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An exquisite, engineering of two poor hole transporting materials (HTMs, SnO, and PDTON) to form an excellent double‐layered HTL (SnO/PDTON) for inverted tin‐perovskite solar modules (TPSMs) is developed. SnO/PDTON has better photovoltaic performance than the commonly used PEDOT:PSS HTM when large‐area TPSMs are fabricated. Thermally evaporated SnO (that is a simple, available oxide with high hole mobility, good transparency, and adjustable frontier orbitals energy levels) film is used as a main hole transporting layer (HTL). Amphiphilic polymer PDTON (having the amine and ether groups on the side chains) film is used as a Co‐HTL, cross‐linker, passivator, and interface modification agent, as unveiled various physicochemical studies. Double‐layered SnO/PDTON with a flat morphology and good affinity toward perovskite precursor solution creates also a proper surface for depositing large‐area, high‐quality TPsk film. Therefore, TPSM (25.2 cm2 active area on 10 cm × 10 cm ITO substrate) based on double‐layered SnO/PDTON HTL achieving an efficiency over 10% with a negligible current hysteresis is reported for the first time. This study emphasizes not only the exquisite design of combining the specific characteristics of two prosaic HTMs to become a good double‐layered HTL but also gives a direction toward fabricating TPSMs to be applied in all‐perovskite tandem solar module. [ABSTRACT FROM AUTHOR]

Low‐temperature sol‐gel prepared ZnCo2O4 spinel‐based thin films are developed as high‐performance hole transporting layer (HTL) for coating perovskite film (NA‐Psk) from the basic MAPbI3/ACN/CH3NH2 solution in air without using anti‐solvent. Inverted PSC based on 2 mole% (vs Zn) Cu2+ doped ZnCo2O4 (2%Cu@ZnCo2O4) HTL and NA‐Psk absorber exhibit the maximum power conversion efficiency (PCE) of 20.0% with no current hysteresis while the cell based on ZnCo2O4 and PEDOT:PSS HTL (using NA‐Psk absorber) achieves the PCE of 15.79% and 12.3% with a current hysteresis index of 9.8% and 32.4%, respectively. Without encapsulation, PSCs based on 2%Cu@ZnCo2O4, ZnCo2O4, and PEDOT:PSS HTLs maintain 90%, 77%, and 12%, respectively of the original efficiency by standing in ambient atmosphere (temperature: 20–25 °C, RH:30%–40%) for 1800 h. Large area (10 cm × 10 cm substrate) perovskite mini‐module (PSM) with PCE over 15% is also demonstrated by using sol‐gel prepared 2%Cu@ZnCo2O4 HTL. The poor photovoltaic performance of PEDOT:PSS HTL is due to the basic MAPbI3/ACN/CH3NH2 solution will deprotonate the acidic PEDOT:PSS to reduce its conductivity whereas ZnCo2O4 HTL are not affected by basic perovskite precursor solution. [ABSTRACT FROM AUTHOR]

High-quality perovskite film is deposited on a 30 cm × 40 cm LiCoO2-coated ITO/glass via newly developed freely falling anti-solvent extraction (FFASE) method followed by post watervapor annealing in an ambient atmosphere. Perovskite solar modules (PSMs, active area of 25.2 cm2 with mask) based on this high-quality film achieve the highest efficiency of 16.04 and 30.76% under 1 sun (100 mW cm-2) and 945 lux fluorescent light illumination, respectively. The encapsulated PSMs are stable at -20 to 80 °C thermal cycling and keep high efficiency at temperature as low as -20 °C and as high as 80 °C. When the encapsulated PSM is heated at 85 °C and 85% relative humidity under room lighting or heated at 60 °C under AM1.5 (100 mW cm-2) illumination for 1000 h, loses only "8% of its original efficiency. The high stability of PSMs is due to very high quality perovskite absorber being used. The underlying concept of the FFASE method for extracting the solvent from the large-area perovskite precursor film is that the whole precursor film contacts with the fresh anti-solvent during the crystallization stage. [ABSTRACT FROM AUTHOR]

