Photoinduced electron and hole transfer in CdS:P3HT nanocomposite films: effect of nanomorphology on charge separation yield and solar cell performance

Abstract

The influence of morphology on the photophysical properties of blend films containing in situ grown CdS and poly(3-hexylthiophene-2,5-diyl) (P3HT), fabricated utilising a metal xanthate single source precursor, is reported. A combination of transient absorption spectroscopy (TAS), transmission electron microscopy (TEM) and photovoltaic device measurements are employed to study the relationship between the efficiency of charge separation, photocurrent generation and thin film morphology. We identify that a significant proportion of the extractable charge originates from the direct excitation of CdS followed by hole-transfer to the P3HT polymer. The yield of this hole-transfer step from the inorganic CdS to the organic polymer is largely unaffected by the film's nanomorphology, while the dissociation of P3HT excitons into free charges at the CdS:P3HT interface is found to be strongly dependent on this parameter with high yields of charge transfer only being achieved at high CdS loadings. The present study elucidates design rules for the optimization of hybrid inorganic-organic solar energy conversion devices.

Surface Charge Transfer Doping of Low‐Dimensional Nanostructures toward High‐Performance Nanodevices

“…The lack of complementary doping seriously hampers the practical application of group‐II–VI semiconductors, as p–n homojunctions are the basic element for high‐performance electronic and optoelectronic devices . To bypass the difficulty, group‐II–VI semiconductor nanostructure‐based devices are normally fabricated with device structures like heterojunctions, Schottky junctions, or organic–inorganic hybrid structures . Nevertheless, the interfacial defects, inferior stability of organic materials, and energy‐level mismatch between hetero‐semiconductors inhibit the improvement of the device performance.…”

Inorganic Quantum Dot Materials and their Applications in “Organic” Hybrid Solar Cells

“…In contrast to ultrafast electron transfer, hole transfer from QDs to polymer occurs at a much slower rate, up to at least 1 ns after excitation . In addition, the hole transfer yields are found to be less correlated with loading ratio of polymer/QDs . At high QD loading ratio the polymer has been found to agglomerate, leading to polymer‐rich domains, insufficient exciton dissociation and poor hole transport.…”

“…[39] In addition, the hole transfer yields are found to be less correlated with loading ratio of polymer/QDs. [40] At high QD loading ratio the polymer has been found to agglomerate, leading to polymer-rich domains, insufficient exciton dissociation and poor hole transport. While at high polymer concentration QDs tend to aggregate instead, resulting in inefficient charge separation and correspondingly low electron transport.…”

A comprehensive review of the application of chalcogenide nanoparticles in polymer solar cells

“…Dowland et al 111 combined the morphology information with transient absorption spectroscopy (TAS) data to correlate charge generation with morphology. Firstly it was demonstrated that the nanomorphology may be controlled by altering the relative amounts of active layer components in CdS:P3HT lms prepared by the in situ decomposition of a xanthate precursor of CdS.…”

“…The presence of traps on the nanoparticle surface, either by incomplete ligand coverage or by oxidation, can also affect charge generation and charge transport, therefore increasing charge recombination. Dowland et al 111 combined the morphology information with transient absorption spectroscopy (TAS) data to correlate charge generation with morphology. Firstly it was demonstrated that the nanomorphology may be controlled by altering the relative amounts of active layer components in CdS:P3HT lms prepared by the in situ decomposition of a xanthate precursor of CdS.…”