Pyramid size control and morphology treatment for high-efficiency silicon heterojunction solar cells

Abstract

This paper investigates the formation process of surface pyramid and etching characteristics during the texturing process of mono-crystalline silicon wafers. It is found that there is an etch rate transition point in alkaline anisotropic etching when {100} plane-dominated etch turns to {111} plane-dominated etch, and the pyramid size has a strong linear correlation with the etch amount at the transition point. Several techniques were developed to control the pyramid size by monitoring and adjusting the etching amount. A wide range of average pyramid sizes were successfully achieved, from 0.5 to 12 μm. The experiments of the pyramid size on the light reflectance, the minority carrier lifetime (MCLT), and the performance of silicon heterojunction (SHJ) solar cells were carried out and analyzed. A desirable range of pyramid sizes was empirically determined by our investigation. In order to reduce the density states on the texturing surface, the wet-chemical smoothing treatment was also investigated. The smoothing treatment improves the passivation quality and the performance of the solar cells. Through pyramid size control and morphology treatment, together with the amorphous silicon (a-Si:H) deposition improvement, and electrode optimization, high performance of SHJ solar cells has been achieved, up to conversion efficiency 23.6%.

Micro/Nanostructures for Light Trapping in Monocrystalline Silicon Solar Cells

“…Micronanomanufacturing technology is the key to realizing that artificial antireflection nanostructures can be applied to silicon solar cells. Because Si has an appropriate hardness and is easy to react with acids and alkaline, almost all kinds of nanomanufacturing technologies we know can be used to manufacture antireflection micron/nanostructures on the silicon surface, including wet etching [55][56][57], dry etchings [58,59], nanoimprinting [60,61], and laser interference lithography [62,63]. Because these nanomanufacturing technologies have different characteristics, appropriate manufacturing technologies should be selected according to the shape, size, and pattern of nanostructures, and a variety of nanomanufacturing technologies are usually required to be combined to manufacture nanostructures with complex shapes and periodic arrangements.…”

Polarizable High‐Index Nanoparticles Used for Light‐Induced Crystal‐Silicon Passivation and Dielectric Antenna for High‐Efficiency Solar Cell

“…In contrast, the latter is a technique to alleviate the carrier density at the solid surface through an electric field induced by fixed charges. The dopants in the heterojunction contact structure are strictly limited to the outer a‐Si:H layers, requiring stringent passivation arising from the intrinsic a‐Si:H. [ 5,6 ] The induced surface potential in the c‐Si wafer therefore is fundamental in the heterojunction structure. [ 7,8 ]…”

“…In contrast, the latter is a technique to alleviate the carrier density at the solid surface through an electric field induced by fixed charges. The dopants in the heterojunction contact structure are strictly limited to the outer a-Si:H layers, requiring stringent passivation arising from the intrinsic a-Si:H. [5,6] The induced surface potential in the c-Si wafer therefore is fundamental in the heterojunction structure. [7,8] In heterojunction c-Si solar cells, deleterious interfacial defect densities can be effectively alleviated by the a-Si:H layer, leading to excellent interface passivation quality and rational band bending.…”