Efficient semitransparent organic solar cells with good color perception and good color rendering by blade coating

This paper proposes high efficiency semitransparent organic solar cells (OSCs) with good color perception and good color rendering using blade coating technique. We investigate four different polymer blends and first fabricate small area devices with active area of 0.04 cm², followed by large area devices with active area of 10.8 cm². Two of the polymer blends, 2,6-Bis(trimethyltin)-4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene:6,6-phenyl C71-butyric acid methyl ester (PBDTTT-CT:PC₇₁BM) and poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b'] dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]:PC₇₁BM (PBDTTT-EFT:PC₇₁BM) show promising results. For small area devices, semitransparent PBDTTT-CT:PC₇₁BM and semitransparent PBDTTT-EFT:PC₇₁BM achieve a power conversion efficiency (PCE) of 5.2% (opaque PCE = 7.5%) and 5.6% (opaque PCE = 9.4%) respectively. For large area devices, they are found to produce a PCE of 3.8% (opaque PCE = 4.2%) and 5.3% (opaque PCE = 5.9%) respectively. Based on the CIE 1931 chromaticity diagram, semitransparent PBDTTT-CT:PC₇₁BM and semitransparent PBDTTT-EFT:PC₇₁BM are located very close to the standard illuminant D65, indicating good color perception. As for color rendering, they demonstrate high color rendering index (CRI) of 95.4 and 87.1 respectively. These combined high performances indicate high-quality transmitted light, which is suitable for window application.