Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

Abstract

The evolution of the contact scheme has driven the technology revolution of crystalline silicon (c-Si) solar cells. The state-of-the-art high-efficiency c-Si solar cells such as silicon heterojunction (SHJ) and tunnel oxide passivated contact (TOPCon) solar cells are featured with passivating contacts based on doped Si thin films, which induce parasitic optical absorption loss and require capitalintensive deposition processes involving flammable and toxic gasses. A promising solution to tackle this problem is to employ dopant-free passivating contact, involving the use of transparent and cost-effective wide band gap materials. In this review, we first introduce the dopant-free passivating contact, from carrier transport mechanisms, material classification to evaluation methods. Then we focus on the advances in different strategies to improve cell performance, including material property optimization, structural and interfacial engineering, as well as various post-treatments. At the end, the challenge and perspective of dopant-free passivating contact c-Si solar cells are discussed.

Rational Approach for High‐Efficiency Dopant‐Free Solar Cells Characterized with Key Parameters

“…Reproduced with permission. [ 111 ] Copyright 2022, Wiley‐VCH. c) Bandgap diagrams and work function positions (dashed lines) of different TCOs, CBMs, TMOs, and FCMs with the c‐Si energy band edges (gray bar) as a reference.…”

“…DFPC materials must be transparent to allow light to pass through and be absorbed by the c-Si. Therefore, transparent [111] Copyright 2022, Wiley-VCH. c) Bandgap diagrams and work function positions (dashed lines) of different TCOs, CBMs, TMOs, and FCMs with the c-Si energy band edges (gray bar) as a reference.…”

“…This is particularly critical in HIT solar cells, where the suppression of the growth of nanocrystalline Si is critical. Owing to the three dangling bonds, the energetic stability of new epitaxial Si atoms on the (111) plane is lower than those of the (100) and (011) planes. Hence, a-Si deposition on the (111) plane can inhibit nanocrystal growth, and thus the (111) pyramidal structures have practical applications in HIT cells.…”

“…Owing to the three dangling bonds, the energetic stability of new epitaxial Si atoms on the (111) plane is lower than those of the (100) and (011) planes. Hence, a-Si deposition on the (111) plane can inhibit nanocrystal growth, and thus the (111) pyramidal structures have practical applications in HIT cells. [27] However, reliance on pyramidal structures with specific surface orientations inherently limits the application of nanostructures such as nanocones and nanoholes.…”

Sub‐Stochiometric Nickel Oxide Hole‐Selective Contacts in Solar Cells: Comparison of Simulations and Experiments with Sputtered Films

“…[16,17] Concurrently, even though p-type oxides (Cu 2 O, NiO) were expected to work well as hole-selective contacts, their practical performance is often found insufficient as compared to competing n-type metal oxides due to their low hole conductivity and poor surface passivation. [18][19][20][21][22] Indeed, Pramod et al reported 3.9% efficiency in the device with sputtered Cu 2 O contacts. [18] Further, 5.48% efficiency was reached by Kurias et al using borondoped Cu 2 O contacts.…”