Progress and Future Prospects of Wide‐Bandgap Metal‐Compound‐Based Passivating Contacts for Silicon Solar Cells

Abstract

Figure 8. a) Dependence of work function on the energy gap of practical used TCO materials. b,c) Work function (○), carrier concentration (▫) and bandgap energy (Δ) as function of In 2 O 3 content for ZnO-In 2 O 3 film (b), SnO 2 content for In 2 O 3 -SnO 2 films (c). a-c) Reproduceded with permission. [91] Copyright 1998, Elsevier.

Perovskite‐Based Electron‐Selective Contacts for Silicon Solar Cells

“…Combining with low-WF metals, they can form excellent ihmic contacts with c-Si, making photogenerated electrons collected efficiently.Despite the successful demonstration of carrier selectivity, it is widely accepted that environmental and thermal stability remains one of the challenges for dopant-free contacts to be considered for industrial adoption. [20][21][22][23][24] A lot of dopant-free contacts are found to be sensitive to air exposure, especially when combined with heating, leading to the degradation of solar cell performance. [24][25][26][27][28][29] For example, ρ c of KF x /Al and CsF x /Al increase by more than one order of magnitude when exposed to air for 1000 h. [14] Furthermore, the V OC and FF of the c-Si solar cell using ZnO/LiF/Al as the electron-selective contact decrease from 727 mV and 78% to 428 mV and 46.5% within 75 h because of the interaction of ZnO/LiF/Al stack with air.…”

SiNx and AlOx Nanolayers in Hole Selective Passivating Contacts for High Efficiency Silicon Solar Cells

“…We have shown that nanolayers, 1-3 nm in thickness, of PECVD SiNx and ALD AlOx can be fabricated and produce low resistivity tunnelling contacts below 100 mΩ·cm 2 . Similar dielectrics have also been investigated in both DFPC and poly-Si contact structures [10], [37], [44], [65] This section discusses other works reported as a comparison to the results presented in Section III. There are two main types of contact structures, dopant free passivating contacts and poly-Si contacts.…”

“…There are two main types of contact structures, dopant free passivating contacts and poly-Si contacts. DFPC structures have been reported with 𝜌 𝑐 typically between 30-200 mΩ·cm 2 [10]. The structures most commonly use metal oxides which have a negative valence band offset so thicker layers can be used and still maintain low contact resistivity.…”

“…They consist of an interlayer, or layer stack, placed between the silicon and metal, which reduces the defect density while allowing the flow of carriers across them and thus maintaining a low contact resistivity. Multiple structures have been developed to achieve this, including poly-Si based contacts often referred to as tunnel oxide passivating contacts (TOPCon) [7] or poly-Si on oxide (POLO) [8], heterojunction technology (HJT) [9], and dopant free passivating contacts (DFPCs) [10]. The highest efficiencies achieved for double-side-contacted cells are 26.3% for HJT [11], 26.0% for poly-Si [12], and 23.5% for a DFPC hole contact with an n + a-Si layer as the electron contact [10].…”

“…Multiple structures have been developed to achieve this, including poly-Si based contacts often referred to as tunnel oxide passivating contacts (TOPCon) [7] or poly-Si on oxide (POLO) [8], heterojunction technology (HJT) [9], and dopant free passivating contacts (DFPCs) [10]. The highest efficiencies achieved for double-side-contacted cells are 26.3% for HJT [11], 26.0% for poly-Si [12], and 23.5% for a DFPC hole contact with an n + a-Si layer as the electron contact [10]. The key performance criteria for passivating contacts are: (i) low resistivity to maximise the fill factor of the device, (ii) good passivation to maximise the open circuit voltage, (iii) high transparency to minimise parasitic absorption, and (iv) competitive manufacturing cost versus current technologies.…”