The defects at the interface and grain boundaries of perovskite films downgrade the performance of perovskite solar cells (PSCs) dramatically. Hence, improving perovskite film quality is essential for the achievement of high-performance solar cells. Herein, three new dicyclopentadithienothiophene (DCDTT)-based non-fullerene acceptors (NFAs) IN-DCDTT (1), INCl-DCDTT (2), and INBr-DCDTT (3) are developed as a promising platform for organic–inorganic hybrid perovskite solar cells to achieve simple preparation, high efficiency, and good stability. SEM and XRD data indicate that, with the addition of chlorinated NFA 2 in the active layer preparation, perovskite hybrid films exhibit larger grain sizes and higher crystallinity than pristine perovskite films. As shown by EDS and IR, all the non-fullerene acceptors (compounds 1–3) with functional carbonyl (C＝O) and cyano (C≡N) groups have good interaction with undercoordinated Pb atoms and passivate the trap states in the perovskite films. Time-resolved photoluminescence reveals that the molecule INCl-DCDTT (2) facilitates efficient hole extraction. Consequently, solar cells based on 2−perovskite hybrid films yield an excellent power conversion efficiency of 21.39% with an FF of 0.82, a Jsc of 23.71 mA cm−2, and a Voc of 1.10 V, which represents a significant improvement as compared to a PCE of 17% obtained for the control device. Meanwhile, devices based on IN-DCDTT (1) and INBr-DCDTT (3)−perovskite hybrid films also show enhanced performance with a slightly lower PCE of 19.21% and 20.59%, respectively than cells based on 2−perovskite hybrid films. The cost-effective chlorinated INCl-DCDTT (2) and brominated INBr-DCDTT (3) organic small molecules were successfully used as donor passivation agents to improve the photovoltaic performance of Pb-based PSCs. Furthermore, compound 1–3 derived PSC devices also exhibit excellent long-term stability enhancement. In particular, a device based on INCl-DCDTT (2) treated perovskite retains ∼90% of the initial PCE after 63 days in a glove box as compared to that (55%) of the control device. This simple surface treatment, by the addition of new NFAs, provides a new strategy to simultaneously passivate surface defects and enhance charge transport at the device interface. [ABSTRACT FROM AUTHOR]

The oxide/nitride passivation and the flip‐chip package technology are developed for the perovskite solar cells. The heat resulting from the physical vapor deposition decomposes the active perovskite layer and degrades the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si‐nitride passivation processed by plasma‐enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1%. It is because that the plasma‐enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency‐decay curves of the flip‐chip packaged perovskite solar cells, the characteristic time of the reliability‐tested solar cell can be calculated to be 145.8, 390.7, and 4864 h for air‐ambient, glove chamber, and water‐ambient tests, respectively. It is concluded that the concentration of O2(g) in the reliability test ambient is the root cause for the efficiency degradation of the perovskite solar cells. The low mobility of O2(g) under the water‐ambient reliability test results in the low probability of the adsorption of O2(g) on the surface of the flip‐chip package, which is the key factor for the least efficiency degradation of the perovskite solar cells among the three reliability tests. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have received great attention due to their outstanding performance and their low processing costs. To boost their performance, one approach is to reinforce the built‐in electric field (BEF) to promote oriented carrier transport. The BEF is maximized by reinforcing the work function difference between cathode and anode (Δμ1) and increasing the work function difference between lower and upper surfaces of perovskite film (Δμ2) via introduction of electric dipole molecules, denoted as PTFCN and CF3BACl. The synergistic reinforcement of BEF improves charge transport and collection, and realizes markedly high photovoltaic performances with the best power conversion efficiency (PCE) up to 21.5%, a growth of 15.6% as compared to the control device, which is higher than the superposition of improvements achieved by either raising Δμ1 or Δμ2. Importantly, dual‐functional CF3BACl not only supplies dipole effect for tuning the surface potential of perovskite but offers hydrophobic trifluoride group toward the long‐term stable unencapsulated PSCs retaining more than 95% PCE after storing 2000 h under ambient conditions. This work demonstrates the synergistic effect of Δμ1 and Δμ2, providing an effective strategy for the further development of PSC in terms of photovoltaic conversion and stability. [ABSTRACT FROM AUTHOR]

