Deng Youjun

A new improved structure of dye-sensitized solar cells with reflection film

A new improved structure of dye-sensitized nanocrystalline solar cells (DSSC) for utilizing reflected light was introduced in this paper. Typical DSSC is based on a sandwich structure, which consists of photoanode, electrolyte and cathode. For the improved structure of DSSC in this paper, a sliver reflection film was attached to the back of transparent conducting glass of cathode. In this way, the residual light passing through photoanode was reflected to it to be used again. The photocurrent-voltage characteristics of DSSC fabricated by two different thickness of TiO2 film were measured to illustrate the effects of utilizing reflected light. As a result, the improved DSSC with reflection film exhibited higher photocurrent and solar-to-electric conversion efficiency than DSSC without reflection film.

Study on device simulation and performance optimization of the epitaxial crystalline silicon thin film solar cell

Because crystalline silicon thin film (CSiTF) solar cells possess the advantages of crystalline silicon solar cells such as high efficiency and stable performance and those of thin film solar cells such as low cost and so on, it is regarded as the next generation solar cell technology, which is most likely to replace the existing crystalline silicon solar cell technology. In this paper, we performed device simulation on the epitaxial CSiTF solar cell by using PC1D software. In order to make simulation results closer to the actual situation, we adopted a more realistic device structure and parameters. On this basis, we comprehensively and systematically investigated the effect of physical parameters of back surface field (BSF) layer, base and emitter, electrical quality of crystalline silicon active layer, situation of surface passivation, internal recombination and p-n junction leakage on the optoelectronic performance of the epitaxial CSiTF solar cell. Among various factors affecting the efficiency of the epitaxial CSiTF solar cell, we identified the three largest efficiency-affecting parameters. They are the base minority carrier diffusion length, the diode dark saturation current and the front surface recombination velocity in order. Through simulations, we found that the base is not the thicker the better, and the base minority carrier diffusion length must be taken into account when determining the optimal base thickness. When the base minority carrier diffusion length is smaller, the optimal base thickness should be less than or equal to the base minority carrier diffusion length; when the base minority carrier diffusion length is larger, the base minority carrier diffusion length should be at least twice the optimal base thickness. In addition, this paper not only illustrates the simulation results but also explains their changes from the aspect of physical mechanisms. Because epitaxial CSiTF solar cells possess a device structure that is similar to crystalline silicon solar cells, the conclusions drawn in this paper are also applied to crystalline silicon solar cells to a certain extent, particularly to thin silicon solar cells which are the hottest research topic at present.

Selected area laser-crystallized polycrystalline silicon thin films by a pulsed Nd:YAG laser with 355 nm wavelength

Selected area laser-crystallized polycrystalline silicon (p-Si) thin films were prepared by the third har- monics (355 nm wavelength) generated by a solid-state pulsed Nd:YAG laser. Surface morphologies of 400 nm thick films after laser irradiation were analyzed. Raman spectra show that film crystallinity is improved with in- crease of laser energy. The optimum laser energy density is sensitive to the film thickness. The laser energy density for efficiently crystallizing amorphous silicon films is between 440-634 mJ/cm 2 for 300 nm thick films and be- tween 777-993 mJ/cm 2 for 400 nm thick films. The optimized laser energy density is 634, 975 and 1571 mJ/cm 2 for 300, 400 and 500 nm thick films, respectively.