Multiscale modeling of transport in silicon heterojunction solar cells

2017 ◽  
Vol 2017 (DPC) ◽  
pp. 1-15
Author(s):  
Pradyumna Muralidharan ◽  
Stephen M. Goodnick ◽  
Dragica Vasileska
Keyword(s):  
Monte Carlo ◽  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Device Performance ◽  
World Record ◽  
Single Junction ◽  
Heterojunction Solar Cells ◽  
Single Junction Solar Cell ◽  
Silicon Based

Silicon based single junction solar cell technology continued to make significant strides in the past year with new world record module efficiencies being reported for the Panasonic heterojunction with thin intrinsic layer (HIT) module (23.8%) and the SunPower rooftop silicon module (24.1%). The HIT cell which is comprised of amorphous silicon (a-Si) and crystalline silicon (c-Si) currently holds the world record efficiency (25.6%) for a silicon based single junction solar cell. Further improvement in this technology requires a rigorous understanding of the underlying physics of the device. The device performance of a-Si and c-Si heterojunction solar cells depends heavily on the nature of transport at the hetero interface and defect assisted transport through the a-Si. Different microscopic processes dominate transport in different regions of the device and take place across widely varying time scales. In this work we present a multiscale model which utilizes different simulation methodologies to study physics in various regions of the device, namely, the Ensemble Monte Carlo (EMC), Kinetic Monte Carlo (KMC), and Drift Diffusion (DD) solvers. The EMC studies the behavior of the photogenerated carriers at the heterointerface; the KMC analyzes transport of the photogenerated carriers through the intrinsic amorphous silicon (i-a-Si) barrier layer; and the DD solver calculates current and other device properties in the low field regions of the cell. These solvers are then self consistently coupled to analyze device performance. Previously, our KMC simulations have shown that hopping is the main mode of transport through the i-a-Si, and the photogenerated carries are collected by defect emission rather that Poole - Frenkel emission or direct tunneling1. In addition, using EMC simulations we have shown that the photogenerated carriers exhibit non Maxwellian behavior at the heterointerface2. This work specifically describes the self-consistent coupling of the DD and EMC solvers. By adding the EMC solver to the multiscale solver we are able to capture the high field behavior of the photogenerated carriers, and its affect on device parameters such as JSC, VOC, FF and efficiency.

A Multiscale Modeling Approach to Study Transport in Silicon Heterojunction Solar Cells

2016 ◽  
Vol 2016 (DPC) ◽  
pp. 002095-002110 ◽  
Author(s):  
Pradyumna Muralidharan ◽  
Stuart Bowden ◽  
Stephen M. Goodnick ◽  
Dragica Vasileska
Keyword(s):  
Monte Carlo ◽  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Buffer Layer ◽  
Kinetic Monte Carlo ◽  
Device Performance ◽  
Drift Diffusion ◽  
Heterojunction Solar Cells ◽  
Ensemble Monte Carlo

Single junction solar cells based on Silicon continue to be relevant and commercially successful in the market due to their high efficiencies and relatively low cost processing. Heterojunction solar cells based on crystalline (c-Si) and amorphous (a-Si) silicon (HIT Cells) have paved the way for devices with high VOC's (>700 mV) and high efficiencies (>20%) [1]. Panasonic currently holds the world record efficiency of 25.6% for its trademark a-Si/c-Si HIT cell [2]. The novel structure of the device precludes the usage of traditional methods (such as drift diffusion) to accurately understand the nature of transport. Theoretical models used by commercial simulators make a variety of assumptions that simplifies the transport problem (assumes a Maxwellian distribution of carriers) and thus lacks the sophistication to study defect transport. In this work we utilize a combination of Ensemble Monte Carlo (EMC) simulations, Kinetic Monte Carlo (KMC) simulations and traditional drift - diffusion (DD) simulations to study transport in the heterojunction solar cell. The device performance of an amorphous silicon (a-Si)/crystalline silicon (c-Si) solar cell depends strongly on the interfacial transport properties of the device [3]. The energy of the photogenerated carriers at the barrier strongly depends on the strength of the inversion at the heterointerface and their collection requires interaction with the defects present in the intrinsic amorphous silicon buffer layer [4]. In this work we present a multiscale model which can bridge the gap in time scales between different microscopic processes to study the transport through the interface by coupling an ensemble Monte Carlo (EMC) and a kinetic Monte Carlo (KMC). The EMC studies carrier properties such as the energy distribution function (EDF) at the heterointerface whereas the KMC method allows us to simulate the interaction of discrete carriers with discrete defects [5]. This method allows us to study defect transport which takes place on a time scale which is too long for traditional ensemble Monte Carlo's to analyze. We analyze the injection and extraction of carriers via defects by calculating transition rates for different processes. By using the principles of SRH recombination, this method can also be extended to study recombination processes at the interface and in the amorphous bulk which are crucial parameters for solar cell performance. Therefore, by using the multiscale approach all important processes can be studied rigorously to evaluate device performance. Our simulations indicate that a phonon assisted emission process from a defect is the most favored extraction mechanism and both Poole-Frenkel emission (<2%) and thermionic emission (<1%) were not significant. We extended our simulation methodology to study recombination at the interface and in the buffer layer of the device to find that the device performance is mainly interface recombination limited and that defect densities in the buffer layer have to be really high (>1018 cm-3) in order to degrade device performance.

