Heterojunction solar cell and manufacturing method thereof

Abstract

The invention provides a heterojunction solar cell. The heterojunction solar cell comprises a first film with a first conductivity type, an active region and a second film with a second conductivity type, wherein the active region and the second film are sequentially arranged on the surface of the first film; a contact layer which is heterogeneous with the first film and provided with the first conductivity type is arranged between the first film and the active region; the first film and the second film are respectively heterogeneous with the active region; and the active region has a structure of a gradient layer. The invention also provides the manufacturing method for the heterojunction solar cell. The manufacturing method comprises the following steps of: 1, growing the contact layer which is heterogeneous with the first film and provided with the same conductivity type as the first film on the naked surface of the first film; 2, epitaxially growing the active region with the gradient structure on the naked surface of the contact layer; and 3, growing the second film heterogeneous with the active region on the naked surface of the active region, wherein the conductivity types of the first film and the second film are opposite.

Description

technical field [0001] The invention relates to the field of solar cells, in particular to a heterojunction solar cell and a preparation method thereof. Background technique [0002] In x Ga 1-x The N band gap is adjustable within 0.7eV~3.4eV (corresponding to wavelength 354nm~1720nm), which is an important potential material for realizing full-spectrum solar cells in the future. However, P-N junction cells based on InGaN-based multi-junction and higher In composition are still difficult to realize due to the difficulty of P-type doping of high In composition InGaN and the efficiency limitation of single junction cells. Considering that the In composition of InGaN can be adjusted continuously, solar cells based on its graded structure have attracted much attention. [0003] The traditional solar cell preparation method based on the design idea of ​​InGaN active region, the brief steps are as follows: figure 1 , including: Step 100, growing a buffer layer 204 and an N-typ...

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Problems solved by technology

like figure 1 , Figure 2A , Figure 2B , Figure 2C and Figure 2D As shown, according to this method, during the growth process of the active region 202 of InGaN, a material with a large difference in lattice constant between the N-type and P-type GaN layers is directly grown. In the source region, a large number of misfit dislocations will appear due to stress release, such as Figure 2C As shown by the dislocation 208 in , which reduces the crystalline quality of the material and thus affects the performance of the solar cell

At the same time, due to the large material difference between the active region and the N-type and P-type GaN layers, the contact barrier is relatively high, such as the simplified energy band structure diagram of a traditional mismatched solar cell, namely Figure 5A , which is not conducive to the transport of carriers, which will reduce the efficiency of solar cells

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