Absence of Photoinduced Charge Transfer in Blends of PbSe Quantum Dots and Conjugated Polymers

Abstract

We use photoluminescence (PL) quenching and photoinduced absorption (PIA) spectroscopy to study charge transfer in bulk heterojunction blends of PbSe quantum dots with the semiconducting polymers poly-3-hexylthiophene (P3HT) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-para-phenylene vinylene] (MDMO-PPV). PIA spectra from the PbSe blends are compared to spectra from similar blends of the polymers with phenyl-C(61)-butyric acid methyl ester (PCBM) and blends with CdSe quantum dots. We find that the MDMO-PPV PL is quenched, and the PL lifetime is shortened upon addition of PbSe quantum dots, while the PL of the P3HT is unaffected upon blending. However, for PbSe blends with both polymers, the PIA spectra show very little polaronic signal, suggesting that few, if any, long-lived charges are being produced by photoinduced charge transfer.

Polymer selection toward efficient polymer/PbSe planar heterojunction hybrid solar cells

“…Polymers can offer high absorbance coefficient and excellent film-forming ability while NCs may provide tunable bandgap across visible to near infrared (NIR) and high carrier mobility [1,2]. A variety of inorganic NCs have been studied in HSCs such as cadmium chalcogenides NCs (CdS [3,4], CdSe [5,6], CdTe [7,8]) and lead chalcogenides NCs (PbS [9][10][11], PbSe [12], PbSSe [13]). Compared to cadmium chalcogenides, PbS and PbSe have significant larger exciton Bohr radii (PbS 20 nm, PbSe 46 nm, CdSe 6 nm) [14] and hence demonstrate higher carrier mobility (PbSe 0.9-7 cm À2 V À1 S À1 [15][16][17][18], CdSe $10 À2 cm À2 V À1 S À1 [19]) even without high temperature sintering.…”

Hybrid solar cells based on poly(3-hexylthiophene) and electrospun TiO2 nanofibers modified with CdS nanoparticles

“…However, low carrier mobilities and poor stability of the active layers hinder the practical applications of the devices [3][4][5]. Many researchers attempted to overcome this problem by replacing the organic electron transporter with inorganic semiconductors [10][11][12][13][14][15], such as CdSe, TiO 2 and ZnO, because the n-type semiconductors Chinese Materials Research Society www.elsevier.com/locate/pnsmi www.sciencedirect.com exhibit more stable physical and chemical properties. Furthermore, those semiconductors possess several advantages over their organic counterparts, including high electron mobility, high dielectric constant and facile control of the size and the shape of nanostructure.…”

“…Furthermore, those semiconductors possess several advantages over their organic counterparts, including high electron mobility, high dielectric constant and facile control of the size and the shape of nanostructure. Therefore, inorganic nanoparticles [15], nanorods [14,[16][17][18][19], nanofibers [12,13,20,21] and porous films [11,22] have been popularly used in hybrid solar cells. Various techniques have been employed to improve the interfacial area and the properties of the organicinorganic heterojunctions [13,22].…”

In-Gap State of Lead Chalcogenides Quantum Dots

“…We therefore assign G.S a state for trapped exciton. Such a state, due to its long lifetime (~ several s), is relevant to exciton dissociation and carrier extraction processes in QD/polymer composite, a material system potentially can be utilized for low-cost high efficiency solar cells [7,42]. Figure 7 is a schematic drawing of a QD/polymer composite.…”