Electroluminescence imaging of organic photovoltaic modules

Abstract

We report on electroluminescence (EL) imaging of organic photovoltaic cells and modules with poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester as semiconductor layer. The dominant EL emission is found in a spectral regime between 1200 and 1400 nm and is identified as the radiative decay of the charge transfer complex formed between the polymer and the fullerene. Electroluminescence emission from the pristine compounds is either much weaker or completely absent. Overall, electroluminescence imaging is shown to give valuable information on the defects but also on the performance of organic solar modules.

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

“…The cells were irradiated with a light-emitting diode (LED) solar simulator featuring an AM1.5G spectrum at 1000 W m −2 (FUTURELED GmbH, Berlin, Germany). [ 74 ] The intensity of the LEDs was calibrated using an ISE Fraunhofer certifi ed silicon photodiode.…”

Discriminating bulk versus interface shunts in organic solar cells by advanced imaging techniques

“…Using different excitation methods may yield quantitatively and qualitatively different results because EL is sensitive to the charge extraction/injection into the active layer (AL) as well as to the integrity of the AL itself, while PL only probes the AL . Luminescence imaging and LIT have been used for characterization of both classic crystalline silicon photovoltaics as well as characterization of novel thin‐film photovoltaics like OPV or hybrid perovskite solar cells …”

“…[11][12][13] Using different excitation methods may yield quantitatively and qualitatively different results because EL is sensitive to the charge extraction/injection into the active layer (AL) as well as to the integrity of the AL itself, while PL only probes the AL. 14,15 Luminescence imaging and LIT have been used for characterization of both classic crystalline silicon photovoltaics [16][17][18] as well as characterization of novel thin-film photovoltaics like OPV [19][20][21][22] or hybrid perovskite solar cells. [23][24][25] Visualizing the position of defects is the major strength of imaging methods; however, depth resolution allowing the determination of the vertical position of a defect (ie, in which layer of the thin-film device a defect is located) is majorly limited.…”

Influence of energetic disorder on electroluminescence emission in polymer:fullerene solar cells

“…In addition, it is relevant for deriving information about the density of available states from EL and quantum efficiency measurements as well as for the analysis of devices with EL imaging. Being already an established and popular technique in the field of inorganic photovoltaics and just an emerging technique for organic devices, 25,26 EL imaging on thin film modules can yield valuable information on resistive effects like shunts and the series resistance of the transparent conductive oxides employed. 37,65 The quantitative analysis of EL images in inorganic photovoltaics relies on the fact that the radiative recombination flux scales with exp(qV /kT ), i.e., that the radiative ideality factor is one.…”

“…[10][11][12][13][14][15][16][17] In these materials, disorder creates localized states or traps that have a strong effect on transport and likely also on nonradiative recombination. 10,[18][19][20] Recently, electroluminescence (EL) spectroscopy [21][22][23][24] and imaging 25,26 have been introduced as a novel (for organic semiconductors) characterization tool to study the energy levels as well as recombination and defects in polymer:fullerene solar cells. While the theoretical framework [27][28][29][30] to describe EL emission is well developed for the case of inorganic, crystalline pn-junction solar cells, the question of how applicable classical semiconductor theories are for disordered and, in this case, organic semiconductors is still under debate.…”