Donor and acceptor levels in impurity-doped semiconducting BaSi₂ thin films for solar-cell application

Abstract

Identification of donor and acceptor energy levels in BaSi 2 due to the suitable impurity injection of different types is very essential for the design and development of heterojunction or homojunction solar cells. In this article, donor and acceptor energy levels due to the impurity Sb-, In-, Ga-, Cu-, Al-, Ag-, P-, and B-doped BaSi 2 films grown by molecular beam epitaxy (MBE) were investigated. It was found that impurity Sb-, Ga-, Cu-, and P-doped BaSi 2 exhibited n-type conductivity, while impurity In-Al-, Ag-, and B-doped BaSi 2 exhibited p-type conductivity, using the Van der Pauw method at room temperature (RT). The temperature dependence of electron or hole concentrations indicated that the acceptor energy levels in impurity B-, In-, Ag-, and Al-doped BaSi 2 are 23, 86, 126, and 140 meV, respectively, and the donor energy levels in impurity Cu-, Sb-, P-, and Ga-doped BaSi 2 are 35, 47, 80, and 120 meV, respectively. The shallow acceptor level of 23 meV in p-type BaSi 2 due to B impurity atoms and two novel donor levels of 47 and 35 meV, respectively, due to Sb and Cu impurity atoms in n-type BaSi 2 were successfully identified for photovoltaic applications.

Investigation of thin-film p-BaSi2/n-CdS heterostructure towards semiconducting silicide based high efficiency solar cell

“…The p-type BaSi 2 can be realized through various group 3 One exceptional case has been found for Gallium (Ga) which is a group 3 dopant, but constitutes an n-type BaSi 2 instead of a p-type BaSi 2 [2]. Among them, Boron dopant can be introduced up to 10 20 cm −3 at RT [12] and it is the only acceptor impurity for obtaining high deposition rate due to low activation energy of Boron in BaSi 2 [2]. But the influence of intentionally employed impurities depends stalwartly upon the undoped BaSi 2 semiconductor's class.…”

“…It is a praiseworthy absorber material for TFSC due to its favourable optoelectronic properties such as high optical absorption coefficient (α) reaching 3 10 5 cm −1 [3][4][5], nearly optimum indirect energy band gap, E g of 1.3 eV [6][7][8][9][10], long minority carrier diffusion length of 10 μm [4,6,10,11], and lifetime of 14 μs [4,8]. Moreover, its absorption coefficient is 30 [12] to 40 [7] times larger than that of the single crystalline-Silicon (c-Si). For BaSi 2 solar cell, photon absorption begins at 1.3 eV and goes to maximum at 1.5 eV.…”

“…Electron thermal velocity, S n (cm s −1 ) Hole thermal velocity, S p (cm s −1 ) Electron mobility, m n (cm 2 V −1 s −1 ) 820[2,12] 100[29] 100[29] Hole mobility, m p (cm 2 V −1 s −1 ) 100 [2] 25 [29] 25 [29] Shallow uniform donor density, N D (cm −3 ) 0 1 10 17 a 1 10 18 a Shallow uniform acceptor density, N A (cm −3 ) Bulk defect density, N(t) total (cm −3 ) 1 10 14 a 1 10 14 a -Bulk defect density, N(t) peak (eV −1 cm −3 ) 1 10 16 a 1 10 16 a -N.B: a is a variable field.…”

Modelling and numerical analysis of ZnO/CuO/Cu2O heterojunction solar cell using SCAPS

“…Active or passive components in a broad range of commercial applications, such as active channel layers in solar cells as transparent conducting front electrodes and as electron or hole transport layers [6] or in the transistors that constitute active-matrix displays [7], were usually made by metal oxide materials. Besides some structures of photovoltaic cells [8][9][10], heterojunctions entirely based on metal oxides, so called all-oxide photovoltaic cells, have recently attracted considerable attention because of their promising potential to reduce photovoltaic prices due to their low cost, abundant, and inexpensive production methods [11][12][13].…”

Numerical simulation and optimization of Si/BaSi2 heterojunction and BaSi2 homojunction solar cells

“…For example, p-BaSi 2 can be achieved through B doping with hole concentration in a wide range from 10 16 to 10 19 cm −3 at room temperature [14,15]. n-BaSi 2 can be achieved through Sb, Ga or Cu doping with electron concentration from 10 15 to 10 20 cm −3 [16][17][18]. These all suggest the possibility to form BaSi 2 homojunction or BaSi 2 /Si heterojunction devices with controllable functional performance.…”