InGaAsP/InGaAs双结太阳电池的开路电压损耗抑制

Reducing Voc loss in InGaAsP/InGaAs dual-junction solar cells

现有1.0 eV/0.75 eV InGaAsP/InGaAs双结太阳电池的开路电压小于各子电池的开路电压之和,鲜有研究探索开路电压损耗的来源以及如何抑制。通过研究发现,InGaAs底电池背场/基区界面处的少数载流子输运的主要机制是热离子发射,而不是缺陷诱导复合。SIMS测试表明,采用InP或InAlAs背场均不能有效抑制Zn掺杂剂的扩散。此外,由于生长过程中持续的高温热处理,Ⅲ-Ⅴ族主元素在界面处发生了热扩散。为了抑制上述现象,提出了一种新型InP/InAlAs超晶格背场,并应用到InGaAs底电池中。制备得到的双结太阳电池在维持短路电流密度不变的情况下,开路电压提升到997.5 mV,与传统采用InP背场的双结太阳电池相比,开路电压损耗降低了30 mV。该研究成果对提升四结太阳电池的整体开路电压有重要意义。

Smaller Voc of 1. 0 eV/0. 75 eV InGaAsP/InGaAs double-junction solar cell(DJSC)than the Vocsum of individual subcells has been observed,and there is little information of the origin of such Vocloss and how to minimize it. In this paper,it is disclosed that the dominant mechanism of minority-carrier transport at back-surfacefield(BSF)/base interface of the bottom subcell is thermionic emission,instead of defect-induced recombination,which is in contrast to previous reports. It also shows that both InP and InAlAs cannot prevent the zinc diffusion effectively. In addition,intermixing of major Ⅲ-Ⅴ element occurs as a result of increasing thermal treatment. To suppress the above negative effects,an initial novel InP/InAlAs superlattice(SL)BSF layer is then proposed and employed in bottom InGaAs subcell. The Vocof fabricated cells reach 997. 5 mV,and a reduction of 30 mV in Voc loss without lost of Jsc,compared with the results of conventional InP BSF configuration,is achieved. It would benefit the overall Vocfor further four-junction solar cells.