Rationally Controlled Synthesis of CdSe x Te 1-x Alloy Nanocrystals and Their Application in Efficient Graded Bandgap Solar Cells

• Published in: Nanomaterials (Basel, Switzerland) Vol. 7; no. 11
• Main Authors: Wen, Shiya, Li, Miaozi, Yang, Junyu, Mei, Xianglin, Wu, Bin, Liu, Xiaolin, Heng, Jingxuan, Qin, Donghuan, Hou, Lintao, Xu, Wei, Wang, Dan
• Format: Journal Article
• Language: English
• Published: Switzerland 08.11.2017
• Subjects: nanocrystal; graded bandgap; solar cells; CdTe
• ISSN: 2079-4991

CdSe Te semiconductor nanocrystals (NCs), being rod-shaped/irregular dot-shaped in morphology, have been fabricated via a simple hot-injection method. The NCs composition is well controlled through varying molar ratios of Se to Te precursors. Through changing the composition of the CdSe Te NCs, the spectral absorption of the NC thin film between 570-800 nm is proved to be tunable. It is shown that the bandgap of homogeneously alloyed CdSe Te active thin film is nonlinearly correlated with the different compositions, which is perceived as optical bowing. The solar cell devices based on CdSe Te NCs with the structure of ITO/ZnO/CdSe/CdSe Te /MoO /Au and the graded bandgap ITO/ZnO/CdSe( / )/CdSe /CdTe/MoO /Au are systematically evaluated. It was found that the performance of solar cells degrades almost linearly with the increase of alloy NC film thickness with respect to ITO/ZnO/CdSe/CdSe Te /MoO /Au. From another perspective, in terms of the graded bandgap structure of ITO/ZnO/CdSe/CdSe Te /CdTe/MoO /Au, the performance is improved in contrast with its single-junction analogues. The graded bandgap structure is proved to be efficient when absorbing spectrum and the solar cells fabricated under the structure of ITO/ZnO/CdSe Te /CdSe Te /CdTe/MoO /Au indicate power conversion efficiency (PCE) of 6.37%, a value among the highest for solution-processed inversely-structured CdSe Te NC solar cells. As the NC solar cells are solution-processed under environmental conditions, they are promising for fabricating solar cells at low cost, roll by roll and in large area.