钙钛矿太阳能电池稳定性的研究进展

回顾了钙钛矿太阳能电池的发展历程,总结了影响钙钛矿太阳能电池稳定性的几个重要因素,包括水汽、氧气、光照和高温条件对钙钛矿层的化学稳定性以及电子传输层(ETL)、空穴传输层(HTL)和制备工艺对电池稳定性的影响。对稳定机制进行了分析,提出了改善稳定性的一些方法,并根据目前的研究成果展望了钙钛矿太阳能电池的发展趋势。     

Photo-assisted Cl doping of SnO2 electron transport layer for hysteresis-less perovskite solar cells with enhanced efficiency

Developing efficient electron transport layers(ETLs)along with proper interface engineering is crucial to achieve high-performance perovskite solar cells(PSCs).Herein,a photo-assisted doping strategy was developed to modify SnO₂ETLs with Cl^-for efficient PSCs.The Cl^-modified SnO2(Cl^-SnO₂)with passivated surface defects as ETL material favors the formation of high phase-purity perovskite films and promotes the electron collection across the SnO₂/perovskite interface.Consequently,the efficiency of PSC is improved from 16.35%without Cl modification to 18.94%with the Cl modification,with little hysteresis and high stability.     

An optimized multilayer structure of CdS layer for CdTe solar cells application

CdS layers grown by ‘dry’ (close space sublimation) and ‘wet’ (chemical bath deposition) methods are deposited and analyzed. CdS prepared with close space sublimation (CSS) has better crystal quality, electrical and optical properties than that prepared with chemical bath deposition (CBD). The performance of CdTe solar cell based on the CSS CdS layer has higher efficiency than that based on CBD CdS layer. However, the CSS CdS suffers from the pinholes. And consequently it is necessary to prepare a 150 nm thin film for CdTe/CdS solar cell. To improve the performance of CdS/CdTe solar cells, a thin multilayer structure of CdS layer (∼80 nm) is applied, which is composed of a bottom layer (CSS CdS) and a top layer (CBD CdS). That bi-layer film can allow more photons to pass through it and significantly improve the short circuit current of the CdS/CdTe solar cells.     

Impact of donor, acceptor, and blocking layer thickness on power conversion efficiency for small-molecular organic solar cells

We investigated the dependency of the power conversion efficiency on the thickness of donor (copper phthalocyanine; CuPc), acceptor (fullerene; C₆₀), and hole/exciton blocking (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; BCP) layers in the OPV devices fabricated with double small-molecular layers. The power conversion efficiency peaked at a specific layer thickness, 12.7 nm for the donor layer, 17.5 nm for the acceptor layer, and 8.0 nm for the hole/exciton blocking layer. This trend of power conversion efficiency was determined by short-circuit-current rather than open-circuit-voltage after light absorption. In addition, the donor layer thickness was more sensitive than the thickness of the acceptor or hole/exciton blocking layers in improving power conversion efficiency; i.e., 330% for the donor layer, 118% for the acceptor layer, and 112% for the hole/exciton blocking layers.     

Cross-linked graphene layer embedded carbon film prepared using electron irradiation in ECR plasma sputtering

A new path to prepare cross-linked graphene layers embedded carbon (GLEC) films has been reported by introducing electron irradiation during the mirror-confinement electron cyclotron resonance (ECR) plasma sputtering process. The electron irradiation in the ECR plasma was identified by using Langmuir single probe equipped with a designed simulated substrate and the irradiation mode was found to be controlled directly by altering the substrate bias voltage. Cross-linked GLEC film was prepared using the electron irradiation in the pressure of 0.04 Pa and positive bias voltage of 50 V, and the nanostructure and binding configuration of the film were analyzed by high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results showed that GLEC film contains cross-linked graphene layers grown normally to the substrate surface when the content of sp² hybridized carbon atoms in the film is more than 70%. The tribological behaviors of both cross-linked GLEC films and amorphous carbon films were compared using a Pin-on-Disk tribometer, and the mechanism for low friction coefficient was discussed by using HRTEM observation on wear track. The HRTEM results indicated that the cross-linked GLEC film has the potential to achieve low friction at the beginning of the friction.     

