Pre- or post-TiCl4 treated TiO2 nano-array photoanode for QDSSC: Ti3+ self-doping, flat-band level and electron diffusion length

Abstract

Of the photoanode in QDSSC, the TiCl4 solution treatment is widely used in mesoporous TiO2 surface modification. However, device performance amplification and electron transfer capability improvement of the two common pre- or post treatment are seldom yet. In this work, we explore the TiCl4 different treatments based on the typical TiO2 nanowire array photoanode for CdSxSe1-x QDSSC. In terms of the changes of electron transfer pathway, flat-band potential (Vfb) and charge carrier concentration (ND), we explored the inducement and increase of electron transfer capability and efficacy under different treatments. As for the influence of device performance, the more negative Vfb (−0.315 V, NHE) and higher ND (7.63 × 1019 cm−3) of PBS are beneficial to the increase of open-circuit voltage (Voc) and short-circuit current (Jsc). Therefore, the TiCl4 pre-treatment on photoanode modification (in PBS) is beneficial to reduce the resistances of charge transfer and recombination. The cell performance of PBS in CdSxSe1-x QD sensitization was improved significantly: the PCE was 7.54%, the Jsc was 18.93 mA/cm2, Voc was 0.78 V and fill factor (FF) was 51.1%.