Search

A new class of fluorinated cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT)-based small molecules, namely YC-oF, YC-mF, and YC-H, are demonstrated as hole-transporting materials (HTMs) for high-performance perovskite solar cells (PSCs). PSCs employing YC-oF as the HTM delivered an excellent efficiency of 22.41% with encouraging long-term stability. [ABSTRACT FROM AUTHOR]

Organic small molecular materials with coplanar π-conjugated system as HTMs in perovskite solar cells (PSCs) have attracted considerable attention due to their high charge transport capability and thermal stability. Herein, three novel pentafulvalene-fused derivatives with or without fluorine atoms incorporated (YSH-oF and YSH-mF and YSH-H, respectively) are designed, synthesized, and applied as hole-transporting materials (HTMs) in PSCs fabrication. The fluorinated HTMs, YSH-oF and YSH-mF, exhibited higher hole mobility and better charge extraction at the perovskite/HTM interface than non-fluorinated one do, presumably due to the closer intermolecular π-π packing interactions. As a result, small-area (0.09 cm2) PSCs made with YSH-oF and YSH-mF achieved an impressive power conversion efficiency (PCE) of 23.59% and 22.76% respectively, with negligible hysteresis, in contrast with the 20.57% for the YSH-H-based devices. Furthermore, for large-area (1.00 cm2) devices, the PSCs employing YSH-oF exhibited a PCE of 21.92%. Moreover, excellent long-term device stability is demonstrated for PSCs with F-substituted HTMs (YSH-oF and YSH-mF), presumably due to the higher hydrophobicity. This study shows the great potential of fluorinated pentafulvalene-fused materials as low-cost HTM for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

In this work, we have successfully synthesized 15 new examples (LLA01‐06; LinLi01‐10) of small‐molecule hole‐transporting materials (HTM) using the less explored indolocarbazole (ICbz) as core moiety. Different from previously reported ICbz HTMs, LinLi01‐10 exhibit new molecular designs in which 3,4‐ethylenedioxythiophene (EDOT) units are inserted as crucial π‐spacers and fluorine atoms are introdcued into end‐group molecules. These substantially improve the materials solubility and device power conversion efficiencies (PCEs) while fabricated in perovskite solar cells (PSC). More importantly, LinLi01‐10 are generated by a sustainable synthetic approach involving the use of straightforward C−H/C−Br couplings as key transformations, thus avoiding additional synthetic transformations including halogenation and borylation reactions called substrate prefunctionalizations usually required in Suzuki reactions. Most HTM molecules can be purified simply by reprecipitations instead of conducting column chromatography. In contrast to LLA01‐06 without additional EDOT moieties, PSC devices using LinLi01‐10 as hole‐transport layers display promising PCEs of up to 17.5 %. Interestingly, PSC devices employing seven of the LinLi01‐10 as hole‐transport molecules, respectively, are all able to show an immediate >10 % PCE (t=0) without any device oxidation/aging process that is necessary for the commercial spiro‐OMeTAD based PSCs. [ABSTRACT FROM AUTHOR]

Abstract: The present study focuses on enhancing the efficiency of bifacial and back-illuminated dye-sensitized solar cells (DSCs) by incorporating SiO2 mesoporous layer on TiO2 electrode. The performance of DSCs is investigated by UV–visible spectroscopy, incident photon conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS). It is observed that the current ratio of back- to front-DSC increases with the increase in the thickness of SiO2 layer, which in turn influences the incident light to dyed-TiO2 electrode, especially in the wavelength of 400–600 nm. The Ti foil based flexible small (0.28 cm2) and sub-module (5 cm × 10 cm) DSCs having this modification show high conversion efficiencies of 6.76 and 5.54% respectively under 100 mW cm−2 (AM 1.5). [Copyright &y& Elsevier]

This paper presents a synchronous 50% duty-cycle clock generator (DCCG). The proposed DCCG circuit comprises of a clock generator and a phase error integrator. The clock generator is edge-triggered by an input signal to produce an output whose pulse width is determined by a delay line. The delay line is controlled by the phase error integrator which detects the phase difference between the input and output signals. The proposed DCCG is designed such that when the phase error is zeroed, i.e., the input and output signals are synchronized, the delay is properly adjusted and the output signal duty cycle converges to 50%. The proposed DCCG is implemented in a 0.35-\mum CMOS process. The circuit can operate from 70 to 500 MHz, and accommodates a wide range of input duty cycle ranging from 5% to 95%. The duty-cycle error of the output signal is less than 1.5%. Operated from a 3.3-V supply voltage, this circuit dissipates 7 mA at 500 MHz. [ABSTRACT FROM PUBLISHER]

This study improved quality of CH3NH3PbI3 (MAPbI3) perovskite films by delaying thermal annealing in the spin coating process and introducing KI and I2 to prepare MAPbI3 films that were low in defects for high-efficiency perovskite solar cells. The influences of delayed thermal annealing time after coating the MAPbI3 perovskite layer on the crystallized perovskite, the morphology control of MAPbI3 films, and the photoelectric conversion efficiency of solar cells were investigated. The optimal delayed thermal annealing time was found to be 60 min at room temperature. The effect of KI/I2 additives on the growth of MAPbI3 films and the corresponding optimal delayed thermal annealing time were further investigated. The addition of KI/I2 can improve perovskite crystallinity, and the conductivity and carrier mobility of MAPbI3 films. Under optimized conditions, the photoelectric conversion efficiency of MAPbI3 perovskite solar cells can reach 19.36% under standard AM1.5G solar illumination of 100 mW/cm2. [ABSTRACT FROM AUTHOR]

Abstract: The ionic conductivities and performances of dye-sensitized solar cells (DSSCs) of gel polymer electrolytes (GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent ((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO2 electrode not only reduced dye aggregation, but also reacted with the cross-linkers in the GPE at the TiO2/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of J SC significantly increased from 7.72 to 10.00mAcm−2. In addition, in order to reduce the ionic diffusion resistance within the TiO2 electrode, incorporation of monodispersed PMMA in the TiO2 paste was considered. With the optimal weight ratio of PMMA/TiO2 (w/w=3.75), the TiO2 electrode exhibited larger pores (ca. 350nm) uniformly distributed after sintering at 500°C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100mWcm−2, an improvement of ca. 55%. [Copyright &y& Elsevier]