Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

Abstract

High carrier recombination loss at the contact regions has become the dominant factor limiting the power conversion efficiency (PCE) of crystalline silicon (c‐Si) solar cells. Dopant‐free carrier‐selective contacts are being intensively developed to overcome this challenge. In this work, vanadium oxide (VOx) deposited by atomic layer deposition (ALD) is investigated and optimized as a potential hole‐selective contact for c‐Si solar cells. ALD VOx films are demonstrated to simultaneously offer a good surface passivation and an acceptable contact resistivity (ρc) on c‐Si, achieving a best contact recombination current density (J0) of ≈40 fA cm−2 and a minimum ρc of ≈95 mΩ.cm2. Combined with a high work function of 6.0 eV, ALD VOx films are proven to be an effective hole‐selective contact on c‐Si. By the implementation of hole‐selective VOx contact, the state‐of‐the‐art PCE of 21.6% on n‐type c‐Si solar cells with a high stability is demonstarted. These results demonstrate the high potential of ALD VOx as a stable hole‐transport layer for photovoltaic devices, with applications beyond c‐Si, such as perovskite and organic solar cells.

Dopant‐Free Bifacial Silicon Solar Cells

“…Therefore, extensive efforts have been devoted to the improvement of silicon solar cells with dopant‐free passivating contacts. [ 4–9 ] By replacing a‐Si:H(p) with a 4 nm thick hole‐collecting and transparent molybdenum oxide (MoO x ) layer, a remarkable solar cell efficiency of 23.5% was recently demonstrated. [ 10 ] The integration of an a‐Si:H(i)/LiF x /Al electron selective contact at the rear side, instead of a‐Si:H(i)/ a‐Si:H(n)/ITO/Ag, [ 11 ] enabled the development of a fully dopant‐free silicon solar cell without any doped a‐Si:H layers or diffused p–n junctions.…”

Solution‐Processed Copper‐Doped Chromium Oxide with Tunable Oxygen Vacancy for Crystalline Silicon Solar Cells Hole‐Selective Contacts

“…Transition metal oxides (TMOs) have been widely used as hole or electron selective transporting layers in crystalline silicon (c‐Si) solar cells to reduce the Fermi‐level pinning effect and to extract holes or free electrons in silicon at metal/silicon interface. [ 1–5 ] TMOs with high work functions (generally over 5.0 eV), such as MoO x , [ 6–10 ] VO x , [ 11,12 ] and WO x , [ 13 ] are applied as hole‐selective transporting layers. In contrast, TMOs with low work functions (generally below 4.0 eV), such as TiO x [ 14 ] and MgO x , [ 15,16 ] are applied as electron‐selective transporting layers.…”

Electron‐Selective ‍Lithium Contacts for Crystalline Silicon Solar Cells

“…Specifically, low‐workfunction metal oxides, nitrides, and 2D materials, such as TiO 2 , TaO x , ZnO, TaN x , TiN, and MXenes have been reported as electron‐selective layers (ESLs), and high‐workfunction MoO x and VO x have been developed as hole‐selective layers (HSLs) for c‐Si solar cells. [ 5,10–22 ] The band energetics of these thin films play a crucial role in achieving carrier selectivity of the contacts. Generally, the work function of the ESL in an electron‐selective contact is required to be close to or lower than the conduction band minimum (CBM) of c‐Si (≈4.05 eV, relative to the vacuum level).…”