Physical criteria for the interface passivation layer in hydrogenated amorphous/crystalline silicon heterojunction solar cell

Abstract

AFORS-HET (automat for simulation of heterostructures) simulation was utilized to explore the physical criteria for the passivation layer in hydrogenated amorphous/crystalline silicon heterojunction (SHJ) solar cells, by systematically investigating the solar cell current density–voltage (J–V) performance as a function of the interface defect density (Dit) at the passivation layer/c-Si hetero-interface, the thickness (t) of the passivation layer, the bandgap (Eg) of the passivation layer, and the density of dangling bond states (Ddb)/band tail states (Dbt) in the band gap of the passivation layer. The corresponding impact regulations were presented clearly. Except for Dit, the impacts of Ddb, Dbt and Eg are strongly dependent on the passivation layer thickness t. While t is smaller than 4–5 nm, the solar cell performance is less sensitive to the variation of Ddb, Dbt and Eg. Low Dit at the a-Si:H/c-Si interface and small thickness t are the critical criteria for the passivation layer in such a case. However, if t has to be relatively larger, the microstructure, i.e. the material quality, including Ddb, Dbt and Eg, of the passivation layer should be controlled carefully. The mechanisms involved were analyzed and some applicable methods to prepare the passivation layer were proposed.

Polarizable High‐Index Nanoparticles Used for Light‐Induced Crystal‐Silicon Passivation and Dielectric Antenna for High‐Efficiency Solar Cell

“…In contrast, the latter is a technique to alleviate the carrier density at the solid surface through an electric field induced by fixed charges. The dopants in the heterojunction contact structure are strictly limited to the outer a‐Si:H layers, requiring stringent passivation arising from the intrinsic a‐Si:H. [ 5,6 ] The induced surface potential in the c‐Si wafer therefore is fundamental in the heterojunction structure. [ 7,8 ]…”

“…In contrast, the latter is a technique to alleviate the carrier density at the solid surface through an electric field induced by fixed charges. The dopants in the heterojunction contact structure are strictly limited to the outer a-Si:H layers, requiring stringent passivation arising from the intrinsic a-Si:H. [5,6] The induced surface potential in the c-Si wafer therefore is fundamental in the heterojunction structure. [7,8] In heterojunction c-Si solar cells, deleterious interfacial defect densities can be effectively alleviated by the a-Si:H layer, leading to excellent interface passivation quality and rational band bending.…”

Polymer/Si Heterojunction Hybrid Solar Cells with Rubrene:DMSO Organic Semiconductor Film as an Electron-Selective Contact

“…The solar cell device can be simply divided into: absorption layer, hole-selective contact layer, and electron-selective contact layer. Taking an n-type crystalline silicon (c-Si) as the absorption layer of the solar cell for example, hole-selective contact, has been achieved by the addition of a boron dopant into Si bulk under high temperature (∼900 °C) for the traditional c-Si solar cells, or Si-based thin film (i.e., p-type hydrogenated amorphous silicon (a-Si:H­(p))) for the silicon heterojunction (SHJ) solar cells . Dopant-free asymmetric heterocontacts (DASH) solar cells use the material of molybdenum or tungsten oxide to achieve hole-selective contact. , Organic–inorganic hybrid solar cells use p-type polymer such as poly­(3,4-ethyl­ene­dioxy­thio­phene):­poly­(sty­rene­sulfonate) (PEDOT:PSS) or poly­(3-hexyl­thio­phene) (P3HT), , to promote the transparent of holes.…”

a-Si:H passivation layer growth by HWCVD for Si heterojunction solar cells: Critical dependence on substrate temperature

“…In this paper we explore the effect of substrate temperature (T sub ) for thin (i) a-Si:H passivation layer growth on the passivation quality of c-Si surfaces in terms of the minority carrier lifetime measurements. The likelihood that the passivation is not only an interface phenomenon but the 'a-Si:H layer' quality is as important as the a-Si:H/c-Si interface quality [8][9], further prompted us to investigate the electronic and micro-structural configuration of the corresponding bulk a-Si:H films (~600 nm) grown at different T sub in terms of crystallinity, defect density, Urbach energy and atomic hydrogen content in them. By making very thin a-Si:H passivation layers (<5 nm), the lifetime/passivation quality could be rendered to become less affected by the 'a-Si:H layer' properties [8], however, in that case the challenge would be to retain the same passivation quality at the interface.…”

“…The likelihood that the passivation is not only an interface phenomenon but the 'a-Si:H layer' quality is as important as the a-Si:H/c-Si interface quality [8][9], further prompted us to investigate the electronic and micro-structural configuration of the corresponding bulk a-Si:H films (~600 nm) grown at different T sub in terms of crystallinity, defect density, Urbach energy and atomic hydrogen content in them. By making very thin a-Si:H passivation layers (<5 nm), the lifetime/passivation quality could be rendered to become less affected by the 'a-Si:H layer' properties [8], however, in that case the challenge would be to retain the same passivation quality at the interface. This is because of the way a-Si:H films grows in the HWCVD techniques: initial island formation followed by coalescence between islands with increasing film thickness [10].…”