Rupendra Kumar Sharma , Abhinav Deep Pakki , Jakub Holovský
{"title":"Silicon heterojunction solar cells: Excellent candidate for low light illuminations","authors":"Rupendra Kumar Sharma , Abhinav Deep Pakki , Jakub Holovský","doi":"10.1016/j.solmat.2024.113001","DOIUrl":null,"url":null,"abstract":"<div><p>The current solar cells and modules are marketed according to the behaviour at standard test conditions (STC), however, these devices are more often operated at lower irradiance levels. The dependence on illumination stems mainly from the voltage at the open circuit and at the maximum power point. The latter might also be strongly influenced by serial resistance, but that is more an engineering problem not addressed here. More fundamentally, the voltage is determined by quasi-Fermi levels at the contacts. In the case of unconstrained conductivity between the absorber and electrode, the quasi-Fermi levels are flat, and determined by their splitting in the absorber. Our analysis shows that the modulation doping mechanism working in Si heterojunction solar cell between the doped amorphous Si layer with a higher bandgap and crystalline absorber with a lower bandgap can, for certain parameter settings, lead to strongly depleted contact layer that limits conduction. This is a prerequisite for decoupling the quasi-Fermi level between contact and absorber and offers the possibility for additional voltage increase. Based on this understanding, we simulate a heterojunction solar cell with a varying thickness and doping of amorphous silicon p-type contact. We demonstrate that for a certain combination of thinner or lower-doped contact, higher efficiency at low illumination can be achieved compared to the technological baseline. This is fully in line with the experimental findings. This analysis is crucial not only for using solar cells for indoor applications but also for designing photovoltaic modules optimized for low irradiance, potentially increasing the level of self-sufficiency of buildings.</p></div>","PeriodicalId":429,"journal":{"name":"Solar Energy Materials and Solar Cells","volume":null,"pages":null},"PeriodicalIF":6.3000,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Solar Energy Materials and Solar Cells","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0927024824003131","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
The current solar cells and modules are marketed according to the behaviour at standard test conditions (STC), however, these devices are more often operated at lower irradiance levels. The dependence on illumination stems mainly from the voltage at the open circuit and at the maximum power point. The latter might also be strongly influenced by serial resistance, but that is more an engineering problem not addressed here. More fundamentally, the voltage is determined by quasi-Fermi levels at the contacts. In the case of unconstrained conductivity between the absorber and electrode, the quasi-Fermi levels are flat, and determined by their splitting in the absorber. Our analysis shows that the modulation doping mechanism working in Si heterojunction solar cell between the doped amorphous Si layer with a higher bandgap and crystalline absorber with a lower bandgap can, for certain parameter settings, lead to strongly depleted contact layer that limits conduction. This is a prerequisite for decoupling the quasi-Fermi level between contact and absorber and offers the possibility for additional voltage increase. Based on this understanding, we simulate a heterojunction solar cell with a varying thickness and doping of amorphous silicon p-type contact. We demonstrate that for a certain combination of thinner or lower-doped contact, higher efficiency at low illumination can be achieved compared to the technological baseline. This is fully in line with the experimental findings. This analysis is crucial not only for using solar cells for indoor applications but also for designing photovoltaic modules optimized for low irradiance, potentially increasing the level of self-sufficiency of buildings.
目前,市场上销售的太阳能电池和模块都是根据标准测试条件(STC)下的性能来销售的,但这些设备通常在较低的辐照度水平下运行。对光照度的依赖主要源于开路电压和最大功率点电压。后者也可能受到串行电阻的强烈影响,但这更多是一个工程问题,在此不做讨论。从根本上说,电压是由触点上的准费米级决定的。在吸收器和电极之间的导电性不受限制的情况下,准费米级是平坦的,并由其在吸收器中的分裂决定。我们的分析表明,在硅异质结太阳能电池中,带隙较高的掺杂非晶态硅层和带隙较低的晶体吸收层之间的调制掺杂机制在某些参数设置下会导致接触层的强耗尽,从而限制传导。这是触点和吸收体之间准费米级解耦的先决条件,并提供了额外提高电压的可能性。基于这一认识,我们模拟了一个具有不同厚度和掺杂的非晶硅 p 型触点的异质结太阳能电池。我们证明,与技术基线相比,对于较薄或较低掺杂的触点的特定组合,可以在低照度下实现更高的效率。这与实验结果完全一致。这一分析不仅对太阳能电池的室内应用至关重要,而且对设计针对低辐照度进行优化的光伏模块也至关重要,有可能提高建筑物的自给自足水平。
期刊介绍:
Solar Energy Materials & Solar Cells is intended as a vehicle for the dissemination of research results on materials science and technology related to photovoltaic, photothermal and photoelectrochemical solar energy conversion. Materials science is taken in the broadest possible sense and encompasses physics, chemistry, optics, materials fabrication and analysis for all types of materials.