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Overcoming the Limitations of Transient Photovoltage Measurements for Studying Recombination in Organic Solar Cells
Author(s) -
Azzouzi Mohammed,
Calado Philip,
Telford Andrew M.,
Eisner Flurin,
Hou Xueyan,
Kirchartz Thomas,
Barnes Piers R. F.,
Nelson Jenny
Publication year - 2020
Publication title -
solar rrl
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.544
H-Index - 37
ISSN - 2367-198X
DOI - 10.1002/solr.201900581
Subject(s) - charge carrier , optoelectronics , carrier lifetime , transient (computer programming) , organic solar cell , materials science , solar cell , recombination , organic semiconductor , semiconductor , active layer , electron mobility , open circuit voltage , chemical physics , voltage , chemistry , nanotechnology , polymer , physics , silicon , layer (electronics) , computer science , biochemistry , thin film transistor , composite material , gene , operating system , quantum mechanics
Transient photovoltage (TPV) measurements are frequently used to study recombination processes in thin‐film solar cells by probing the decay of a small optically induced voltage perturbation to infer the charge carrier dynamics of devices at open circuit. However, the validity of this method to probe organic semiconductors has recently come into doubt due to large discrepancies in the reported carrier lifetime values for the same systems and the reporting of unrealistic reaction order values. Herein, the validity of TPV to extract reliable charge carrier lifetimes in thin‐film solar cells is explored through the use of time‐dependent drift‐diffusion simulations and measurements. It is found that in low‐mobility materials, TPV serves primarily as a probe of charge carrier redistribution in the bulk rather than bulk recombination dynamics and that the extracted time constant is highly mobility dependent. To address this shortcoming, transient photocharge, a new technique to measure the charge carrier density during photovoltage decay, is introduced and applied to study the recombination dynamics in a series of (fullerene and nonfullerene) organic solar cell systems. It is shown that using this technique the charge carrier recombination lifetime in the active layer is more accurately determined.