Abstract
The aqueous-based Zn-ammine complex solutions represent one of the most promising routes to obtain the ZnO electron transport layer (ETL) at a low temperature in inverted organic solar cells (OSCs). However, to dope the ZnO film processed from the Zn-ammine complex solutions is difficult since the introduction of metal ions into the Zn-ammine complex is a nontrivial process as ammonium hydroxide tends to precipitate metal salts due to acid-base neutralization reactions. In this paper, we investigate the inverted OSCs with Al-doped-ZnO ETL made by immersion of metallic Al into the Zn-ammine precursor solution. The effects of ZnO layer with different immersion time of Al on film properties and solar cell performance have been studied. The results show that, with the Al-doped-ZnO ETL, an improvement of the device performance could be obtained compared with the device with the un-doped ZnO ETL. The improved device performance is attributed to the enhancement of charge carrier mobility leading to a decreased charge carrier recombination and improved charge collection efficiency. The fabricated thin film transistors with the same ZnO or AZO films confirm the improved electrical characteristics of the Al doped ZnO film.
Highlights
Organic solar cells (OSCs) based on composites of conjugated polymers and fullerene derivatives have attracted more and more attention due to their potential of low cost, light-weight physical features and commercial large area production [1–7]
Very different from the sol-gel method processed zinc oxide (ZnO), to dope the ZnO film processed from the Zn-ammine complex solutions is difficult since the introduction of metal ions into the Zn-ammine complex is a nontrivial process as ammonium hydroxide tends to precipitate metal salts due to acid–base neutralization reaction
We investigate the inverted organic solar cells (OSCs) based on the poly(3-hexylthiophene): phenylC61-butyric acid methyl ester (P3HT:PC61 BM) blend system and the poly({4,8-bis[(2-ethylhexyl)oxy]
Summary
Organic solar cells (OSCs) based on composites of conjugated polymers (electron donor) and fullerene derivatives (electron acceptor) have attracted more and more attention due to their potential of low cost, light-weight physical features and commercial large area production [1–7]. OSCs are mainly fabricated with two structures: the conventional structure and the inverted structure. The long-term stability is a problem because of the degradation of a low-work-function cathode by oxygen and water vapor and the corrosion of ITO by acidic and hygroscopic poly(3,4-ethylenedioxithiophene):poly(styrene sulfonate) (PEDOT:PSS), which is used as the hole transport layer [20–23]. To solve this problem, inverted OSCs have been developed with an improvement in stability and the capability for the roll-to-roll fabrication process. Compared with the Polymers 2018, 10, 127; doi:10.3390/polym10020127 www.mdpi.com/journal/polymers
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