Cu_2O/ZnO氧化物异质结太阳电池的研究进展

介绍了近年来低成本Cu_2O/ZnO氧化物异质结太阳电池方面的研究进展.应用于光伏器件的吸收层材料Cu_2O是直接带隙半导体材料,天然呈现p型;其原材料丰富,且对环境友好.Cu_2O/ZnO异质结太阳电池结构主要有平面结构和纳米线/纳米棒结构.纳米结构的Cu_2O太阳电池提高了器件的电荷收集作用;通过热氧化Cu片技术获得的具有大晶粒尺寸平面结构Cu_2O吸收层在Cu_2O/ZnO太阳电池应用中展现出了高质量特性.界面缓冲层(如i-ZnO,a-ZTO,Ga_2O_3等)和背表面电场(如p~+-Cu_2O层等)可有效地提高界面处能级匹配和增强载流子输运.10 nm厚度的Ga_2O_3提供了近理想的导带失配,减少了界面复合;Ga_2O_3非常适合作为界面层,其能够有效地提高Cu_2O基太阳电池的开路电压V_(oc)(可达到1.2 V)和光电转换效率.p~+-Cu_2O(如Cu_2O:N和Cu_2O:Na)能够减少器件中背接触电阻和形成电子反射的背表面电场(抑制电子在界面处复合).利用p型Na掺杂Cu_2O(Cu_2O:Na)作为吸收层和Zn_(1-x)Ge_x-O作为n型缓冲层,Cu_2O异质结太阳电池(器件结构:MgF_2/ZnO:Al/Zn_(0.38)Ge_(0.62)-O/Cu_2O:Na)光电转换效率达8.1%.氧化物异质结太阳电池在光伏领域展现出极大的发展潜力.

Progress of Cu2O/ZnO oxide heterojunction solar cells

Recent progress of low cost Cu₂O/ZnO hetero-junction solar cells is reviewed in this paper. The Cu₂O used as an absorbing layer in photovoltaic cells is a direct bandgap semiconductor, exhibiting natural p-type conductivity. The source material of Cu₂O-based solar cells is abundant and environmentally friendly. The main device structure of Cu₂O/ZnO solar cells presents a planar and nano-wire/nano-rod configuration. The nanostructured Cu₂O architecture conduces to charge collection in the device. The planar Cu₂O absorbing layer with large grain size, achieved through the thermal oxidation of Cu sheets, exhibits high quality of the Cu₂O/ZnO solar cells. The interface buffer layer (like i-ZnO, a-ZTO and Ga₂O₃) and back surface field (BSF, such as p⁺-Cu₂O) can effectively improve energy band alignment match and increase carrier transport. The Cu₂O paired with a 10-nm-thick Ga₂O₃ layer provides a nearly ideal conduction band offset and thus reduces the interface recombination. The Ga₂O₃ is a highly suitable buffer layer for enhancing the V_oc (V_oc value reaches 1.2 V) and conversion efficiency of Cu₂O-based solar cells. The p⁺-Cu₂O like N-doped Cu₂O (Cu₂O:N) and Na-doped Cu₂O (Cu₂O:Na) can reduce back-contact resistance and create an electron-reflecting back surface field in the Cu₂O based solar cells. When a p-type Cu₂O: Na acts as an absorbing layer and a zinc-germanium-oxide (Zn_1-xGe_x-O) thin film is used as an n-type layer (buffer), Cu₂O hetero-junction solar cell with the device structure MgF₂/Al-doped ZnO (ZnO:Al)/Zn_0.38Ge_0.62-O/Cu₂O:Na shows an efficiency of 8.1%. The oxide hetero-junction solar cells have a great potential application in the future photovoltaic field.