Charge transport and its characterization using photo-CELIV in bulk heterojunction solar cells

Abstract

This mini-review gives a simple overview of the workings of organic photovoltaic (OPV) devices, the way in which charge transfer occurs through the active layers, and then introduces how photo-induced charge carrier extraction by linearly increasing voltage (photo-CELIV) and time of flight (TOF) techniques can be employed to give comprehensive indications of charge carrier mobility, density and recombination in OPVs. It is shown how photo-CELIV and TOF characterizations, using extraction current transients, can give an understanding of degradation mechanisms through observation of the trapping of charge carriers and bimolecular recombination. Examples of deployment and the interpretation of the results are given. It is hoped that this brief introduction will serve as a stepping stone into more in-depth papers and books and encourage wider use of photo-CELIV and TOF technologies which can be employed with whole devices.

Burn‐in Free Nonfullerene‐Based Organic Solar Cells

“…This allows to estimate the maximum generation rate of free charge carriers G max according to J sat = qG max L, where q is the electronic charge and L is the active layer thickness. For this purpose, we investigated the charge carrier mobility (μ) of solar cells by employing the technique of photoinduced charge carrier extraction by linearly increasing voltage (photo-CELIV [38] ) (see the Experimental Section for further details). The enhancement of G max is consistent with the improved J sc values extracted under solar simulator illumination after photo degradation.…”

Overcoming Microstructural Limitations in Water Processed Organic Solar Cells by Engineering Customized Nanoparticulate Inks

“…Most interestingly, we find that the total collected charge (Q tot ) as function of applied prebias (V pre ) is following the similar trend for both, HS and NP devices. [56] By fitting the curves in Figure S17d in the Supporting Information, n(0), τ B and γ for the two NP and the HS systems are extracted and summarized in Table 2. The HS system exhibits a similar Q tot loss behavior with losses of 8% and 10%, respectively, revealing that geminate recombination is fairly comparable in these systems.…”

Fluctuations in the Emission Polarization and Spectrum in Single Chains of a Common Conjugated Polymer for Organic Photovoltaics

“…Light is primarily absorbed by the conjugated polymer in a solar cell blend, and thus the polymer's physical and electronic properties are of significant interest as they ultimately control the device efficiency. The chain alignment, degree of aggregation, and nature of the excited states play a role in light absorption, exciton diffusion to the donor–acceptor interface, charge separation, and finally charge extraction . These properties of conjugated polymers are often hard to measure and are interdependent upon each other, such that a clear and fully understood microscopic picture is rarely achieved.…”