Spatial Atomic Layer Deposition of Aluminum Oxide as a Passivating Hole Contact for Silicon Solar Cells

Abstract

Herein, tunneling aluminum oxide (Al2O3) passivation layers are demonstrated to be a candidate for hole collecting, passivating contacts when coupled with a boron‐doped surface. These very thin Al2O3 films (1.5–3 nm) are deposited using spatial atomic layer deposition (ALD) on boron diffused (110–115 Ω □−1) hydrophilic surfaces operating as metal–insulator–semiconductor (MIS) contacts. The emitter saturation current density values of ≈57 fA cm−2 are achieved for the Al2O3 film thicknesses of 2 nm before metallization. At this same thickness, the contact resistivity values of 33 mΩ cm2 are obtained after metallization. Most importantly, the boron diffusion, wet chemical surface preparation, and spatial ALD of Al2O3 used to create these MIS structures are all performed with industrially relevant equipment on Cz wafers.

Ultrathin Aluminum Oxide Films Induced by Rapid Thermal Annealing for Effective Silicon Surface Passivation

“…[30] The results indicate that the RTAinduced Al 2 O 3 films can achieve remarkable passivation effect, even better than the commonly used ALD method. Although the measured lifetimes in all samples are lower as compared with those by ALD Al 2 O 3 films, [31,32] solar-grade silicon wafers with lower τ bulk are used in this work. The thermal ALD equipments are commonly used in photovoltaic industry and the ALD-Al 2 O 3 films can be a good reference here.…”

Process–Structure–Properties Relationships of Passivating, Electron‐Selective Contacts Formed by Atmospheric Pressure Chemical Vapor Deposition of Phosphorus‐Doped Polysilicon

“…[ 24 ] In this work, we present a passivating electron‐selective contact fabricated with APCVD in situ P‐doped poly‐Si layer on top of a thin SiO x layer grown using deionized water with dissolved ozone (DI–O 3 ). [ 4,25 ] Additionally, the influence of the deposition process and annealing process parameters on the microstructure, electrical properties, and passivation quality of the contact is reported, providing guidance on the optimal fabrication process for the APCVD‐based poly‐Si electron contacts. Finally, by the better understanding of the process–structure–properties relationship of the contact, we can achieve even lower saturation current density ( J 0 ) and junction resistivity compared to the previous work.…”

“…[1,2] The key to this contact technology is reducing recombination losses without increasing resistive losses. The passivating, carrier-selective functionality can be achieved using different materials systems, such as the stack of ultrathin dielectric layers including silicon oxide (SiO x ), [3] aluminum oxide (Al 2 O 3 ), [4][5][6] various transition metal oxides, [3,[5][6][7][8] and a stack of hydrogenated doped and undoped amorphous silicon (a-Si:H) layers. [9,10] Another effective approach is to use a very thin SiO x layer with a heavily doped polycrystalline silicon (poly-Si) layer, also known as a tunnel oxide passivated poly-Si contact (TOPCon) [11][12][13][14][15][16] or poly-Si on oxide (POLO).…”

Phosphorus-doped polysilicon passivating contacts deposited by atmospheric pressure chemical vapor deposition

“…Normally, the passivating functionality is provided by a very thin layer of dielectric or undoped semiconductor materials [5][6][7] including silicon oxide (SiO 2 or SiO x ), hydrogenated amorphous silicon (a-Si:H), and aluminum oxide (Al 2 O 3 ). The carrier-selective functionality can be provided by doping the absorber, as in a metal-insulator-semiconductor (MIS) cell [8][9][10][11][12], or a heterostructure with doped a-Si:H [13,14], transition metal oxides [15][16][17][18][19][20], transition metal nitrides [21,22], or doped polycrystalline silicon (poly-Si) [23][24][25][26][27][28].…”