Abstract
In this work, we studied inverted organic solar cells based on bulk heterojunction using poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PCBM) as an active layer and a novel cathode buffer bilayer consisting of tin dioxide (SnO2) combined with polyethylenimine-ethoxylated (PEIE) to overcome the limitations of the single cathode buffer layer. The combination of SnO2 with PEIE is a promising approach that improves the charge carrier collection and reduces the recombination. The efficient device, which is prepared with a cathode buffer bilayer of 20 nm SnO2 combined with 10 nm PEIE, achieved Jsc = 7.86 mA/cm2, Voc = 574 mV and PCE = 2.84%. The obtained results exceed the performances of reference solar cell using only a single cathode layer of either SnO2 or PEIE.
Highlights
Third-generation photovoltaic technology based on conjugated polymers has drawn much attention over the past decade due to advantages such as simple preparation, light weight, low cost, solution-based fabrication on large-area and low-temperature solution process ability that allows for fabrication on flexible substrates via roll-to-roll manufacturing for solar energy conversion [1,2,3,4]
We demonstrated an efficiency enhancement of inverted organic solar cells based
We demonstrated an efficiency enhancement of inverted organic solar cells based on heterojunction by combining aqueous solution processed PEIE and sputtered SnO2 as a cathode
Summary
Third-generation photovoltaic technology based on conjugated polymers has drawn much attention over the past decade due to advantages such as simple preparation, light weight, low cost, solution-based fabrication on large-area and low-temperature solution process ability that allows for fabrication on flexible substrates via roll-to-roll manufacturing for solar energy conversion [1,2,3,4]. Poly(3,4 ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) has an acidic and hydrophilic nature [16,17], which is detrimental to the active layer and can etch the ITO via the increase of the interfacial resistance through indium diffusion into the active layer; this leads to the deterioration of the device performance [18,19,20] To overcome these issues, the inverted configuration is the appropriate solution to make PEDOT:PSS-free device, where the polarity of charge collection is opposite to that in the conventional one. Courtright et al [36] studied separately PEIE and PEI as the ETL for PBDTT-FTTE:PC70BM-based iOPVs on top of zinc oxide They found that the incorporation of PEIE as a cathode buffer layer gave an enhancement of the cell performance with 7.37%. It has been found that with the combination of SnO2 and PEIE as a cathode buffer bilayer, the short circuit current density (Jsc) was obviously improved, resulting in better device performance with an efficiency reaching 2.84%, compared to reference devices with pure SnO2 and PEIE as a cathode buffer layer
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