Research on Crystalline Compound Semiconductors and Transparent-Conducting Oxides

晶体化合物半导体和透明导电氧化物的研究

• 批准号: RGPIN-2014-04152
• 负责人: Shih, Ishiang
• 金额: $ 1.82万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=587632
• 关键词: Research; Crystalline; Compound; Semiconductors; Transparent

Part A: Monocrystalline CuInSe2 -based Semiconductors for Solar Cells The first generation commercial solar cells in the market are predominantly manufactured using bulk polycrystalline Si or monocrystalline Si. Although the thermal stability of the current Si bulk solar cells is excellent, the energy pay back time is still long. The relatively long energy pay back time is mainly due to the indirect bandgap requiring a large substrate thickness of 200 µm or more for sufficient absorption and the high growth temperatures. The energy pay back time of the second generation thin film solar cells must be reduced for large scale terrestrial applications. The way to achieve the low energy pay back time is to adopt a semiconductor with a direct band gap and high optical absorption coefficients. There are two main material systems being developed for the second generation solar cell fabrication: CuInxGa1-xSe2 and CdTe. Using these semiconductors, the amount of material usage and energy consumption during the cell manufacturing can be reduced. In the applicant’s laboratory at McGill, research work has been performed on the Bridgman growth of monocystalline CuInSe2 (CIS) and CuInGaSe2 (CIGS). Both CIS and CIGS have very large optical absorption coefficients in the solar spectrum and a thin film with a thickness as small as 0.4 µm instead of 200 µm is capable of absorbing 98% of above bandgap photons in the solar spectrum. The performance of thin film cells containing trace of Na (due to inter diffusion from soda lime glass substrates) is much better than those without Na. Unfortunately, it is more difficult to study Na effects in CIS and CIGS thin films and the causes of performance improvement have not been conclusive. Therefore, research work will be performed in this project to study effects of Na on the microscopic and electronic properties of monocrystalline bulk CIS and CIGS. Research work will be performed to prepare ingots from melts containing different amounts of Na. In addition, research work will be made to prepare photovoltaic cells on the CIS and CIGS substrates containing Na. Special attention will be paid to the effect of Na on defect density for the CIGS surface and CIS-CIGS /CdS interface face. We plan to obtain Na results which can allow thin film solar cells to reach efficiencies more than 22%. Part B: Transparent and Conducting Oxides for Electronic Applications Transparent conductive oxides (TCO) are often microcrystalline thin films which have high transmission in the visible wavelength range and high conductivity. Known TCOs include F- or Sb-doped tin oxide, Sn- or Zn-doped indium oxide and Al-, B- or Ga-doped zinc oxide. The resistivity of the TCO films is limited to a value slightly above 10-4 ohm-cm due to a relatively low mobility (~10 cm2/V-sec) at high doping density of more than 1021 cm-3. The high doping concentration has caused a decrease in optical transmission at least in the long wavelength region. In order to improve the performance of devices involving the TCOs, it is desirable to develop thin films with high electron mobility so that the doping concentration can be reduced to obtain the same level of resistivity or to decrease further the resistivity. In the present project, modulation doping will be explored in the conductive oxides in order to increase the mobility to substantially greater than 100 cm2/V-sec while maintaining the high doping concentration. The improved TCOs will be deposited on the CIS and CIGS substrates developed in part A to form solar cells. We also plan to achieve thin film transistor devices with exceptional switching performance compared to the existing technology.

A部分： 太阳能电池用单晶CuInSe 2基半导体 市场上的第一代商业太阳能电池主要使用块状多晶硅或单晶Si制造。虽然目前的硅体太阳能电池的热稳定性很好，但能量回收时间仍然很长。相对较长的能量回收时间主要是由于间接带隙需要200 μm或更大的衬底厚度以获得足够的吸收和高生长温度。第二代薄膜太阳能电池的能量回收时间必须减少，以用于大规模的地面应用。实现低能量回收时间的方法是采用具有直接带隙和高光吸收系数的半导体。第二代太阳能电池主要有两种材料体系：CuInxGa 1-xSe 2和CdTe。使用这些半导体，可以减少电池制造过程中的材料使用量和能源消耗。 在申请人在麦吉尔的实验室中，对单晶CuInSe 2（CIS）和CuInGaSe 2（CIGS）的Bridgman生长进行了研究工作。CIS和CIGS在太阳光谱中都具有非常大的光学吸收系数，并且厚度小至0.4 μm而不是200 μm的薄膜能够吸收太阳光谱中98%的带隙以上光子。含有微量Na（由于钠钙玻璃基板的相互扩散）的薄膜电池的性能比不含Na的薄膜电池好得多。不幸的是，这是更困难的研究钠在CIS和CIGS薄膜的性能改善的原因还没有定论。因此，本计画将研究Na对单晶体CIS和CIGS的微观和电子性质的影响。将进行研究工作，以从含有不同量的Na的熔体制备锭。此外，还将研究在含Na的CIS和CIGS衬底上制备光伏电池。特别关注Na对CIGS表面和CIS-CIGS /CdS界面缺陷密度的影响。我们计划获得Na的结果，使薄膜太阳能电池的效率达到22%以上。 部分B： 电子用透明导电氧化物 透明导电氧化物（TCO）通常是在可见光波长范围内具有高透射率和高导电性的微晶薄膜。已知的TCO包括F-或Sb-掺杂的氧化锡、Sn-或Zn-掺杂的氧化铟和Al-、B-或Ga-掺杂的氧化锌。 由于在大于1021 cm-3的高掺杂密度下的相对低的迁移率（~10 cm 2/V-sec），TCO膜的电阻率被限制为略高于10-4 ohm-cm的值。 高掺杂浓度至少在长波长区域中引起光透射的降低。为了改善涉及TCO的器件的性能，期望开发具有高电子迁移率的薄膜，使得可以降低掺杂浓度以获得相同水平的电阻率或进一步降低电阻率。在本项目中，将在导电氧化物中探索调制掺杂，以便在保持高掺杂浓度的同时将迁移率增加到基本上大于100 cm 2/V-sec。改进的TCO将沉积在A部分开发的CIS和CIGS衬底上以形成太阳能电池。我们还计划实现与现有技术相比具有出色开关性能的薄膜晶体管器件。