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Performance Enhancement of Bulk Heterojunction Solar Cells with Direct Growth of CdS‐Cluster‐Decorated Graphene Nanosheets
Author(s) -
Yuan Kai,
Chen Lie,
Tan Licheng,
Chen Yiwang
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201400119
Subject(s) - materials science , nanosheet , graphene , chemical engineering , energy conversion efficiency , heterojunction , photoactive layer , polymer solar cell , charge carrier , nanotechnology , optoelectronics , engineering
Two‐dimensional graphene–CdS (G–CdS) semiconductor hybrid nanosheets were synthesized in situ by graphene oxide (GO) quantum wells and a metal–xanthate precursor through a one‐step growth process. Incorporation of G–CdS nanosheets into a photoactive film consisting of poly[4,8‐bis‐(2‐ethyl‐hexyl‐thiophene‐5‐yl)‐benzo[1,2‐ b :4,5‐ b ]dithiophene‐2,6‐diyl]‐ alt ‐[2‐(2‐ethyl‐hexanoyl)‐thieno[3,4‐ b ]thiophen‐4,6‐diyl] (PBDTTT‐C‐T) and [6,6]‐phenyl C 70 butyric acid methyl ester (PC 70 BM) effectively decreases the exciton lifetime to accelerate exciton dissociation. More importantly, the decreasing energy levels of PBDTTT‐C‐T, PC 70 BM, and G–CdS produces versatile heterojunction interfaces of PBDTTT‐C‐T:PC 70 BM, PBDTTT‐C‐T:G–CdS, and PBDTTT‐C‐T:PC 70 BM:G–CdS; this offers multi‐charge‐transfer channels for more efficient charge separation and transfer. The charge transfer in the blend film also depends on the G–CdS nanosheet loadings. In addition, G–CdS nanosheets improve light utilization and charge mobility in the photoactive layer. As a result, by incorporation of G–CdS nanosheets into the active layer, the power‐conversion efficiency of inverted solar cells based on PBDTTT‐C‐T and PC 71 BM is improved from 6.0 % for a reference device without G–CdS nanosheets to 7.5 % for the device with 1.5wt % G–CdS nanosheets, due to the dramatically enhanced short‐circuit current. Combined with the advantageous mechanical properties of the PBDTTT‐C‐T:PC 70 BM:G–CdS active layer, the novel CdS‐cluster‐decorated graphene hybrid nanomaterials provide a promising approach to improve the device performance.