A high power conversion efficiency (PCE) of 5.5% was achieved by efficiently incorporating a diketopyrrolopyrrole-based dye with a conducting polymer poly(3,4-ethylenediothiophene) (PEDOT) hole-transporting material (HTM) that was formed in situ, compared with a PCE of 2.9% for small molecular spiroOMeTAD-based solid-state dye solar cells (sDSCs). The high PCE for PEDOT-based sDSCs is mainly attributed to the significantly enhanced charge-collection efficiency, as a result of the three-order-of-magnitude higher hole conductivity (0.53 Scm(-1)) compared with that of the widely used low molecular weight HTM spiro-OMeTAD (3.5 x 10(-4) Scm(-1)).