Performance Enhancement of Bulk Heterojunction Solar Cells with Direct Growth of CdS‐Cluster‐Decorated Graphene Nanosheets

Abstract

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 C70 butyric acid methyl ester (PC70 BM) effectively decreases the exciton lifetime to accelerate exciton dissociation. More importantly, the decreasing energy levels of PBDTTT-C-T, PC70 BM, and G-CdS produces versatile heterojunction interfaces of PBDTTT-C-T:PC70 BM, PBDTTT-C-T:G-CdS, and PBDTTT-C-T:PC70 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 PC71 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:PC70 BM:G-CdS active layer, the novel CdS-cluster-decorated graphene hybrid nanomaterials provide a promising approach to improve the device performance.

CdS/Graphene Nanocomposite Photocatalysts

“…Furthermore, applications of CdS/graphene based composites in other fi elds including solar cells, [ 280,281 ] biosensors, [282][283][284] Generally, with the introduction of graphene, the CdS/ graphene composites exhibit apparently superior photocatalytic activity and photostability than the bare CdS semiconductor due to the strong synergetic interaction between graphene and the semiconductor.…”

“…Considering the increasing importance of visible light‐driven semiconductor and carbon materials in materials science, there is no doubt that the number of studies concerning the design and application of CdS/graphene based composite photocatalysts will grow fast in the near future. Furthermore, applications of CdS/graphene based composites in other fields including solar cells, biosensors, photovoltaic devices, adsorption, photoelectrochemistry, etc. have also been reported in the past few years.…”

2D Hybrid Nanostructure of Reduced Graphene Oxide–CdS Nanosheet for Enhanced Photocatalysis

“…Special emphasis has been given on designing reduced graphene oxide (RGO)-semiconductor composites [29][30][31][32][33][34][35][36][37][38][39] to improve the efficiency of the catalyst, because the semiconductor materials can be attached with reduced graphene oxide surface and photogenerated electrons can be extracted easily to graphene. Lee et al reported highly photoactive and low band gap TiO 2 − graphene composite.…”

A novel donor–donor polymeric dyad of Poly(3‐hexylthiophene‐block‐oligo(anthracene‐9,10‐diyl): Synthesis, solid‐state packing, and electronic properties

“…An optimal size of phase‐segregated domains is essential whereas very small size of domains may result in nonexistent phase‐pure domains leading to poor device performance. Since it has been established that the size of crystallites is directly influence by the growth rate of the domains in active layer, it is clear that the slow heating of the blend films have provided ideal condition for optimal morphology …”