Liangzheng Zhu

High Consistency Perovskite Solar Cell with a Consecutive Compact and Mesoporous TiO2 Film by One-Step Spin-Coating

Generally, in classic mesoscopic perovskite solar cells (PSCs), the compact blocking layer and mesoporous scaffold layer prepared by two steps or more will inevitably form an interface between them. It is undoubted that the interface contact is not conducive to electron transport and would increase the recombination in the device, resulting in the inferior performance of PSCs. In this work, we constructed a consecutive compact and mesoporous (CCM) TiO2 film to substitute the compact blocking layer and scaffold layer for mesoscopic PSCs. The bottom of the CCM TiO2 film was dense and the top was mesoporous with large uniform macropores. The two parts of the film were consecutive, which could promote the electron transport rate and decrease the charge recombination effectively. Moreover, due to the existence of macropores in the CCM TiO2 film, it was propitious to the deposition of perovskite and charge separation for the perovskite layer. Over 15.0% of average power conversion efficiency (PCE) with high consistency photovoltaic performances was achieved for the CCM TiO2 film based mesoscopic PSCs, which is higher than that with a classic mesoporous structure.

Enhancing the Photovoltaic Performance of Perovskite Solar Cells with a Down-Conversion Eu-Complex

Organometal halide perovskite solar cells (PSCs) have shown high photovoltaic performance but poor utilization of ultraviolet (UV) irradiation. Lanthanide complexes have a wide absorption range in the UV region and they can down-convert the absorbed UV light into visible light, which provides a possibility for PSCs to utilize UV light for higher photocurrent, efficiency, and stability. In this study, we use a transparent luminescent down-converting layer (LDL) of Eu-4,7-diphenyl-1,10-phenanthroline (Eu-complex) to improve the light utilization efficiency of PSCs. Compared with the uncoated PSC, the PSC coated with Eu-complex LDL on the reverse of the fluorine-doped tin oxide glass displayed an enhancement of 11.8% in short-circuit current density (Jsc) and 15.3% in efficiency due to the Eu-complex LDL re-emitting UV light (300-380 nm) in the visible range. It is indicated that the Eu-complex LDL plays the role of enhancing the power conversion efficiency as well as reducing UV degradation for PSCs.

Enhanced performance and stability of perovskite solar cells using NH4I interfacial modifier

Despite organic-inorganic hybrid perovskite solar cells have rapid advances in power conversion efficiency in recent years, the serious instability of the device under practical working conditions is the current main challenge for commercialization. In this study, we have successfully inserted NH4I as an interfacial modifier between the TiO2 electron transport layer and perovskite layer. The result shows that it can significantly improve the quality of the perovskite films and electron extraction efficiency between the perovskite and electron transport layer. The devices with NH4I are obtained an improved power conversion efficiency of 18.31% under AM 1.5G illumination (100 mW cm-2). More importantly, the humidity and UV light stability of the devices are greatly improved after adding NH4I layer. The uncoated devices only decrease by less than 15% of its original efficiency during 700-h stability tests in a humidity chamber (with a relative humidity of 80%) and the efficiency almost maintains 70% of its initial value over 20 h under UV light stress tests. This work provides a potential way by interfacial modification to significantly improve photovoltaic performance and stability of perovskite solar cells.