V₂O_x-based hole-selective contacts for c-Si interdigitated back-contacted solar cells

Abstract

Over the last few years, transition metal oxide layers have been proposed as selective contacts both for electrons and holes and successfully applied to silicon solar cells. However, better published results need the use of both a thin and high quality intrinsic amorphous Si layer and TCO (Transparent Conductive Oxide) films. In this work, we explore the use of vanadium suboxide (V2Ox) capped with a thin Ni layer as a hole transport layer trying to avoid both the intrinsic amorphous silicon layer and the TCO contact layer. Obtained figures of merit for Ni/V2Ox/c-Si(n) test samples are saturation current densities of 175 fA cm-2 and specific contact resistance below 115 mO cm2 on 40 nm thick V2Ox layers. Finally, the Ni/V2Ox stack is used with an interdigitated back-contacted c-Si(n) solar cell architecture fully fabricated at low temperatures. An open circuit voltage, a short circuit current and a fill factor of 656 mV, 40.7 mA cm-2 and 74.0% are achieved, respectively, leading to a power conversion efficiency of 19.7%. These results confirm the high potential of Ni/V2Ox stacks as hole-selective contacts on crystalline silicon photovoltaics.Peer ReviewedPostprint (published version

Stable Dopant-Free Asymmetric Heterocontact Silicon Solar Cells with Efficiencies above 20%

“…These heterocontacts can also overcome or reduce losses common to other c-Si cell architectures-for example, parasitic absorption or heavy impurity doping losses 7,13-15 -increasing the practical efficiency limit of this structure. Most efforts so far have focused on substituting one such heterocontact into an otherwise conventional c-Si cell, [16][17][18][19][20] demonstrating, in many cases, clear performance or fabrication advantages. The ultimate extension of this concept is to use a set of asymmetric heterocontacts in a single cell structure, sometimes referred to as the dopant-free asymmetric heterocontact or DASH cell.…”

“…The ultimate extension of this concept is to use a set of asymmetric heterocontacts in a single cell structure, sometimes referred to as the dopant-free asymmetric heterocontact or DASH cell. In our previous study, we presented a record 19.4% efficient DASH solar cell, 7 utilizing MoOx and LiFx based heterocontacts with thin amorphous silicon (a-Si:H) interfacial passivation layers. Although promising for a first proof-ofconcept, it is important to demonstrate that higher conversion efficiencies can be achieved, in line with the suggested higher efficiency potential of this architecture.…”

Multicrystalline Silicon Thin‐Film Solar Cells Based on Vanadium Oxide Heterojunction and Laser‐Doped Contacts

“…Finally, a contact consisting of 40 nm of titanium and 1 μm of aluminum was evaporated by electron beam and separated fingers were defined by photolithography. It should be mentioned that the metallization of the emitter region was different from the one reported in the previous study . In that work, a two‐level metallization with Ni/Al on the VO x and only Al on the base contacts was used.…”

“…This new technology avoids the usage of toxic and/or flammable dopant gas precursors with comparatively lower temperature processing. In particular, excellent results have been reported for IBC c‐Si solar cells fabricated using vanadium oxide (VO x ) as hole transport layer, whereas the n‐type base contacts are defined by laser processing of phosphorus‐doped amorphous silicon carbide (SiC x ( n )) stacks . In this work, we explore the viability of this technology when it is applied to LPC substrates with the objective of identifying the main advantages and issues of the structure.…”

Analysis of temperature dependent current-voltage and capacitance-voltage characteristics of an Au/V2O5/n-Si Schottky diode

“…16,17 In recent work,V 2 O 5 thin films have been used as hole conducting buffer layers for heterojunction solar cell and interdigited back contacted solar cells that achieved 15.7% and 19.7% conversion efficiency respectively. 18,19 However, room temperature current-voltage measurements are not sufficient to fully understand the current conduction phenomenon through the V 2 O 5 layer. Therefore, low temperature I-V and C-V measurements are necessary to get information on the charge transport mechanism through V 2 O 5 thin-film.…”