Abstract
Squaraine dyes have shown promising properties for high performance organic solar cells owing to their advantages of intense absorption and high absorption coefficients in the visible and near-infrared (NIR) regions. In this work, to directly compare the photovoltaic performance of solution- and vacuum-processed small-molecule bulk heterojunction (SMBHJ) solar cells, we employed a squaraine small molecular dye, 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ), as an electron donor combined with fullerene acceptors to fabricate SMBHJ cells either from solution or vacuum deposition process. The solution-processed SMBHJ cell possesses a power conversion efficiency (PCE) of ~4.3%, while the vacuum-processed cell provides a PCE of ~6.3%. Comparison of the device performance shows that the vacuum-processed SMBHJ cells possess higher short-circuit current density, fill factor and thus higher PCE than the solution-processed devices, which should be assigned to more efficient charge transport and charge extraction in the vacuum-processed SMBHJ cells. However, solution-processed SMBHJ cells demonstrate more pronounced temperature-dependent device performance and higher device stability. This study indicates the great potential of DIBSQ in photovoltaic application via both of solution and vacuum processing techniques.
Highlights
Organic solar cells (OSCs) have attracted much attention as a green solar energy technology for cost-effective, renewable energy sources because of their advantages of low-cost, light-weight, large-area manufacturing, and mechanical flexibility (Yu et al, 1995; Günes et al, 2007; Li et al, 2012; He et al, 2015; Duan et al, 2017)
The only difference is the fabrication processing and the corresponding acceptor materials used for the photoactive layers: the solution-processed DIBSQ:phenyl-C71-butyric acid methyl ester (PC71BM) small-molecule bulk heterojunction (SMBHJ) cells were prepared by spin-coating the DIBSQ:PC71BM blend solution, while the vacuum-processed DIBSQ:C70 SMBHJ cells were fabricated by co-evaporating the DIBSQ and C70 in the vacuum condition
To directly compare the device performance of solution- and vacuum-processed SMBHJ solar cells, we employed a SQ dye, which can be deposited by using both of the solution and vacuum processing, as electron donor combined with fullerene as acceptor to construct solutionand vacuum-processed DIBSQ:Fullerene SMBHJ cells
Summary
Organic solar cells (OSCs) have attracted much attention as a green solar energy technology for cost-effective, renewable energy sources because of their advantages of low-cost, light-weight, large-area manufacturing, and mechanical flexibility (Yu et al, 1995; Günes et al, 2007; Li et al, 2012; He et al, 2015; Duan et al, 2017). This unique property of DIBSQ indicates the photoactive layers of the DIBSQ:Fullerene based SMBHJ cells can be fabricated by spin-coating DIBSQ:PC71BM mixed solution or by vacuum co-evaporation of DIBSQ and C70, which offers the possibility to directly compare the device performance of two processing techniques.
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