Abstract
AbstractTraditional silicon solar cells extract holes and achieve interface passivation with the use of a boron dopant and dielectric thin films such as silicon oxide or hydrogenated amorphous silicon. Without these two key components, few technologies have realized power conversion efficiencies above 20%. Here, a carbon nanotube ink is spin coated directly onto a silicon wafer to serve simultaneously as a hole extraction layer, but also to passivate interfacial defects. This enables a low‐cost fabrication process that is absent of vacuum equipment and high‐temperatures. Power conversion efficiencies of 21.4% on an device area of 4.8 cm2 and 20% on an industrial size (245.71 cm2) wafer are obtained. Additionally, the high quality of this passivated carrier selective contact affords a fill factor of 82%, which is a record for silicon solar cells with dopant‐free contacts. The combination of low‐dimensional materials with an organic passivation is a new strategy to high performance photovoltaics.
Highlights
Traditional silicon solar cells extract holes and achieve interface passivation bound asymmetrically on either side by carrier selective contacts to provide a built in with the use of a boron dopant and dielectric thin films such as silicon oxide potential for electron/hole separation
In this work we show that combination of a low dimensional material (CNTs) and Nafion can be combined into an ink to form a “passivated charge selective contact” (PCSC) that can be spin coated directly onto crystalline silicon (c-Si)
Single walled carbon nanotubes (SWCNTs) with an average diameter of 1.5 nm and Nafion polymer were shear force mixed for 2 h to afford the CNT:Nafion ink used throughout this work, Figure 1a
Summary
Single walled carbon nanotubes (SWCNTs) with an average diameter of 1.5 nm and Nafion polymer were shear force mixed for 2 h to afford the CNT:Nafion ink used throughout this work, Figure 1a. Spin coating of the CNT:Nafion ink enables its direct industrialization Using this approach device fabrication consisted of only six main steps: silicon surface texturing; front phosphorus diffusion; SiNx deposition; screening printing of the front fingers; CNT:Nafion coating and Ag metallization on the back. The simplicity of this approach rivals that of the Al-BSF cell as shown, where a direct comparison is made. A highly spatial resolution of photoluminescence (PL) mapping was performed on the 245.71 cm industrial size solar cell, as shown, except for some places of contamination during fabrication, a homogenous contrast throughout all measurements can be regarded as the evidence of minimal variation of the CNT:Nafion film composition A highly spatial resolution of photoluminescence (PL) mapping was performed on the 245.71 cm industrial size solar cell, as shown in Figure 4c, except for some places of contamination during fabrication, a homogenous contrast throughout all measurements can be regarded as the evidence of minimal variation of the CNT:Nafion film composition
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