Study of thin film poly-crystalline CdTe solar cells presenting high acceptor concentrations achieved by in-situ arsenic doping
Study of thin film poly-crystalline CdTe solar cells presenting high acceptor concentrations achieved by in-situ arsenic doping
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DOI：
10.1016/j.solmat.2019.02.025
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发表时间：
2019-06-01
影响因子：
6.9
通讯作者：
Irvine, S. J. C.
中科院分区：
文献类型：
--
作者：
Kartopu, G.;Oklobia, O.;Irvine, S. J. C.
使用V族元素（As、P和Sb）对CdTe进行掺杂在追求增加CdTe薄膜太阳能器件的电池电压方面已经引起了兴趣。对大块CdTe晶体的研究表明，通过高工艺温度和/或Cd过压下的快速热淬火，用As、P或Sb可以实现比传统铜处理高得多的受主浓度。我们报道了一个全面的研究原位砷掺杂的多晶CdTe太阳能电池的MOCVD，其中高受体密度，接近3 × 10（16）cm（-3），在390 ℃的低生长温度下实现。在晶界处没有发现As偏聚，即使10（19）As cm（-3）。由于As-Te替代掺杂和深能级缺陷，在升高的As浓度下观察到浅受主能级（+ 0.1 eV）。对具有可变As掺杂的器件进行了分析。在高浓度下观察到耗尽层变窄，体复合增强，以及器件电流和红色响应降低，尽管由于光学带隙减小而导致小的近红外增益。器件建模表明，当吸收剂掺杂相对较高时，n型窗口层的性质和相关的界面复合速度是非常关键的，这表明了获得高电池电压的途径。
Doping of CdTe using Group-V elements (As, P, and Sb) has gained interest in pursuit of increasing the cell voltage of CdTe thin film solar devices. Studies on bulk CdTe crystals have shown that much higher acceptor concentration than the traditional copper treatment is possible with As, P or Sb, enabled by high process temperature and/or rapid thermal quenching under Cd overpressure. We report a comprehensive study on in-situ As doping of poly-crystalline CdTe solar cells by MOCVD, whereby high acceptor densities, approaching 3 x 10(16) cm(-3) were achieved at low growth temperature of 390 degrees C. No As segregation could be detected at grain boundaries, even for 10(19) As cm(-3). A shallow acceptor level (+ 0.1 eV) due to As-Te substitutional doping and deep-level defects were observed at elevated As concentrations. Devices with variable As doping were analysed. Narrowing of the depletion layer, enhancement of bulk recombination, and reduction in device current and red response, albeit a small near infrared gain due to optical gap reduction, were observed at high concentrations. Device modelling indicated that the properties of the n-type window layer and associated interfacial recombination velocity are highly critical when the absorber doping is relatively high, demonstrating a route for obtaining high cell voltage.