Enhanced electron lifetime in dye-sensitised solar cells via suppression of electron-hole recombination

Electron-hole recombination is the major problem that reduces the light-electric energy conversion efficiency of photovoltaic devices. We fabricated oxide passivation layers on the surface of transparent conducting oxides (TCO) and photoanodes by using atomic layer deposition (ALD) with the optimised thickness. The intensity-modulated spectroscopy and voltage decay measurements show that the oxide layers, which are considered as blocking layers, effectively reduce the recombination and enhance electron lifetime. Enhanced electron lifetime affects the fill factor and open circuit voltage. With the optimised thickness of the blocking layers, the fill factor and the open circuit voltage were increased by 6% and 14%, respectively. Furthermore, we separated roles of passivation layers on the photoanode and the TCO with open circuit voltage decay (OCVD) measurement. A comparison of the electron recombination characteristics with the oxide layers on the surfaces of NP and the TCO exhibits quite different behaviour, in that the recombination of electrons with higher potential mostly occurs at the surface of NPs, while others with lower potential occur at the surface of TCO.