Novel field‐effect passivation for nanostructured Si solar cells using interfacial sulfur incorporation

Abstract

Surface passivation of a nanostructured Si solar cells plays a crucial role in collecting photogenerated carriers by mitigating carrier recombination at surface defect sites. Interface modification by additional sulfur (S) incorporation is proposed to enhance the field‐effect passivation performance. Here, we report that simple annealing in a H2S ambient induced additional negative fixed charges at the interface between atomic‐layer‐deposited Al2O3 and nanostructured Si. Annealing at various temperatures allowed us to control the S concentration and the fixed charge density. The optimized S incorporation at the interface significantly enhanced the negative fixed charge density and the minority carrier lifetime up to ~5.9 × 1012 cm−2 and ~780 μs, respectively. As a result, the internal quantum efficiency was nearly two times higher in the blue response region than that of control cells without S incorporation. Copyright © 2017 John Wiley & Sons, Ltd.

Black Si Photocathode with a Conformal and Amorphous MoSx Catalytic Layer Grown Using Atomic Layer Deposition for Photoelectrochemical Hydrogen Evolution

“…The ALD a-MoS x electrocatalyst layer was also employed for nanostructured Si photocathodes (black Si), which have an average light absorbance of ∼95% in the broad wavelength region of incident light (see Figure S5). Black Si was fabricated by the metal-assisted chemical etching (MaCE) method, − and a 1 nm-thick SiO 2 surface passivation layer was grown using rapid thermal oxidation. The schematic structure of the black Si photocathode is illustrated in Figure a.…”

Sulfur-Enhanced Field-Effect Passivation using (NH4)2S Surface Treatment for Black Si Solar Cells

“…In general, negative fixed charges at the interface between Al 2 O 3 and Si are induced by tetrahedrally coordinated Al in Al 2 O 3 near the Si interface. , Here, the S absorbed on the Si surface by (NH 4 ) 2 S solution treatment replaced O in the Al 2 O 3 near the interface. This increased the number of tetrahedrally coordinated Al in Al 2 O 3 , because the larger radius of S compared to O induced a close-packed array with Al atoms that occupy two-thirds of the tetrahedrally coordinated sites when bonded with Al atoms. This leads to an increase in − Q f ; this is called “S-enhanced field-effect passivation”. − …”

“…This is because NH 4 OH was generated from the reaction of (NH 4 ) 2 S with H 2 O [(NH 4 ) 2 S + 2H 2 O => 2NH 4 OH + H 2 S] and etched the Si surface . As a result, the high-index Si planes such as (110) and (111) were exposed, increasing the number of positive fixed charges at the interface and thus decreasing − Q f . , Therefore, the optimized (NH 4 ) 2 S solution treatment time for a flat Si substrate in terms of − Q f was 20 min. This optimization depends on the concentration of (NH 4 ) 2 S in the solution.…”

Interfaces in Atomic Layer Deposited Films: Opportunities and Challenges

“…This allows for the formation of chemically stable -S-terminated surfaces with minimal defects. [24][25][26][27][28][29][30][31][32] However, other III-V surfaces are not easily passivated where (NH 4 ) 2 S treatment leads to the formation of surface oxides. [33] In addition, other interfacial passivation layers, such as germanium, [34] silicon, and Si/Si 3 N 4 , [35] tend to exhibit superior interfacial properties on GaAs and InGaAs.…”