Photovoltaic and spectral properties of tetraphenyloporphyrin and metallotetraphenyloporphyrin dyes

Spectroscopical properties and photocurrent (or photovoltage) of tetraphenyloporphyrins and metallotetraphenyloporphyrins in nematic liquid crystal have been studied. Photoelectric response has been measured in an electrochemical cell made of the semitransparent semiconducting and golden electrodes with porphyrin dyes embedded in liquid crystal. Fluorescence, time-resolved luminescence in microsecond time scale and photoacoustic spectra have also been measured. The competition between radiative, non-radiative processes and charge transfer is discussed. It has been shown that effectivity of porphyrins for photocurrent generation depends on the presence/absence of central metal in the macrocycle of porphyrin skeleton and the kind of metal. The schematic model of the contributions of the dye molecule and semiconducting electrode in the electron transfer process is shown.     

Investigation of the electrical and optical properties of InAs/InGaAs dot in a well solar cell

The electroreflectance (ER) and current–voltage (J–V) of InAs/InGaAs dots in a well (DWELL) solar cell (SC) were measured to examine the optical and electrical properties. To investigate the carrier capturing and escaping effects in the quantum dot (QD) states the above and below optical biases of the GaAs band gap were used. In the reverse bias region of the J–V curve, the tunneling effect in the QD states was observed at low temperature. The ideality factors (n) were calculated from the J–V curves taken from various optical bias intensities (I_ex). The changes in the ideality factor (n) and short circuit current (J_SC) were attributed mainly to carrier capture at low temperature, whereas the carrier escaping effect was dominant at room temperature. ER measurements revealed a decrease in the junction electric field (F_J) due to the photovoltaic effect, which was independent of the optical bias source at the same temperature. At low temperature, the reduction of photovoltaic effect could be explained by the enhancement carrier capturing effect due to the strong carrier confinement in QDs.     

紫外光照处理对TiO2膜光伏性能的影响

近年来人们利用纳米晶TiO2电极取代普通的TiO2电极[1],使其太阳能电池的光电转换效率得到很大提高.纳米晶TiO2电极具有大量表面态,在化学上表现为Ti3+或Ti—OH,对于光生电荷的分离过程和迁移过程有重要影响.这些表面化学结构的变化可能会导致TiO2的光伏性能的变化.1997年Fujishima等[2]用紫外光照射TiO2膜使它具有超亲水的性质,结构分析表明,超亲水的原因在于光照使TiO2膜的表面形成Ti—OH[3].因此,在光照处理的同时可能会导致TiO2的光伏性的变化.本文对紫外光照处理TiO2膜的光伏性能进行了研究,并结合光诱导TiO2的亲水性变化对光伏性能变化的原因进行了讨论.     

外围缩合四个1,10-啡啰啉单元的新氮杂酞菁的表面光伏响应及电场作用研究

通过电场诱导表面光电压谱确定外围缩合4个1,10-啡啉单元的氮杂酞菁为p型有机半导体,并对各个谱带进行合理的归属.结果发现,Soret带长波侧光电压曲线在电场作用下轻微蓝移,根据电场对高极化度n轨道基态的影响,将其归属为n-π^*     

磺化酞菁铜分子膜／SiO2／Si界面电荷转移机制的研究

在具有不同氧化层厚度的p型硅基片上修饰2层磺化酞菁铜分子膜.利用时间分辨表面光电压谱技术,对该膜系的界面电荷转移机制的光电开关特性进行了研究。结果表明,用时间分辨表面光电压谱技术研究界面电荷转移过程具有明显优越性.     

Eu2O3纳米晶谱带特征及光伏性质的研究

利用表面光电压谱技术对不同粒径的Eu2O3纳米晶进行光吸收特性的研究，并结合紫外－可见反射吸收光谱对其谱带进行解析，实验发现，随着样品粒径的变小，部分f→f跃迁的吸收带明显增加强并发生红移；在300－500nm区间有一个宽吸收边带，此带可归属于O2p→Eu4f的电荷转移跃迁。     

Modification of n-Si(1 1 1) wafer with olefin carboxyl acids and olefin sulfite acids and the photovoltaic properties of the electrodes

n-Si(1 1 1) crystalline electrode was modified by carboxyl acid groups and sulfonic groups. The flat band potential (U_fb), relation between flat band potential and the carbon numbers to the modified samples and relation between photocurrent density and potential of the modified electrodes were studied. ATR-IR spectra and XPS analysis show that the organic compounds were connected to n-Si(1 1 1) wafer by SiC bond. Calculation indicates that the surface modification ratio increased with the carbon number of organic groups decreased. Mott-Schottky plots gives the flat band potential of the samples to shift to negative positions with the carbon number decreased in both of the two different systems and the flat band potential of the sample with the group of (CH₂)₃SO₃H reaches to −0.82 V, which is more negative than reported, and the flat band potential of all the samples in this paper are more negative than the sample with methyl group [B. Ashish, N.S. Lewis, J. Phys. Chem. B 102 (1998) 1067; S. Takabayashi, M. Ohashi, K. Mashima, Y. Liu, S. Yamazaki, Y. Nakato, Langmuir 21 (2005) 8832]. The photocurrent and photovoltage of the modifications are stable enough under solar illumination for a long time.     

A Study of Spectroscopy on TCAQ Microcrystal

UV-visible absorption spectra of 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) solution, crystal and evaporated film were, measured. The absorption spectrum of TCAQ solution in DMF had three bands at 287 nm(4.45), 310 nm(4.23) and 350 nm(4.38) respectively; that of evaporated films had one band at 370 nm and that of crystalline powder had four bands at 243 nm, 275 nm, 320 nm and 430 nm respectively. Surface photovoltage spectra of TCAQ microcrystal gave two bands at P₁ (320 nm) and P₂ (430 nm) respectively. The absorption bands were assigned and the energy levels of frontier orbitals were tentatively determined. In addition,the mechanism of hole, production and transportation in crystalline TCAQ was discussed.     

酞菁铜与Q-CdS超微粒子界面的光致电荷转移研究

半导体超微粒子与有机分子界面的光致电行转移过程是当前光化学和材料科学研究的一个活跃领域［‘，2］；研究的目的主要有两个方面，一是研究半导体超微粒子表面光致电行转移的特性；二是研究有机分子对超微粒子的光敏化作用．目前，超微粒子的功能化研究日益深入，其独特的光     

Subsurface Engineering Induced Fermi Level De-pinning in Metal Oxide Semiconductors for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is a promising approach for renewable solar light conversion. However, surface Fermi level pinning (FLP), caused by surface trap states, severely restricts the PEC activities. Theoretical calculations indicate subsurface oxygen vacancy (sub-O_v) could release the FLP and retain the active structure. A series of metal oxide semiconductors with sub-O_v were prepared through precisely regulated spin-coating and calcination. Etching X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and electron energy loss spectra (EELS) demonstrated O_v located at sub ∼2–5 nm region. Mott–Schottky and open circuit photovoltage results confirmed the surface trap states elimination and Fermi level de-pinning. Thus, superior PEC performances of 5.1, 3.4, and 2.1 mA cm⁻² at 1.23 V vs. RHE were achieved on BiVO₄, Bi₂O₃, TiO₂ with outstanding stability for 72 h, outperforming most reported works under the identical conditions.