Figure 1. Schematic diagram of the structure of the perovskite type solar cell; (b) the perovskite energy level diagram at different silver injection ratios; and (c) the voltage-current efficiency curve of the perovskite device at different silver injection ratios.
Figure 2. (a) cross-sectional scanning of the Kelvin probe microscope to characterize the trans-structure of the organic solar cell level arrangement; (b) through the deconvolution algorithm to restore the device's true potential distribution.
In recent years, new thin film solar cells, such as organic / inorganic hybrid perovskite devices, organic photovoltaic devices, etc., with its low cost, high efficiency, simple structure, flexible carrying, etc., attracted wide attention.For thin film solar cells It is one of the important determinants of the performance of the device. How to effectively regulate and characterize the device level arrangement is to understand the device, Working mechanism, guiding material screening and device process optimization and other important entry point.
Recently, the Chinese Academy of Sciences, Suzhou Institute of nanotechnology and nano bionic researcher Chen Li mast task group in the thin film solar cell level arrangement regulation and characterization of two aspects of research progress:
1. In organic / inorganic hybrid perovskite photovoltaic devices, a deep understanding of material doping, energy level regulation and device performance interrelationship.First-principles calculations show that the metal ion outer electron orbitals is organic / inorganic hybrid Perovskite band structure of the important determinants, thereby affecting the optical and electrical properties of materials.Many research groups at home and abroad reported that a small amount of metal ions can replace Pb2 + can effectively improve device performance, but the evolution of the energy level structure and device performance The interaction mechanism of the lack of in-depth research.Chen Li mast use of Ag + part of the replacement of Pb2 + into the perovskite accept state, making the original n-type perovskite material Fermi level shift to the center of the band, presented this This kind of change can effectively reduce the electron concentration in the perovskite, which is beneficial to the balanced transport of carriers. By optimizing the silver doping ratio, the crystallinity of the perovskite material is improved and the morphology and current-carrying capacity of the film are improved In addition, the efficiency of the ITO / Cu: NiOx / perovskite / PCBM / Ag trans structure increased from 16.0% to 18.4% under the synergistic promotion of these factors (Figure 1) .Furthermore, The interaction between perovskite carrier concentration and device performance was confirmed by the equivalent circuit model, and the related research results were published in Nano Lett.
In the organic thin film photovoltaic device, the energy level arrangement of the trans device is quantitatively represented under the condition of the device.For the vertical closed structure of the thin film solar cell stacking layer, there is a lack of effective means to intuitively measure the device work The operability of the operando is reported in the Nat. Commun. Cross-sectional scanning of the cross-sectional SKPM, which allows for short circuit, open circuit, dark state, and lighting conditions And the quantitative measurement of energy level arrangement is still pending.Further study, Chen Li mast task group found that the tip / cantilever beam convolution effect is an important factor affecting the quantitative measurement of the device level structure, in the presence of interface (ITO / ZnO / BHJ / MoOx / Al) convolution effect can even cover the real potential distribution and get the built-in electric field with the wrong direction.In order to solve this problem, (Fig. 2) was used to reconstruct the true effect of the trans device (Fig. 2) by using the deconvolution algorithm to remove the average effect of the tip of the pin by using the GaAs / GaInP heterojunction of the molecular beam epitaxial growth. Research published in Nano Energy, and in the "Journal of Chemical Physics" written monographs.
The research work has been supported by Alex Jen, Professor of University of Washington, USA, and Professor Lu Shulong and Ma Changzhong, who are supported by the National Natural Science Foundation of China, the key research and development of the Ministry of Science and Technology, and the funding and R & D conditions of the Scientific Research Equipment Project of the Chinese Academy of Sciences.