scholarly journals N-I-P Micromorph Solar Cells on Aluminium Substrates

1996 ◽  
Vol 452 ◽  
Author(s):  
M. Goetz ◽  
P. Torres ◽  
P. Pernet ◽  
J. Meier ◽  
D. Fischer ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Spectral Response ◽  
Single Layer ◽  
Antireflection Coating ◽  
Microcrystalline Silicon ◽  
Single Junction ◽  
Junction Solar Cell ◽  
Single Junction Solar Cell

AbstractThe first successful deposition of ‘micromorph’ silicon tandem solar cells of the n-i-p-n-i-p configuration is reported. In order to implement the ‘micromorph’ solar cell concept, four key elements had to be prepared: First, the deposition of mid-gap, intrinsic microcrystalline silicon (μc-Si:H) by the 'gas purifier method', second, the amorphous silicon (a-Si:H) n-i-p single junction solar cell, third, the microcrystalline silicon n-i-p single junction solar cell and fourth, the ability of depositing on aluminium sheet substrates.All the solar cells presented have been deposited on flat aluminium sheets, using a single layer antireflection coating to couple the light into the cell. It is shown, that this antireflection concept- together with a flat substrate- holds for amorphous single junction solar cells, but it reaches its limit with the extended range of spectral response of the ‘micromorph’ cell.The best initial efficiencies for each category of n-i-p cells on flat substrates were: 8.7% for the amorphous silicon single junction cell, 4.9% for the microcrystalline silicon single junction cell and 9.25% for the ‘micromorph’ tandem cell.

scholarly journals Numerical Design of Ultrathin Hydrogenated Amorphous Silicon-Based Solar Cell

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
F. X. Abomo Abega ◽  
A. Teyou Ngoupo ◽  
J. M. B. Ndjaka
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Buffer Layer ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Theoretical Work ◽  
Silicon Based ◽  
The Impact ◽  
Hydrogenated Amorphous

Numerical modelling is used to confirm experimental and theoretical work. The aim of this work is to present how to simulate ultrathin hydrogenated amorphous silicon- (a-Si:H-) based solar cells with a ITO BRL in their architectures. The results obtained in this study come from SCAPS-1D software. In the first step, the comparison between the J-V characteristics of simulation and experiment of the ultrathin a-Si:H-based solar cell is in agreement. Secondly, to explore the impact of certain properties of the solar cell, investigations focus on the study of the influence of the intrinsic layer and the buffer layer/absorber interface on the electrical parameters ( J SC , V OC , FF, and η ). The increase of the intrinsic layer thickness improves performance, while the bulk defect density of the intrinsic layer and the surface defect density of the buffer layer/ i -(a-Si:H) interface, respectively, in the ranges [109 cm-3, 1015 cm-3] and [1010 cm-2, 5 × 10 13  cm-2], do not affect the performance of the ultrathin a-Si:H-based solar cell. Analysis also shows that with approximately 1 μm thickness of the intrinsic layer, the optimum conversion efficiency is 12.71% ( J SC = 18.95   mA · c m − 2 , V OC = 0.973   V , and FF = 68.95 % ). This work presents a contribution to improving the performance of a-Si-based solar cells.

Novel high-efficiency crystalline-silicon-based compound heterojunction solar cells: HCT (heterojunction with compound thin-layer)

2014 ◽  
Vol 16 (29) ◽  
pp. 15400-15410 ◽  
Author(s):  
Yiming Liu ◽  
Yun Sun ◽  
Wei Liu ◽  
Jianghong Yao
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Thin Layer ◽  
High Efficiency ◽  
Crystalline Silicon ◽  
Heterojunction Solar Cell ◽  
Heterojunction Solar Cells ◽  
Silicon Based

A novel high-efficiency c-Si heterojunction solar cell with using compound hetero-materials is proposed and denominated HCT (heterojunction with a compound thin-layer).

Improved metastability and performance of amorphous silicon solar cells

2014 ◽  
Vol 1666 ◽  
Author(s):  
Takuya Matsui ◽  
Adrien Bidiville ◽  
Hitoshi Sai ◽  
Takashi Suezaki ◽  
Mitsuhiro Matsumoto ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
High Efficiency ◽  
Chemical Vapor ◽  
Silicon Solar Cells ◽  
Cell Temperature ◽  
Single Junction Solar Cell ◽  
And Performance ◽  
Hydrogenated Amorphous

ABSTRACTWe show that high-efficiency and low-degradation hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells can be obtained by depositing absorber layers in a triode-type plasma-enhanced chemical vapor deposition (PECVD) process. Although the deposition rate is relatively low (0.01-0.03 nm/s) compared to the conventional diode-type PECVD process (∼0.2 nm/s), the light-induced degradation in conversion efficiency of single-junction solar cell is substantially reduced (Δη/ηini∼10%) due to the suppression of light-induced metastable defects in the a-Si:H absorber layer. So far, we have attained an independently-confirmed stabilized efficiency of 10.11% for a 220-nm-thick a-Si:H solar cell which was light soaked under 1 sun illumination for 1000 hours at cell temperature of 50°C. We further demonstrate that stabilized efficiencies as high as 10% can be maintained even when the solar cell is thickened to >300 nm.

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