Solvent-resistant small molecule solar cells by roll-to-roll fabrication via introduction of azide cross-linkable group

• Diketopyrrolopyrrole derivative with cross-linkable azide groups was designed and synthesized.
• A solvent-resistant molecule was emerged after cross-linking.
• Solar cells employing the target molecule as either electron donor or acceptor were fabricated by roll coating.
• This was the first report of small molecule solar cells with large area by roll-to-roll processing.

A novel cross-linkable azide-functionalized diketopyrrolopyrrole based compound DPP(BT-N3)2 was designed and synthesized via Stille coupling. Cross-linking of such molecule could help us fabricate insoluble film which could be used to fabricate heterostructures through solution processing, without dissolving the pre-patterned layers. In order to investigate the photovoltaic performances of the newly synthesized compound, large area solar cells were produced by roll coating technique. Two set of devices were fabricated by employing DPP(BT-N3)2 as either an electron donor or acceptor. A best power conversion efficiency of 0.067%, combined with an open circuit voltage of 0.53 V, and a fill factor of 37.6% were obtained for the device with DPP(BT-N3)2 as an electron acceptor. In addition, we could prove that the large area small molecule based organic solar cells could be fabricated using roll coating, which could be used in the industries for large-scale of production.

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