HJT Solar Cell Layered Doping for Passivation and Carrier Transport
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Solution Overview
Problem
Existing HJT cells face challenges in passivation characteristics of the amorphous silicon layer and carrier transport, affecting photoelectric conversion efficiency.
Innovation Solution
A HJT cell structure with N-type crystalline silicon wafers, intrinsic amorphous silicon layers, SiO2 and C-doped SiO2 layers, and doped P-type and N-type amorphous silicon layers, including a double-layer stacked P-type structure doped with TMB and B2H6 gas, forms good electrical contact and passivation, enhancing light absorption and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-layer doped amorphous silicon structure is used, then the manufacturing process is simpler, but the photoelectric conversion efficiency is insufficient due to poor passivation characteristics and carrier transport
Solution Approach 1:
The patent divides the doped amorphous silicon layer into multiple layers with different doping types (P-type and N-type) and doping concentrations. Each layer serves specific functions: some layers provide passivation while others facilitate carrier transport. This segmentation resolves the contradiction by achieving high photoelectric conversion efficiency through functional differentiation without excessive complexity
Solution Approach 2:
Different regions of the amorphous silicon structure are assigned different doping characteristics. For example, layers closer to the intrinsic amorphous silicon have lower doping concentrations for better passivation, while layers closer to the TCO conductive layer have higher doping concentrations for better electrical contact. This local quality differentiation optimizes both passivation and carrier transport in their respective regions
2Reliability
If heavily doped amorphous silicon layer is used to improve electrical contact, then conductivity increases, but light absorption decreases due to reduced transparency
Solution Approach 1:
The patent applies different doping concentrations at different locations within the amorphous silicon structure. Layers requiring good electrical contact with TCO are heavily doped, while layers requiring light transmission are lightly doped or intrinsic. This spatial variation in doping quality resolves the contradiction between conductivity and light absorption
Solution Approach 2:
The amorphous silicon structure is segmented into multiple layers with graded doping concentrations. The segmentation allows the system to achieve both good electrical contact (through heavily doped layers) and adequate light absorption (through lightly doped or intrinsic layers), with each segment optimized for its specific function
3Productivity
If high doping concentration is used to improve carrier transport, then electrical conductivity improves, but interface passivation performance deteriorates
Solution Approach 1:
The patent segments the amorphous silicon into multiple layers with different doping concentrations. Intrinsic or lightly doped layers are positioned where interface passivation is critical, while heavily doped layers are positioned where carrier transport is prioritized. This segmentation allows simultaneous optimization of both passivation and carrier transport
Solution Approach 2:
Different regions of the amorphous silicon structure have different doping qualities tailored to local requirements. Regions at interfaces with intrinsic amorphous silicon use low doping concentrations for passivation, while regions at interfaces with TCO conductive layers use high doping concentrations for carrier extraction. This local quality differentiation resolves the contradiction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure improves open-circuit voltage, short-circuit current, and fill factor, increasing photoelectric conversion efficiency to 24.3% or more.
Implementation Method 1
the low temperature process ensures less interface damage to the monocrystalline silicon substrate. Meanwhile, the existence of an intrinsic layer gives rise to a better interface passivation performance
Implementation Method 2
forming an intrinsic amorphous silicon layer or a hydrogenated intrinsic amorphous silicon film layer on both sides of the N-type crystalline silicon wafer by plasma enhanced chemical vapor deposition
Implementation Method 3
Heterojunction solar cells maintain the core advantage of high efficiency due to a large forbidden band width of the heterostructure
Data Source
Figure 1
AI summary
The present application discloses a HJT cell having high photoelectric conversion efficiency and a method for preparing the same, which belongs to the field of solar cell technology. The HJT cell of this application includes an N-type crystalline silicon wafer. An intrinsic amorphous silicon layer, a SiO2 layer, a C-doped SiO2 layer, a doped N-type amorphous silicon layer, a TCO conductive layer and an electrode are sequentially disposed on a front surface of the N-type crystalline silicon wafer. An intrinsic amorphous silicon layer, a SiO2 layer, a C-doped SiO2 layer, a doped P-type amorphous silicon layer, a TCO conductive layer and an electrode are sequentially disposed on a back surface of the N-type crystalline silicon wafer. The doped P-type amorphous silicon layer includes a lightly B-doped amorphous silicon layer and a heavily B-doped amorphous silicon layer. The heterojunction solar cell made according to the present application increases the photoelectric conversion efficiency to more than 24.3%, and the short-circuit current and open-circuit voltage are improved significantly, which effectively increases the photoelectric conversion efficiency of the heterojunction silicon solar cell.