Polymer solar cells (PSCs) were fabricated by combining a diketopyrrolopyrrole-based terpolymer (PTBT-HTID-DPP) as the electron donor, and [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) as the electron acceptor, and the power conversion efficiency (PCE) of 4.31% has been achieved under AM 1.5 G (100 mW cm-2) illumination condition via optimizing the polymer/PC61BM ratio, the variety of solvent and the spin-coating speed. The impact of the spin-coating speed on the photovoltaic performance of the PSCs has been investigated by revealing the effects of the spin-coating speed on the morphology and the absorption spectra of the polymer/PC61BM blend films. When the thickness of the blend films are adjusted by spin-coating a fixed concentration with different spin-coating speeds, the blend film prepared at a lower spin-coating speed shows a stronger absorption per unit thickness, and the correspond device shows higher IPCE value in the longer-wavelength region. Under the conditions of similar thickness, the blend film prepared at a lower spin-coating speed forms a more uniform microphase separation and smaller domain size which leads to a higher absorption intensity per unit thickness of the blend film in long wavenumber band, a larger short-circuit current density (Jsc) and a higher power conversion efficiency (PCE) of the PSC device. Noteworthily, it was found that spin-coating speed is not only a way to control the thickness of active layer but also an influencing factor on morphology and photovoltaic performance for the diketopyrrolopyrrole-based terpolymer.
polymer solar cells device optimization spin-coating speed morphology absorption per unit thickness