Gel electrolytes containing several kinds of particles used in quasi-solid-state dye-sensitized solar cells

Composite gel electrolytes containing several kinds of particles used as the quasi-solid-state electrolytes in dye-sensitized solar cells (DSSCs) were reported. Mesoporous particles (MCM-41) with unique structures composed of ordered nanochannels were served as a new kind of gelator for quasi-solid-state electrolytes. MCM-41, hydrophobic fumed silica Aerosil R972 and TiO2 nanopatricles P25 were dispersed into gel electrolytes respectively. The solar energy-to-electricity conversion efficiency of these cells is 4.65%, 6.85% and 5.05% respectively under 30 mW·cm-2 illumination. The preparation methods and the particles sizes exert an influence on the performance of corresponding solar cells. Owing to unique pore structures and high specific BET surface area, mesoporous silica MCM-41 was expected to have the potential to afford conducting nanochannels for redox couple diffusion.     

The double-edged function of UV light in polymer solar cells with an inverted structure

Inverted polymer solar cells with a configuration of ITO/ZnO/PBDTTT-C:PC₇₁BM/MoO₃/Ag were fabricated and a power conversion efficiency of 6.64% was achieved under AM 1.5G irradiation (89 mW/cm²). The function of UV light was systematically investigated by tracking the changes of the device performance for 212 min under continuous illumination with or without UV light. We found that UV light plays a decisive role not only in the photo-annealing step, leading to a remarkable increase of PCE by increasing ZnO conductance, but also in the photo-bleaching step, causing slow degradation of solar cells through photo-oxidation of the conjugated polymer.     

A novel microwave absorption and dielectric spectrum detection technology in photoelectron dynamic study for solar cells

The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence on the dielectric function of the solar cell material. And the amplitude variance of the imaginary andreal part of the dielectric function is in direct proportion to the dynamic process of free and shallow-trapped electrons. Based on the untouched detection technique, the method is present to detect the amplitude change of the microwave signal which is passing through the material whose dielectric function changes after exposure. A35GHz oscillator was used as a microwave source. The absorptionand dispersion microwave signals, which contain the dynamic information of free and shallow-trapped electron signal, are split respectively with phase-sensitive instrument. The photoelectron character of n-type Si(100) thin film was investigated by the novel equipment, and the lifetime of different kinds of electronswith the resolution of 1 ns was obtained. The equipment can be directly used inthe study of the optoelectronic conversion mechanism of solar cells.     

Effect of polyethyleneimine on the growth of ZnO nanorod arrays and their application in dye-sensitized solar cells

A series of oriented hexagonal wurtzite ZnO nanorod-array films were grown on fluorine-doped tin oxide (FTO) coated glass substrates by chemical process. The effect of polyethyleneimine (PEI) on the structure and micro-morphology of ZnO nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) was analyzed. It was found that with the addition of PEI in growth solution, the ZnO nanorods became smaller in diameter and longer in length and hence the dye absorption and the photovoltaic performance of DSSCs were improved. A power conversion efficiency of 2.30% had been achieved on a DSSC based on a 7.9 μm-long nanorod array film prepared by a growth solution containing the PEI.     

Role of PbO-based glass frit in Ag thick-film contact formation for crystalline Si solar cells

The reactions between Ag pastes containing two types of PbO-based glass frits and an n-type (100) Si wafer during firing in air at 800 °C were investigated in order to understand the mechanism for the formation of inverted pyramidal Ag crystallites at the Si interface as well as the effect of the PbO content of the glass frit on Ag crystallite formation. Inverted pyramidal Ag crystallites were formed by the precipitation of Ag atoms dissolved in fluidized glass during the subsequent cooling process after firing. PbO in the glass frit did not participate directly in the reaction with the Si wafer. However, its content had a strong influence on the reaction rate at the glass/Si interface and, thus, on the size and distribution of the Ag crystallites. The effect of the PbO content in the glass could be understood from the higher Ag solubility and lower viscosity of the glass at the firing temperature with increasing PbO content. Based on the experimental results, a model was proposed for the formation of Ag crystallites at the glass/Si interface during the firing process of screen-printed thick-film Ag metallization.     

