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3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic – organic hybrid perovskite solar cells

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ABSTRACT

The ever increasing demand for clean energy has encouraged researchers to intensively investigate environmentally friendly photovoltaic devices. Inorganic–organic hybrid perovskite solar cells (PSCs) are very promising due to their potentials of easy fabrication processes and high power conversion efficiencies (PCEs). Designing hole-transporting materials (HTMs) is one of the key factors in achieving the high PCEs of PSCs. We now report the synthesis of two types of carbazole-based polymers, namely 3,6-Cbz-EDOT and 2,7-Cbz-EDOT, by Stille polycondensation. Despite the same chemical composition, 3,6-Cbz-EDOT and 2,7-Cbz-EDOT displayed different optical and electrochemical properties due to the different connectivity mode of the carbazole unit. Therefore, their performances as hole-transporting polymeric materials in the PSCs were also different. The device based on 2,7-Cbz-EDOT showed better photovoltaic properties with the PCE of 4.47% than that based on 3,6-Cbz-EDOT. This could be due to its more suitable highest occupied molecular orbital (HOMO) level and higher hole mobility.

No MeSH data available.


(a) Current density–voltage curves and (b) incident photon to current conversion efficiency (IPCE) spectra for PSCs with different HTMs under AM1.5G illumination at 100 mW cm−2.
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Figure 3: (a) Current density–voltage curves and (b) incident photon to current conversion efficiency (IPCE) spectra for PSCs with different HTMs under AM1.5G illumination at 100 mW cm−2.

Mentions: Fig. 3 shows the current density–voltage (J–V) curves for the devices based on 3,6-Cbz-EDOT, 2,7-Cbz-EDOT, and P3HT. The device performance parameters are summarized in Table 2. Among the three devices, the device based on 2,7-Cbz-EDOT displayed the highest power conversion efficiency (PCE) of 4.47% with a short-circuit current density (JSC) of 16.5 mA cm−2, open circuit voltage (VOC) of 0.81 V, and fill factor (FF) of 0.33. The lower PCE (3.90%) of the device based on 3,6-Cbz-EDOT was mainly due to the lower JSC (14.7 mA cm−2), which would be reflected in the absorption range and hole mobility of the HTMs [43]. In addition, it was postulated that the deeper HOMO level of 2,7-Cbz-EDOT facilitated the hole extraction from the valence band of the perovskite layer [44]. Moreover, it should be noted that 2,7-Cbz-EDOT outperforms the benchmark p-type semiconducting polymer, P3HT, despite almost the same HOMO levels.


3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic – organic hybrid perovskite solar cells
(a) Current density–voltage curves and (b) incident photon to current conversion efficiency (IPCE) spectra for PSCs with different HTMs under AM1.5G illumination at 100 mW cm−2.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979756&req=5

Figure 3: (a) Current density–voltage curves and (b) incident photon to current conversion efficiency (IPCE) spectra for PSCs with different HTMs under AM1.5G illumination at 100 mW cm−2.
Mentions: Fig. 3 shows the current density–voltage (J–V) curves for the devices based on 3,6-Cbz-EDOT, 2,7-Cbz-EDOT, and P3HT. The device performance parameters are summarized in Table 2. Among the three devices, the device based on 2,7-Cbz-EDOT displayed the highest power conversion efficiency (PCE) of 4.47% with a short-circuit current density (JSC) of 16.5 mA cm−2, open circuit voltage (VOC) of 0.81 V, and fill factor (FF) of 0.33. The lower PCE (3.90%) of the device based on 3,6-Cbz-EDOT was mainly due to the lower JSC (14.7 mA cm−2), which would be reflected in the absorption range and hole mobility of the HTMs [43]. In addition, it was postulated that the deeper HOMO level of 2,7-Cbz-EDOT facilitated the hole extraction from the valence band of the perovskite layer [44]. Moreover, it should be noted that 2,7-Cbz-EDOT outperforms the benchmark p-type semiconducting polymer, P3HT, despite almost the same HOMO levels.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

The ever increasing demand for clean energy has encouraged researchers to intensively investigate environmentally friendly photovoltaic devices. Inorganic–organic hybrid perovskite solar cells (PSCs) are very promising due to their potentials of easy fabrication processes and high power conversion efficiencies (PCEs). Designing hole-transporting materials (HTMs) is one of the key factors in achieving the high PCEs of PSCs. We now report the synthesis of two types of carbazole-based polymers, namely 3,6-Cbz-EDOT and 2,7-Cbz-EDOT, by Stille polycondensation. Despite the same chemical composition, 3,6-Cbz-EDOT and 2,7-Cbz-EDOT displayed different optical and electrochemical properties due to the different connectivity mode of the carbazole unit. Therefore, their performances as hole-transporting polymeric materials in the PSCs were also different. The device based on 2,7-Cbz-EDOT showed better photovoltaic properties with the PCE of 4.47% than that based on 3,6-Cbz-EDOT. This could be due to its more suitable highest occupied molecular orbital (HOMO) level and higher hole mobility.

No MeSH data available.