐butyric acid methyl ester (PCBM) in the p–i–n planar‐heterojunction organometal trihalide perovskite solar cells. A combination of characterizations including photoluminescence (PL), time‐resolved PL decay, Kelvin probe measurement, and impedance spectroscopy is used to study the interfacial effects induced by the new ETL. It is found that the amines on the polymer side chains not only can passivate the surface traps of perovskite to improve the electron extraction properties, they also can reduce the work function of the metal cathode by forming desired interfacial dipoles. With these dual functionalities, the resulted solar cells outperform those based on PCBM with power conversion efficiency (PCE) increased from 12.9% to 16.7% based on PFN‐2TNDI. In addition to the performance enhancement, it is also found that a wide range of thicknesses of the new ETL can be applied to produce high PCE devices owing to the good electron transport property of the polymer, which offers a better processing window for potential fabrication of perovskite solar cells using large‐area coating method.     

Overcoming the “Light‐Soaking” Issue in Inverted Organic Solar Cells by the Use of Al:ZnO Electron Extraction Layers

A common phenomenon of organic solar cells (OSCs) incorporating metal‐oxide electron extraction layers is the requirement to expose the devices to UV light in order to improve device characteristics – known as the so‐called “light‐soaking” issue. This behaviour appears to be of general validity for various metal‐oxide layers, various organic donor/acceptor systems, and regardless if single junction devices or multi stacked cells are considered. The requirement of UV exposure of OSCs may impose severe problems if substrates with limited UV transmission, UV blocking filters or UV to VIS down‐conversion concepts are applied. In this paper, we will demonstrate that this issue can be overcome by the use of Al doped ZnO (AZO) as electron extraction interlayer. In contrast to devices based on TiO_x and ZnO, the AZO devices show well‐behaved solar cell characteristics with a high fill factor (FF) and power conversion efficiency (PCE) even without the UV spectral components of the AM1.5 solar spectrum. As opposed to previous claims, our results indicate that the origin of s‐shaped characteristics of the OSCs is the metal‐oxide/organic interface. The electronic structures of the TiO_x/fullerene and AZO/fullerene interfaces are studied by photoelectron spectroscopy, revealing an electron extraction barrier for the TiO_x/fullerene case and facilitated electron extraction for AZO/fullerene. These results are of general relevance for organic solar cells based on various donor acceptor active systems.     

Mesoporous TiO2 Beads Offer Improved Mass Transport for Cobalt‐Based Redox Couples Leading to High Efficiency Dye‐Sensitized Solar Cells

Overcoming ionic diffusion limitations is essential for the development of high‐efficiency dye‐sensitized solar cells based on cobalt redox mediators. Here, improved mass transport is reported for photoanodes composed of mesoporous TiO₂ beads of varying pore sizes and porosities in combination with the high extinction YD2‐o‐C8 porphyrin dye. Compared to a photoanode made of 20 nm‐sized TiO₂ particles, electrolyte diffusion through these films is greatly improved due to the large interstitial pores between the TiO₂ beads, resulting in up to 70% increase in diffusion‐limited current. Simultaneously, transient photocurrent measurements reveal no mass transport limitations for films of up to 10 μm thickness. In contrast, standard photoanodes made of 20 nm‐sized TiO₂ particles show non‐linear behavior in photocurrent under 1 sun illumination for a film thickness as low as 7 μm. By including a transparent thin mesoporous TiO₂ underlayer in order to reduce optical losses at the fluorine‐doped tin oxide (FTO)‐TiO₂ interface, an efficiency of 11.4% under AM1.5G 1 sun illumination is achieved. The combination of high surface area, strong scattering behavior, and high porosity makes these mesoporous TiO₂ beads particularly suitable for dye‐sensitized solar cells using bulky redox couples and/or viscous electrolytes.     

MXene‐Contacted Silicon Solar Cells with 11.5% Efficiency

MXene, a new class of 2D materials, has gained significant attention owing to its attractive electrical conductivity, tunable work function, and metallic nature for wide range of applications. Herein, delaminated few layered Ti₃C₂T_x MXene contacted Si solar cells with a maximum power conversion efficiency (PCE) of ≈11.5% under AM1.5G illumination are demonstrated. The formation of an Ohmic junction of the metallic MXene to n⁺‐Si surface efficiently extracts the photogenerated electrons from n⁺np⁺‐Si, decreases the contact resistance, and suppresses the charge carrier recombination, giving rise to excellent open‐circuit voltage and short‐circuit current density. The rapid thermal annealing process further improves the electrical contact between Ti₃C₂T_x MXene and n⁺‐Si surface by reducing sheet resistance, increasing electrical conductivity, and decreasing cell series resistance, thus leading to a remarkable improvement in fill factor and overall PCE. The work demonstrated here can be extended to other MXene compositions as potential electrodes for developing highly performing solar cells.