Defect engineering is an effective approach to improving the efficiency of solar energy conversion devices by tuning the material electronic and optical properties. My thesis focus on developing effective and stable solar energy conversion devices from the viewpoint of defect engineering. The first part is on PEC water splitting devices. The insufficient light absorption and short carrier diffusion length have limited the performance of PEC water splitting devices. Here, I introduce an element doping method to prepare metal doped WO₃ photoanode. Improved performance has been witnessed after doping, which is not only due to the increased light absorption and also doping increased charge carrier densities. The second part is on perovskite solar cells (PVSC), which have been develo...[ Read more ]

Defect engineering is an effective approach to improving the efficiency of solar energy conversion devices by tuning the material electronic and optical properties. My thesis focus on developing effective and stable solar energy conversion devices from the viewpoint of defect engineering. The first part is on PEC water splitting devices. The insufficient light absorption and short carrier diffusion length have limited the performance of PEC water splitting devices. Here, I introduce an element doping method to prepare metal doped WO₃ photoanode. Improved performance has been witnessed after doping, which is not only due to the increased light absorption and also doping increased charge carrier densities. The second part is on perovskite solar cells (PVSC), which have been developed rapidly in recent years. Currently, the practical application of PVSCs is hindered by the following obstacles: slow photoresponse (hysteresis, light soaking) and fast degradation. Here, I validate a simple model to relate the scan rate-dependent hysteresis of the solar cell and the defect assisted ion migration in perovskite materials. High performance hysteresis free PVSCs can be prepared through suppressing the defect migration in PVSCs. Moreover we find out that the defect in the perovskite materials also contribute to the degradation of the PVSC devices. Introducing polar FA⁺ with larger ionic radius instead of the commonly used MA⁺ might be an effective approach to improving the stability of PVSCs. To be continued, we demonstrate that the light soaking effect (LSE) observed in inverted perovskite solar cells is due to ion migration and can be effective suppressed by tuning the defect (ion) migration in the devices. Finally future directions and perspective frontiers relating to defect engineering for effective solar energy conversion devices are discussed and highlighted.