Insights into post-growth doping and proposals for CdTe:In photovoltaic devices

Research data on investigations into n-type CdTe thin film solar cells. Abstract. This paper is motivated by the potential advantages of higher doping and lower contact barriers in CdTe photovoltaic devices that may be realized by using n- type rather than the conventional p-type solar absorber layers. We present post-growth doping trials for indium in thin polycrystalline CdTe films using diffusion of indium metal and with indium chloride. Chemical concentrations of indium up to 1019 cm-3 were achieved and the films were verified as n-type by hard x-ray photoemission. Post growth chlorine treatment (or InCl3) was found to compensate the n-doping. Trial structures comprising CdS/CdTe:In verified that the doped absorber structures performed as expected both before and after chloride treatment, but it is recognized that this is not an optimum combination. Hence in order to identify how the advantages of n-type absorbers might be fully realized in future work, we also report simulations of a range of p-n junction combinations with n-CdTe, a number of which have the potential for high Voc.

n型碲化镉（CdTe）薄膜太阳能电池研究相关科研数据
摘要。本研究的初衷在于：相较于传统p型太阳能吸收层，采用n型吸收层可使碲化镉光伏器件获得更高掺杂浓度与更低接触势垒的潜在优势。本研究针对多晶碲化镉薄膜开展后期铟掺杂试验，分别采用金属铟扩散法与氯化铟法进行掺杂。最终实现了铟化学浓度最高达10¹⁹ cm⁻³的掺杂效果，并通过硬X射线光电子能谱（hard x-ray photoemission）验证了薄膜的n型导电属性。研究表明，后期氯化处理（或氯化铟处理）会对n型掺杂产生补偿作用。由硫化镉（CdS）/掺铟碲化镉（CdTe:In）构成的试验器件结构证实，掺杂后的吸收层结构在氯化处理前后均符合预期性能表现，但该组合并非最优方案已得到学界认可。因此，为明确未来研究中如何充分发挥n型吸收层的优势，本研究还针对多款搭配n型碲化镉的p-n结组合开展了模拟分析，其中部分组合具备实现高开路电压（Voc）的潜力。