PROBING CHARGE COLLECTION AND RECOMBINATION DYNAMICS IN ORGANIC SOLAR CELLS BY TRANSIENT PHOTOVOLTAGE AND TRANSIENT ABSORPTION MEASUREMENTS

Florian Günther; Paulo Miranda

Paper Title

Authors

Florian Günther
Paulo Miranda

Modality

Pôster

Subject area

Dispositivos eletrônicos e ópticos (OLED/OFET/OPVs/etc.)

Publishing Date

12/12/2023

Country of Publishing

Brasil

Language of Publishing

Inglês

Paper Page

https://www.even3.com.br/anais/workshop-do-ineo-2023/613073-probing-charge-collection-and-recombination-dynamics-in-organic-solar-cells-by-transient-photovoltage-and-transie

ISBN

978-65-272-0088-8

Keywords

organic solar cells, transient photovoltage, transient photocurrent, transient absorption, P2HT:PCBM

Summary

Improvements in the performances of organic solar cells (OSCs) often depend on the knowledge about the photophysical and electronic processes that occur in the materials. One important issue is charge recombination since it determines losses of photogenerated charges and consequently the overall device efficiency of the whole device. The charge recombination and extraction dynamics in OSCs are usually studied electrically using the transient photovoltage (TPV) and/or transient photocurrent (TPC) techniques. However, in recent years the validity of this method to probe the charge density in the active layer has been questioned because of unrealistic reaction order values deduced from the obtained lifetimes. Since the absorption spectra of free charges in the active layer differ from that of the neutral species, the charge charrier lifetimes can be measured optically by means of transient photoinduced absorption spectroscopy (TAS). In our work, we combine TAS and TPV/TPC to measure both electrical and optical transients simultaneously. Correlating the individual results, it is possible to determine the fate of the photogenerated charges: collection at the contacts vs. recombination within the active layer. In this contribution, results obtained under different experimental conditions for traditional polymer based OSCs (P3HT:PCBM) will be presented. In particular, the intensity of a constant illumination, the load resistance and the excitation pulse intensity were varied. We found that under open circuit condition and high light bias, TPV matches TAS meaning that charge recombination can be studied electrically. In contrast, in dark the TAS signals decay much faster than TPV, indicating that free charges are collected at the contacts, which then discharge with the device RC-constant. Changing the load resistor stepwise from near open-circuit to near short-circuit, the transition between these two cases could be followed. Employing multi-exponential fitting procedures instead of the traditional mono-exponential fit allowed characterize fast versus slow extraction as well as trapping and recombination.

Title of the Event: Workshop do INEO 2023
City of the Event: Nazaré Paulista
Title of the Proceedings of the event: Anais do Workshop INEO 2023
Name of the Publisher: Even3
Means of Dissemination: Meio Digital

How to cite

GÜNTHER, Florian; MIRANDA, Paulo. PROBING CHARGE COLLECTION AND RECOMBINATION DYNAMICS IN ORGANIC SOLAR CELLS BY TRANSIENT PHOTOVOLTAGE AND TRANSIENT ABSORPTION MEASUREMENTS.. In: Anais do workshop INEO 2023. Anais...Nazaré Paulista(SP) Hotel Estância Atibainha, 2023. Available in: https//www.even3.com.br/anais/workshop-do-ineo-2023/613073-PROBING-CHARGE-COLLECTION-AND-RECOMBINATION-DYNAMICS-IN-ORGANIC-SOLAR-CELLS-BY-TRANSIENT-PHOTOVOLTAGE-AND-TRANSIE. Access in: 27/04/2025