Modeling of transport in carrier‐selective contacts in silicon heterojunction solar cells

Abstract

High‐performance silicon heterojunction (SHJ) solar cells use carrier‐selective contact structures based on hydrogentated amorphous Si (a‐Si:H) to maximize collection of photogenerated carriers. The high open circuit voltages observed experimentally in SHJ cells require that the carrier‐selective contacts provide selectivity and passivation. However, a microscopic understanding of the dynamics of carrier transport through the a‐Si layer is currently lacking. In this paper, we explicitly simulate the transport of holes across the a‐Si:H(i) layer using a novel kinetic Monte Carlo approach. The hole‐selective contact structure investigated in this paper uses p‐type doped a‐Si:H(p) and intrinsic a‐Si:H(i) on an n‐type crystalline silicon wafer, where the selectivity is provided by the a‐Si:H(p) and the passivation is provided by the a‐Si:H(i). However, in addition to the passivation provided by the a‐Si:H(i), this layer also creates a potential barrier to the collection of photogenerated holes. There have been experimental studies in the literature that have suggested that multi‐phonon processes are the main transport mechanism that assists in the transport of holes across the intrinsic a‐Si:H barrier. Simulations presented here show that multi‐phonon injection of holes into the a‐Si:H(i) layer is the rate limiting step for transport across the a‐Si:H(i) layer. Our results indicate that multi‐phonon transport is strongly dependent on the electric field at the a‐Si:H(i)/c‐Si heterointerface as well. Transport simulations presented in this paper are consistent with experimental findings that multi‐phonon processes limit transport across the a‐Si:H(i) layer and are responsible for photocurrent suppression at the a‐Si:H(i)/c‐Si heterointerface when these processes are slower than the associated incident hole flux due to photo‐excitation.

Dipoles and defects caused by CO2 plasma improve carrier transport of silicon solar cells

“…To our surprise, these defect states on the other hand also show a positive role. Pradyumna Muralidharan et al 18,29 claimed that for a SHJ solar cell, charge transport through the i-a-Si:H layer depends on the defect/phonon assisted transport. Holes hop from defect to defect within the i-a-Si:H layer before they are collected.…”

“…Consequently, the dipole reduces the hole hopping distance and blocks electron transport. In addition, CO 2 PT also causes defect states that improve hole transition 18 but has a slightly negative impact on chemical passivation 19 . We optimized balance CO 2 PT duration for the i/p interface of SHJ solar cells, which boosts their fill factor ( FF ) from 77.61% to 82.37% and PCE from 22.16% to 23.59%.…”

UV Light-Induced Degradation of Industrial Silicon HJT Solar Cells: Degradation Mechanism and Recovery Strategies

“…These cells achieve high open-circuit voltages through the deposition of intrinsic hydrogenated amorphous silicon (ia-Si:H) on crystalline Si, providing excellent passivation to silicon surface states [3]. Carrier selective contacts are formed by depositing doped amorphous silicon (a(p/n)-Si:H) layers on both sides of the ai-Si:H film [4]. Transparent conductive oxide (TCO) films serve as conducting paths for carriers and are capped with metal contacts using screen printing [5].…”

Influence of Deposition Parameters of ITO Films on the Performance of HJT Solar Cells

“…In recent years, with the rapid iteration of solar cell technologies, HJT solar cells have attracted extensive attention due to their high conversion efficiency, high open circuit voltage, low temperature coefficient, low process temperature, and bifacial power generation. It is expected to become one of the mainstream high-efficiency solar cell technologies [1][2][3]. Its structure is shown in Figure 1.…”