Catalytic phosphorus and boron doping of amorphous silicon films for application to silicon heterojunction solar cells

Abstract

We investigate a novel doping method, catalytic impurity doping (Cat-doping), for application to the fabrication of silicon heterojunction (SHJ) solar cells. Thin n- or p-type doped layers can be formed on intrinsic amorphous Si (a-Si) films by exposing P- or B-related radicals generated by the catalytic cracking of phosphine (PH3) or diborane (B2H6) gas molecules. The passivation quality of underlying a-Si films can be maintained both for phosphorus (P) and boron (B) Cat-doping if we carefully choose the appropriate substrate temperature during Cat-doping. We confirm the rectifying and photovoltaic properties of an SHJ solar cell containing a B Cat-doped layer as a p-type a-Si emitter. These findings suggest the applicability of Cat-doping to SHJ solar cells.

Enhancing the Selectivity and Transparency of the Electron Contact in Silicon Heterojunction Solar Cells by Phosphorus Catalytic Doping

“…Former studies have shown that Catdoping can further improve the conductivity of silicon thin films compared to the values that is achievable for as-grown films, [28] or improve the passivation quality of SHJ structures with treating on different interfaces. [29,30] Primary results of applying Cat-doping on SHJ solar cells have also been demonstrated by Ohdaira et al [31] and Liu et al, [32] even though low efficiency was achieved and the limitations still need more investigation.…”

“…[ 29,30 ] Primary results of applying Cat‐doping on SHJ solar cells have also been demonstrated by Ohdaira et al. [ 31 ] and Liu et al., [ 32 ] even though low efficiency was achieved and the limitations still need more investigation.…”

Phosphorus Catalytic Doping on Intrinsic Silicon Thin Films for the Application in Silicon Heterojunction Solar Cells

“…Among many techniques to solve the aforementioned two problems, catalytic doping (Cat-doping) is a cheap, simple, and industrially feasible postdeposition doping method, which is based on the hot wire chemical vapor deposition (HWCVD) process . Doping gases, such as phosphine (PH 3 ) and diborane (B 2 H 6 ), are catalytically decomposed at the hot surface of the filaments into phosphorous (P) and boron (B) radicals. , The radicals move from the filament surface to the sample surface and then diffuse into the silicon material films, forming a shallow depth doping layer with a thickness of 5–20 nm. − Therefore, it is possible to replace the deposition of the doped silicon layer by Cat-doping on the intrinsic layer, which reduces the parasitic absorption of doped silicon layers. Former studies have shown that the material properties, such as conductivity and doping concentration, can be further tuned beyond the level that is achievable for as-grown films. ,, It has also been reported that the passivation quality of SHJ structures could be improved with Cat-doping on different interfaces, such as at the c-Si, a-Si:H­(i), and doped silicon layer surfaces in a SHJ structure. ,,,− …”

“…21 Doping gases, such as phosphine (PH 3 ) and diborane (B 2 H 6 ), are catalytically decomposed at the hot surface of the filaments into phosphorous (P) and boron (B) radicals. 22,23 The radicals move from the filament surface to the sample surface and then diffuse into the silicon material films, forming a shallow depth doping layer with a thickness of 5−20 nm. 23−25 Therefore, it is possible to replace the deposition of the doped silicon layer by Cat-doping on the intrinsic layer, which reduces the parasitic absorption of doped silicon layers.…”

Phosphorous Catalytic‐Doping of Silicon Alloys for the Use in Silicon Heterojunction Solar Cells

“…So far, cat-doping has been studied mainly on crystalline silicon, amorphous silicon, and microcrystalline silicon. [10,11,13,14] Former studies have shown that cat-doping can improve the conductivity of a-Si:H and μc-Si:H films. Cat-doping can also improve the passivation quality of the passivated samples with symmetric structures of μc-Si:H(n)/a-Si:H(i)/c-Si/a-Si:H(i)/ μc-Si:H(n) and a-Si:H(n)/a-Si:H(i)/c-Si/a-Si:H(i)/a-Si:H(n) in which the interfaces of μc-Si:H(n) and c-Si are cat-doped, respectively.…”