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钙钛矿太阳电池优化及钙钛矿/硅叠层电池制备

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/10/31 9:25:16  

摘要:近年来,有机-无机杂化钙钛矿太阳电池由于制备工艺简单、制作成本低、转换效率高等优势,在光伏领域掀起了研究的热潮。但由于发展时间尚短,要实现更大的跨越和应用,还需要对电池进行进一步的研究和优化。另外,目前占领最大光伏市场的晶硅太阳电池效率接近其理论最高效率,制备钙钛矿/硅叠层电池是突破效率限制的最有效途径。本文首先从界面修饰、溶剂工程、电子传输层优化等方面入手,对钙钛矿太阳电池性能进行优化。并在此基础上,构建了机械堆叠四端式和单片集成两端式钙钛矿/晶硅串联电池,通过增强晶硅底电池的长波响应,提高串联电池的光电转换效率。具体研究内容如下:

(1) 利用石墨烯量子点对钙钛矿晶界进行钝化。石墨烯量子点掺入量为7 vol.%时,能够获得最高的转换效率(17.62%),比纯钙钛矿太阳电池效率提高了8.2 %。通过一系列测试手段及密度泛函理论计算,对器件性能改善背后的作用机制进行分析。结果发现石墨烯主要有两个作用,钝化钙钛矿晶界处的电子陷阱,并加速电子的抽取和转移。

(2) 通过溶剂工程实现室温不退火条件下制备高质量的钙钛矿薄膜。系统研究溶剂体系对钙钛矿形貌、结晶性及光伏性能影响。DMAc/NMP作为混合溶剂时,钙钛矿电池具有最高的转换效率17.38%,比使用DMSO基混合溶剂时提高了近10%。更重要的是,即使钙钛矿薄膜不经过任何退火过程,DMAc/NMP溶剂获得的钙钛矿电池也能获得17.09%的效率,而基于DMAc/DMSO溶剂的器件效率仅为3.81%。对钙钛矿材料结晶的中间过程的表征结果显示NMP基溶剂能够使得钙钛矿在滴加反溶剂时室温下瞬间结晶,从而不需要进一步的退火处理。

(3) 采用ALD沉积TiO2薄膜实现电子传输层的低温制备,同时ALD法制备更高效的SnO2电子传输层代替传统的TiO2,提高平面结构钙钛矿电池的工作性能。本节首先研究TiO2生长温度和厚度对薄膜光电性能的影响,结果显示200 ℃下沉积15nm厚的TiO2薄膜时,电池效率最高,为13.72%,但和溶胶凝胶法制备的TiO2相比,电池性能降低幅度较大。用ALD沉积SnO2代替TiO2后,不仅电池效率提高到了17.46%,而且迟滞现象大大改善,这是因为ALD沉积的SnO2与钙钛矿能级匹配,能够快速抽取电子,降低钙钛矿/SnO2界面处的载流子复合。

(4) AlOx和 SiNx背钝化的PERC太阳电池被用作底电池,和钙钛矿电池构建钙钛矿/硅四端叠层电池。为了最大化的利用顶电池透过的光,对PERC电池的反射中心波长进行调节,降低反射,提高长波范围的光谱响应。随着中心波长的增大,PERC电池在近红外区域的EQE变大,从而获得更高的短路电流密度和光电转换效率。最终钙钛矿/PERC四端串联电池获得了21.4 %的转换效率。

(5) 以30μm厚的超薄硅片为基底制备IBC电池,并构建4-T钙钛矿/超薄IBC串联电池。利用SiNWs陷光结构来降低硅片对太阳光谱的反射,并用ALD沉积Al2O3来钝化SiNWs。15 nm厚的Al2O3即可获得良好的钝化效果,有效提高SiNWs的少子寿命。最终超薄IBC电池获得了16.61 %的效率,而钙钛矿/超薄IBC串联电池获得了21.85 %的效率。

