两类异质结构中光生电荷分离效率与光电性质

Separation Efficiency of Photogenerated Charges and Photoelectric Properties in Two Types of Heterojunctions

首先制备Cu4Bi4S9纳米带与石墨烯不同比例复合体系(CBS-graphene),其中石墨烯质量分数分别为:0.4%,0.8%,1.2%,1.6%,2.0%和2.4%.以α-Fe_2O_3为电子受主,CBS和CBS-graphene为电子施主,制备成α-Fe_2O_3/CBS、α-Fe_2O_3/CBS-graphene两类异质结构及体相异质结太阳能电池.XRD检测结果表明,异质结两组分都达到了良好的结晶状态;而且,两类复合体系都呈现出了复合结构的光吸收特性,但光吸收性质无明显差异.对于CBS-graphene,随着石墨烯含量逐步增加其光伏性质逐渐增强,当石墨烯质量分数为1.6%时达到最佳光伏响应强度,此后其光伏性质逐渐减弱.稳态和电场诱导表面光电压谱表明两类异质结都具有优越的光伏性质,但α-Fe_2O_3/CBS-graphene呈现出明显优于α-Fe_2O_3/CBS的光伏响应.基于石墨烯质量分数为1.6%,α-Fe_2O_3/CBS和α-Fe_2O_3/CBS-graphene两类体相异质结太阳能电池最高光电转换效率分别为3.1%和6.8%.从异质结厚度、能级匹配、石墨烯导电网络以及优越的电子传输特性几个方面,详细讨论了光生电荷分离的影响因素及光生电荷传输动力学.

Firstly, different composites of Cu4 Bi4 S9 nanoribbons and graphene （CBS-graphene） were fabricated with gra- phene of 0.4, 0.8, 1.2, 1.6, 2.0 and 2.4 wt. %. Usingα-Fe2O3 as electron acceptor, CBS and CBS-graphene as electron do- nor, two types of heterojunctions （α-Fe2O3/CBS, α-Fe2O3/CBS-graphene） and bulk heterojunction （BHJ） solar cells were pre- pared. The XRD results show that α-Fe2O3 and CBS components can be indexed as the well-crystallized structures for two types of heterojunctions. Moreover, all of composite systems present the absorption characteristics of composite structure, but there is not an obvious difference from absorption spectra. For CBS-graphene, the surface photovoltage （SPV） increased gradually with graphene changing from 0.4 to 1.6 wt. %. Above 1.6 wt. M, the SPV signal decreased continuously. Besides, α-Fe2O3/ CBS-graphene exhibits the higher photovoltaic response than α-Fe2O3/CBS using steady state and electric field induced surface photovoltage spectroscopy. With graphene of 1.6 wt. %, α-Fe2O3/CBS and α-Fe2O3/CBS-graphene BHJ solar cells present the highest photoelectric conversion efficiencies of 3.1% and 6.8 %, respectively. From thickness of film, energy level matching, graphene conductive network and remarkably high electron mobility, etc. , the factors on the separation of photogenerated char- ges and the charge dynamics were analysed in detail.