石墨烯纳米墙/硅纳米线阵列太阳能电池的制备及其性能
张 铃1,2,3,黄菲菲1,2,3,程其进1,2,3*

(1.厦门大学能源学院,福建 厦门 361102; 2.厦门大学深圳研究院,广东 深圳 518000; 3.厦门大学电子科学与技术学院,福建 厦门 361102)

等离子体增强化学气相沉积法; 石墨烯纳米墙; 硅纳米线阵列; 肖特基结; 太阳能电池

Fabrication and performance of graphene nanowalls/silicon nanowire array solar cells
ZHANG Ling1,2,3,HUANG Feifei1,2,3,CHENG Qijin1,2,3*

(1.College of Energy,Xiamen University,Xiamen 361102,China; 2.Shenzhen Research Institution of Xiamen University,Shenzhen 518000,China; 3.School of Electronic Science and Engineering,Xiamen University,Xiamen 361102,China)

plasma enhanced chemical vapor deposition method; graphene nanowall; silicon nanowire array; Schottky junction; solar cell

DOI: 10.6043/j.issn.0438-0479.202004038

备注

硅纳米线阵列(SiNWA)因其优异的陷光性在石墨烯/硅异质结太阳能电池研究中引起了广泛关注.然而平面结构的石墨烯难以与SiNWA形成包覆结构,严重影响了器件的光伏性能.该文采用等离子体增强化学气相沉积法直接在SiNWA上生长石墨烯纳米墙(GNWs),与SiNWA形成核壳结构,增加了器件的有效结区面积并抑制了硅纳米线表面的载流子复合; 研究了生长时间对GNWs的晶体质量、光学和电学性能、形貌的影响.结果表明:所制备的GNWs可形成良好的导电网络并表现出p型掺杂; 随着生长时间的延长,GNWs的透光性下降,导电性增强,对SiNWA的包覆性变好; 当GNWs生长时间为120 s时,制备的GNWs/SiNWA太阳能电池获得了4.11%的最佳光电转换效率.该研究为制备低成本、高效率的石墨烯/硅太阳能电池提供了一条工艺简单而有效的途径.

Objective s:Micro/nano structures of silicon wafers such as silicon nanowire array (SiNWA) have been widely used in graphene/silicon Schottky heterojunction solar cells due to their excellent light trapping properties. However, two-dimensional planar graphene (Gr) has been substantiated to be difficult to form a perfect coating structure with three-dimensional SiNWA, whichseriously affects the photovoltaic performance of the fabricated solar cells. Based on the assumption that graphene nanowalls (GNWs) can fit perfectly with SiNWA and thereby greatly increase the effective junction area, this study attempted to replacetwo-dimensional planar graphene with three-dimensionalGNWs and to construct GNWs/SiNWA solar cells. Methods :A plasma enhanced chemical vapor deposition (PECVD) methodwas employed to directly grow GNWs on SiNWA. The effect of growth time on the crystalline quality, optical and electrical properties, as well as surface morphology of the synthesized GNWs was studied.Furthermore, the graphene/Si solar cells werefabricated by growing GNWs of different growth timesdirectly on SiNWA. The photovoltaic performance of the as-fabricated solar cells ofthe GNWs preparedwith different growth times was carefully investigated.It is worth mentioning that the direct growth method of GNWs is simpler for the device fabrication than the traditional transfer method of GNWs. Results :Firstly, for the Raman spectra of the GNWs prepared with PECVD method, as the growth time increased from 60 s to 150s,the position of the G peakhad a red shift and the intensity ratio of the 2D peak and the G peakincreased from 0.25 to 0.63, indicating that the as-prepared GNWs exhibitedalevelofp-typedopingand hadfewer defects at a higher growth time. It wasshown thatwhenthe growth time increased from 60s to 150s, the thickness of GNWs grown on planar siliconincreased from 65 nm to 166 nm, which resulted in a decreasein the transmittance and the sheet resistance of GNWs. For the GNWs grown on SiNWA,as the growth time increased from 60 s to 150 s, GNWs grew along SiNWAfrom the top to bottom, and gradually formed a core-shell structure with SiNWA. The formation of the core-shell structure of GNWs/SiNWA suggests that an effective heterojunction of GNWs and SiNWAwasformed. It wasfound that the longer the growth time of GNWs, the larger the effective junction area of the GNWs/SiNWAheterojunction. Meanwhile, according to the SEM images, the GNWs grown on SiNWAwereinterconnected, thus forming anoutstandingconductive network. Furthermore, the GNWs/SiNWA solar cells were successfully fabricatedusingGNWs deposited with different growth times.With the increase in the growth time from 60 s to 150 s,the increased effective GNWs/SiNWA heterojunction area and conductivity as well asthe decreased transmittanceof GNWsachieved atrade-off. An optimal photovoltaic conversion efficiency (PCE) of 4.11% waseventually achieved for the fabricated GNWs/SiNWA solar cells when the growth time of GNWs was 120 s,which is the pristine PCEof the solar cell without any chemical or noble metal doping as well asinterlayer treatment. Conclusion s:In conclusion, GNWs were directly deposited on SiNWA withPECVD method, and then novel GNWs/SiNWA Schottky junction solar cells were fabricated. The direct growth method of GNWs wasnot only easy to fabricate solar cells, but also avoidedany damage and defects caused by the traditional transfer method of GNWs. In order to obtain GNWs/SiNWA solar cells with the best photovoltaic performance, the growth time of GNWs was optimized, and the effect of the growth time on the crystal quality, optical and electrical properties, and surface morphology of GNWs wasalso investigated. The results showed that the as-prepared GNWs couldform a good conductive network on the surface of SiNWA and exhibited p-type doping. The growth time directly affected the light transmittance, electrical conductivity and coverage of GNWs on SiNWA. Finally, the as-prepared GNWs/SiNWA solar cell achieved the maximum PCE of 4.11% when the growth time was 120 s. This study provides a simple and efficient solution for fabricating low-cost, high-efficiency graphene/Si solar cells.