Study on the Characteristics of Photovoltaic and Field Effect of Small Molecule Donors

Two benzothiadiazole (BT) small molecule donors (namely D1 and D2) were designed and synthesized. We studied their photovoltaics properties and filed effect properties. It is found that the best power conversion efficiency (PCE) of the organic solar cells (OSCs) was 6.87% based on the D2: IDIC-4F (the donor/acceptor(D/A) ratio is 1:1). In contrast, the device of D1: IDIC-4F (the D/A ratio is 1:1) only shows PCE value of 2.41%. This is because that the crystallization property of the material is improved by the changing of side chain group, which is beneficial to the improvement of the morphology of the donor material. Moreover, the introduction of side chain greatly improves the external quantum efficiency (EQE) of D2 based solar cell. Also, we fabricated the organic field effect transistors (OFETs) with D1 and D2 as semiconductor layer, and n-octadecylphosphonic acid (ODPA) as self-assembled monolayers (SAMs), as a result, the hole motilities of the devices are
${1.21}\times {10} ^{-{2}}$
cm
$^{{2}}\text{v}^{-{1}}\text{s}^{-{1}}$
for D1 and
${1.25}\times {10} ^{-{2}}$
cm
$^{{2}}\text{v}^{-{1}}\text{s}^{-{1}}$
for D2, respectively.