A new inorganic hole transporting layer, a sputtering made LiCoO2 film, was developed and used in an inverted perovskite solar cell (PSC) and sub-module (PSM). The LiCoO2 film prepared by RF magnetron sputtering is composed of nano-sized particles and a superhydrophilic surface after treating it with UV–ozone, and therefore can be wetted evenly with a (MAI + PbI2)/(DMF + DMSO) precursor solution. By applying chlorobenzene as an anti-solvent, a very dense film with big perovskite grains was formed. After depositing the C60 electron transporting layer, BCP hole blocking layer and Ag electrode, the best perovskite solar cell achieves a power conversion efficiency (PCE) of 19% with negligible current hysteresis. The high-efficiency cell is stable up to 90 °C in the inert atmosphere without encapsulation, and the PCE only decreases by 2% when the cell was heated at 100 °C for 30 minutes. When the cell was heated at 100 °C for 5 days, the PCE decreases by only 40%; nevertheless, under the same heating conditions, the efficiency of the PSC based on the PEDOT:PSS HTL is lost totally. The superhydrophilic surface of LiCoO2 made the even wetting of the large surface area with the perovskite precursor solution possible. Therefore the perovskite solar sub-module with an active area of 25.2 cm2 (on a 10 cm × 10 cm substrate) can be fabricated to achieve a power conversion efficiency of 16% which was further verified to be 15%. The high-efficiency sub-module based on the LiCoO2 HTL also shows good thermal stability, and ca. 10% of the efficiency was lost by heating at 100 °C for 30 minutes. The development of new inorganic hole transporting layers for large area, thermally stable and highly efficient perovskite solar sub-modules closes the gap for their near-future market exploitation. [ABSTRACT FROM AUTHOR]

Anatase titanium dioxide (an-TiO2) is often used as the electron transporting material (ETM) in planar-heterojunction perovskite solar cells (PSCs) because of its excellent semiconductor characteristics, outstanding optical transmittance, and suitable band structure. Herein, we report an inexpensive method for mass-scale production of TiO2 ETMs at room temperature (RT ∼ 30 °C), involving the grinding of large clumps of an-TiO2 to form a suspension of TiO2 nanoparticles (NPs) in isopropyl alcohol for meso-superstructured PSCs. This process does not involve any chemical synthesis; it is a purely physical process. The lowest unoccupied molecular orbital (LUMO) of ground an-TiO2 NPs, estimated using ultraviolet photoelectron spectroscopy (UPS), was ca. 4.06 eV, which is a salient feature for the active layer. A regular perovskite solar cell (PSC) based on a CH3NH3PbI3 absorber and ground an-TiO2 ETL exhibited a champion power conversion efficiency (PCE) of 17.43% with an active area of 0.1 cm2. The same ground an-TiO2 NPs were used to fabricate a large-area (designated area: 25.2 cm2) PSC and a PCE of 14.19% was achieved. PSC devices incorporating the ground an-TiO2 NP ETLs exhibited an attractive long-term device stability, with the PCE retaining approximately 85% of the initial values after 80 days. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H2O<0.1 ppm, O2<10 ppm). The PCE of the solar cell based on a perovskite film having the grain size larger than 1 μm ( D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H2O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. [ABSTRACT FROM AUTHOR]

An organic lead halide perovskite film proved to be an excellent light harvesting material for solar cells. The ability to prepare high quality perovskite films, with large areas, for solar modules using simple methods is essential for commercializing this promising photovoltaic technology. By combining the composition of the halogens (Cl can improve the morphology of the film by reducing the crystallization rate, and Br can increase the Voc and stabilize the crystal lattice) and film casting engineering (hot solution spin-coating (HSS) and solvent annealing (SA)), high quality single-phase mixed-halide perovskite films can be prepared using a one-step method. This new method can not only prepare high quality, small area films reproducibly but also be adopted readily to prepare high quality homogeneous films with large areas for perovskite solar modules. An inverted mixed-halide perovskite solar module (active area of 25.2 cm2) achieves the highest efficiency of 14.3% with a remarkably high FF of 74.4% and has no current hysteresis. [ABSTRACT FROM AUTHOR]

A two-step, spin-coating process to synthesize a high quality perovskite film at room temperature at ambient atmosphere is reported. Combining an optimized PEDOT:PSS hole-transport layer and a PC71BM acceptor, the device achieved a power conversion efficiency of 16.31% with a remarkably high Voc of 1.05 V and FF of 0.78. The efficiency reproducibility of the devices is also high: 80% of devices achieve efficiency higher than 15%. [ABSTRACT FROM AUTHOR]

The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations. [ABSTRACT FROM AUTHOR]