Modification of poly(ethylene oxide) electrolyte by Brönsted base terminated oligo(ethylene glycol) and its application in dye-sensitized solar cells

Oligo(ethylene glycol) terminated by pyridine derivatives was designed and synthesized for improving the performance of the dye-sensitized solar cells (DSCs) with poly(ethylene oxide) based electrolyte. Effects of the plasticizer on retarding the recombination reaction in DSCs were characterized by current density–voltage characteristics. Combined with the results on electron density measurements, photovoltage–intensity characteristics correlate the retarded electron recombination with the upward movement of the conduction band edge and the reduced order of recombination reaction. The increased electron lifetimes of the DSCs with plasticizer modified electrolyte were confirmed by a small perturbation voltage decay technique. Additionally, WAXS measurements show that the presence of the plasticizer decreases the crystallinity of PEO electrolyte, which facilitates the mass transport of the redox species as impedance spectra indicated. By introducing guanidinium thiocyanate into the plasticizer modified PEO electrolyte, the performance of the DSCs is further improved, which yields the highest efficiency of 3.5%.     

Charge transport and recombination in dye-sensitized solar cells based on hybrid films of TiO2 particles/TiO2 nanotubes

In this paper, anodic TiO₂ nanotubes are blended into the TiO₂ mesoporous films based on P25 nanoparticles to assemble a list of dye-sensitized solar cells (DSSCs) with different nanotube concentrations. The electron properties of transport and recombination in the fabricated DSSCs are studied by using electrochemical impedance spectroscopy and the open-circuit voltage decay technique under AM 1.5 illumination. Results indicate that the electron lifetime increases with increasing the concentration of the anodic TiO₂ nanotubes, the electron transport time at a blending level of 10 wt% TiO₂ nanotubes is short as compared to that at 0 wt%, and above 10 wt%, the electron transport time has a trend of becoming large. Due to the combining effects of the electron transport and recombination, the electron collecting efficiency and the electron diffusion length obtain maxima at a blending level of 10 wt% nanotubes, which results in a highest short circuit current and a maximum energy conversion efficiency at this point in the DSSCs. This study gives a clear explanation for the performance enhancement of TiO₂ particle-based DSSCs at a blending level of 10 wt% anodic TiO₂ nanotubes and for the performance decrease at a blending level over 10 wt% anodic TiO₂ nanotubes from the angle of the electron transport and recombination. This study also supplies a feasible and easy way to improve the performance of particle-based DSSCs by restraining electron recombination and accelerating electron transportation.     

Enhancement of device efficiency in CuPc/C60 based organic photovoltaic cells by inserting an InCl3 layer

An InCl₃ dipole layer is inserted into a copper phthalocyanine (CuPc) and fullerene (C₆₀) based organic photovoltaic cell (OPV) to modify the indium-tin-oxide (ITO) anode surface. The work function of the ITO is improved from 4.63 eV to 5.47 eV. In addition, a 30% enhancement in absorption coefficient is achieved due to the strong interaction between CuPc and InCl₃ molecules, which induces a configuration change of the CuPc stacks from perpendicular to parallel along the ITO substrate. Therefore, the power conversion efficiency of the OPV devices has a 30% improvement because of the improved work function of the ITO anode and the enhanced absorption coefficient of the devices.     

Magonelli相二氧化钛光阳极在量子点敏化太阳能电池中的性能研究

使用产量与性能稳定的工业化生产的黑色二氧化钛制备成QDSSCs的光阳极,通过性能表征与理论计算研究,与常见的Anatase TiO2,Rutile TiO2展开了全面对比。结果表明,由于氧空位的引入导致Magonelli Ti8O15的导带底下降,带隙收缩,吸收光谱范围由紫外光扩展至可见光与近红外,而且吸光度也极大提高。其阻抗也随之减小,明显低于Anatase TiO2,Rutile TiO2。这导致其组装的QDSSCs的性能获得极大提升,尤其是FF与Jsc表现最为显著,最终获得了PCE 5.3%优异成绩。这项工作进一步丰富了黑色二氧化钛的研究,在工业化生产黑色二氧化钛组装太阳能电池领域取得了阶段性成果,为太阳能电池的生产提供了新的可能。