(6) 以SHJ电池为基底,制备2-T钙钛矿/硅叠层电池,从两个方面对电池进行优化。首先通过改变钙钛矿材料中Br的含量,对钙钛矿材料的带隙进行调节,通过光电性能的表征,确定最佳Br含量。当x=0.2时,FA0.83Cs0.17Pb(I0.8Br0.2)3基钙钛矿电池具有最高的转换效率,为16.77 %。另外,对SHJ电池正表面进行SiNWs织构化处理,以期获得良好的陷光效果。最终制得了效率为19.01 %的2-T钙钛矿/SHJ叠层电池。

Recently, organic-inorganic hybridperovskite solar cells have drawn tremendous attention due to their easyproduction, low cost and rapidly improving photoelectric conversion efficiency.Further research and optimization are still needed to achieve the greater leapand wider application for the short period of development. Besides, the highestefficiency of silicon solar cells, which dominate most of the photovoltaicmarket, has been very close to their theoretical efficiency. The fabrication ofperovskite/silicon tandem solar cells is one of the most effective way to breakthe efficiency limitation. In this study, the performance of perovskite solarcells is firstly enhanced through the interface modification, solventengineering and electron transport layer optimization. Then, the mechanicallystacked 4-T and monolithic integrated 2-T peroskiter/silicon tandem devices areformed, and the performances are enhanced through increasing the spectralresponse of the silicon bottom solar cells. The main research contents are asfollows:

(1) Graphene quantum dots (GQDs) are usedto passivate the grain boundaries of CH3NH3PbI3. The highest efficiency(17.62%) is achieved via decoration with 7% GQDs, which is an 8.2% enhancementwith respect to a pure perovskite based device. Various measurements and thedensity-functional theory calculationsare employed to analyse the mechanismbehind the improvement in device performance. The findings reveal two importantroles played by GQDs, that GQDs can effectively passivate the electron traps atthe perovskite grain boundaries and are conducive to facilitating electronextraction and transportation.

(2) The solvent engineering is utilized torealize the fabrication of high-quality perovskite thin films at room temperaturewithout the need for annealing. The effects of different solvents, includingDMF/DMSO, DMAc/DMSO, DMF/NMP and DMAc/NMP co-solvents, on the morphology,crystallinity and photovoltaic properties of perovskite films are investigatedsystematically. PSCs fabricated from DMAc/NMP co-solvents show the best PCE of17.38%, which is about 10% improvement compared to that of the device based onDMF/DMSO or DMAc/DMSO co-solvents. Notably, 17.09% efficiency has been achievedeven without any post-annealing process for the device based on DMAc/NMPco-solvents. However, only 3.81% efficiency can be obtained for the devicebased on DMAc/DMSO co-solvents under the same conditions. The observedphenomenon is mainly due to the fact that the NMP-included solvents can inducean instant crystallization once the anti-solvent drips on the films at roomtemperature.

(3) ALD method is employed to deposit TiO2thin film, which realizes the low temperature preparation of electron transportlayer (ETL). Besides, SnO2 compact layer is also deposited through ALD toinstead of the traditional TiO2 layer, which leads to an enhanced performanceof the planar PSC. The effects of deposition temperature and thicknesses of theTiO2 thin films on the optical and electrical properties have been investigated.And the highest efficiency (13.72 %) is achieved when the TiO2 ETL is depositedat 200 ℃ with 15 nm - thickness, which shows a great decrease when comparedwith the TiO2 ETL fabricated by sol-gel method. Notably, by using ALD-SnO2 asthe ETL, the efficiency of the PSC increases to 17.46 %. Moreover, thehysteresis phenomenon of the PSC is greatly improved. Maybe the matched energylevel of SnO2 and MAPbI3 can account for the beneficial role of ALD-SnO2, whichwould facilitate the electron extraction and reduce the possibility of carriesrecombination at the SnO2/MAPbI3 interface.

(4) PERC solar cell passivated on thebackside with AlOx and SiNx is introduced to construct the perovskite/siliconfour-terminal tandem solar cell.

关键词:晶界钝化;溶剂工程;钙钛矿/硅叠层电池;SiNWs陷光结构

grain boundary passivationg; solventengineering; perovskite/silicon tandem solar cells; light trapping by SiNW

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