Solid-state sensors are stable and inexpensive electric transducers for biomedical measurement. This study proposes a microfluidic chip incorporated with a solid-state sensor for measuring glucose and creatinine in blood serum. Magnetic beads are employed to immobilize enzymes and deliver them in a micro-channel. Glucose and creatinine can be measured at 2-8 mM and 10-2 to 10 mM, respectively, which is a meaningful range in human blood. The immobilization approach also addresses the issue of the long-term preservation of enzymes in microfluidic devices. The proposed device is suitable for multi-target measurement in a point-of-care system. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality perovskite film is prepared in air reproducibly. The nonvolatile nature of 2P and the formation of MAI–PbI2–2P adduct widen the time window for antisolvent engineering, and SASE enhances the solvent exchange rate of the precursor film to form a high‐quality perovskite film in air. An inverted cell (based on the postsolvent‐treated perovskite absorber) exhibits a power conversion efficiency of more than 18%. This film preparation method is feasible for depositing a high‐quality mixed‐cation or mixed‐cation, mixed‐halide perovskite film on both PEDOT:PSS and TiO2 surfaces to fabricate inverted and regular PSCs, respectively, to achieve efficiencies of more than 16%. More importantly, high‐quality, large‐area MAPbI3 film is prepared reproducibly in air for fabricating perovskite submodules to achieve an efficiency of 14% (verified at 13.04% after the cell is packed for efficiency evaluation). [ABSTRACT FROM AUTHOR]

Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. [ABSTRACT FROM AUTHOR]

The refractive index and extinction coefficient of a triiodide perovskite absorber (TPA) were obtained by fitting the transmittance spectra of TPA/PEDOT:PSS/ITO/glass using the transfer matrix method. Cu nanoplasmonic structures were designed to enhance the exciton generation in the TPA and to simultaneously reduce the film thickness of the TPA. Excitons were effectively generated at the interface between TPA and Cu nanoparticles, as observed through the 3D finite-difference time-domain method. The exciton distribution is advantageous for the exciton dissociation and carrier transport. [ABSTRACT FROM AUTHOR]

A simple, synergistic engineering of the conduction band (CB), conductivity, and interface of TiO 2 -based bilayered electron transport layers (ETLs) via scalable TiO 2 and SnO 2 nanoparticles processed at low temperature (≤ 100 °C) for regular planar perovskite solar cells (PSCs) was developed. The bottom layer (Lt-TiO 2 :SnO 2 nanocomposite film) was prepared by spin coating from the ethanol suspension of small ground TiO 2 nanoparticles with big ground SnO 2 nanoparticles as the additive. The top C-SnO 2 layer (spin-coated from the concentrated commercial SnO 2 nanoparticles (C-SnO 2 NPs, 20 wt %, 7 nm in size suspended in H 2 O)) can be regarded as an interlayer between Lt-TiO 2 :SnO 2 and perovskite (Psk) absorbers. Bilayered Lt-TiO 2 :SnO 2 /C-SnO 2 ETLs are dense films with a cascade CB, good conductivity, facile electron extraction/transport ability, and a highly hydrophilic surface for depositing high-quality Psk films. Regular planar PSCs based on Lt-TiO 2 :SnO 2 /C-SnO 2 ETLs combined with a (FAI) 0.90 (PbI 2 ) 0.94 (MABr) 0.10 (PbBr 2 ) 0.10 absorber and a spiro-OMeTAD hole transporter achieved the highest power conversion efficiency of 22.04% with a negligible current hysteresis. The champion cell lost less than 3% of the initial efficiency under continuous room lighting (1000 lux) for 1000 h (lost 10% after 2184 h) without encapsulation under an inert atmosphere. Four related low-temperature-processed ETLs (Lt-TiO 2 /C-SnO 2 , Lt-C-SnO 2 , Lt-TiO 2 :SnO 2 , and Lt-TiO 2 ) were fabricated using the same metal oxide nanoparticle suspensions and studied simultaneously to reveal the function of each metal oxide in the bilayered Lt-TiO 2 :SnO 2 /C-SnO 2 ETLs. In the bottom Lt-TiO 2 :SnO 2 layer, small TiO 2 nanoparticles were needed for making a dense film, and highly conducting big SnO 2 nanoparticles are used to increase the conductivity of ETLs and a handy electron transport path for reducing the charge accumulation and series resistance of the cell. A top C-SnO 2 layer (regarded as an interlayer between Psk and Lt-TiO 2 :SnO 2 ) was used to extract/transport electrons facilely, to form a bilayered ETL with a cascade CB, and to create a hydrophilic surface to deposit high-quality Psk films to enhance the photovoltaic performance of the PSCs. This study provides a blueprint for designing good-performance ETLs for high-efficiency, stable regular planar PSCs using various sized nanoparticles prepared in a very simple and low-cost way.

The quality of the perovskite absorber is known to be the most crucial parameter for the photovoltaic performance of perovskite solar cells. By combining the one-step anti-solvent engineering method followed by gas blowing, MAPbI 3 film containing highly oriented multi-crystalline nanograins (150∼500 nm) was made first. A user-friendly, simple, large-throughput, and reproducible post-solvent annealing (made by treating the film with anti-solvent containing H 2 O under spinning) was used to enlarge the perovskite grains up to 1.5 μm. Inverted (p-i-n) perovskite solar cells based on this highly ordered, large-grain MAPbI 3 film achieve the highest efficiency of 21% with an extremely high fill factor (FF) of 86%. The high-efficiency cell shows almost no current hysteresis and is stable under 1 sun illustration in a glovebox or standing in the ambient atmosphere (20∼25 °C, ca. 30% humidity) under room lighting (T5 lamp, 500 lux). A creative method combining the gas blowing with quick and simple post-treatment to prepare a highly oriented MAPbI 3 film with large multi-crystalline grains to achieve excellent photovoltaic performance was demonstrated. This creative film-preparation method was also successfully applied to fabricate large area MAPbI 3 film for high-efficiency perovskite mini-modules. Being able to control the crystallization and growth of perovskite crystallites definitely makes the fabrication of perovskite solar cells more reproducible.

A high open-circuit voltage inverted perovskite solar cell based on a CH3NH3PbBr3 absorber and ICBA acceptor is reported. The CH3NH3PbBr3 film fabricated under ambient atmosphere at a moderate temperature (∼100 °C) using a two-step spin-coating method is composed of aggregated nano-grains. Upon solvent annealing of the CH3NH3PbBr3/ICBA film, the efficiency of the resulting cell increases from 1.71% to 7.50% with a remarkably high open circuit voltage (Voc) of ca. 1.60 V. ICBA acts not only as a high LUMO acceptor to realize high Voc but also as a mending agent to increase the efficiency of the cell by penetrating into the defects/voids of the CH3NH3PbBr3 film via solvent annealing as evidenced by TRPL, XPS and SEM data. Solvent annealing of the active layer was proved to be simple and effective device engineering to improve the efficiency of the perovskite cell based on a low quality film and the Voc of the inverted perovskite cell can be tuned by the LUMO level of the acceptor were revealed. The CH3NH3PbBr3/ICBA film is semi-transparent with an average 50% transmittance under visible light. The moderatetemperature processed CH3NH3PbBr3 solar cell with high Voc and a semi-transparent absorber has great potential for application as the top cell in a tandem solar cell.

The refractive index and extinction coefficient of a triiodide perovskite absorber (TPA) were obtained by fitting the transmittance spectra of TPA/PEDOT:PSS/ITO/glass using the transfer matrix method. Cu nanoplasmonic structures were designed to enhance the exciton generation in the TPA and to simultaneously reduce the film thickness of the TPA. Excitons were effectively generated at the interface between TPA and Cu nanoparticles, as observed through the 3D finite-difference time-domain method. The exciton distribution is advantageous for the exciton dissociation and carrier transport.

Broadband exciton dynamics in P3HT:PCBM blended film was observed by the femtosecond time-resolved photoluminescence sum-frequency technique. Onsager-Braun theory is applied to analyze the distribution of charge transfer radius at different energy levels. In our evaluation, the optimal diameter of P3HT fiber is about 14.3 nm for achieving the best exciton dissociation in P3HT:PCBM blended films. This technique can be readily used in the optimization of high-efficiency organic photovoltaics.

The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Friction Nanolithography (FRNL) is used to fabricate polyaniline nano-wire on a flexible, insulating, and highly transparent substrate. FRNL uses SPM tip to scratch the substrate to form a trench with higher friction force. Polyaniline nano-wire is selectively deposited on the trench. Sub-100 nm polyaniline wire is fabricated based on FRNL.

High conducting polyaniline films were readily prepared by in situ chemical oxidative polymerization/deposition of aniline in the presence of a very small amount of organic additive such as phenol. The conductivity of a thin ( approximately 150 nm) polyaniline film synthesized in the presence of 0.01 wt % of phenol ( r-PANI) is an order of magnitude higher (as well as better conducting homogeneity) than that of a film (PANI) obtained from the conventional method without an additive. r-PANI also has better adhesion and electrochemical stability/reversibility, more transparency in the visible-light region, and faster/easier doping/dedoping response compared to PANI. The function of phenol molecule is to avoid the formation of the inter- and/or intrachain hydrogen bonding during the growth of the polyaniline chains. The deaggregation/reducing intrachain hydrogen bonding of polyaniline chains by phenol molecules was revealed with IR, SAXS, and SEM data. All these data supported that phenol does assist the deaggregation of polyaniline chains during the growth of polymer chains or nanorods.