Research On Charge Selective Collection Layers For Perovskite Solar Cells

As a new type of 3rd-generation solar cells, perovskite solar cells (PSCs) has aroused many attentions immediately after its first appearance. For PSCs, high quality charge selective-collection layer, which is of great significance in terms of obtaining high PCE, includes two types, namely electron selective-collection layer (ESL) and that for hole (HSL). Usually, TiO2 thin film is used as ESL though its conductivity is relatively low. Studies show that PCE of PSCs can be improved with increase in conductivity of TiO2 ESL. Thus, it is necessary to replace TiO2 using some other candidates with higher conductivity. SnO2 is more advantageous in terms of conductivity when compared to TiO2. On the other hand, it is very effective to improve the stability and reduce production costs of the PSCs devices by replacing unstable organic hole transport material (HTM) and expensive noble metal electrodes, very favorable for PSCs industrialization as soon as possible. Conductive carbon materials are cheap, stable and can be well responsible for collecting holes selectively. Thus, replacing HTM and noble metal electrodes with conductive carbon is of great value for practical applications. In this thesis, we focus on fabrications of novel charge selective collection layers, integrating them into cell devices and giving deep insights into the effects of their peroperties on the photovoltaic performances of PSCs.Nanocrystalline SnO2 thin film was prepared by sol-gel and characterized by SEM and XRD. Results indicated that SnO2 thin film was composed of small sized tetragonal rutile nanocrystals. We applied the SnO2 compact thin layer into PSCs and compared with that based on TiO2 thin layer. It was indicated that, compared to the conventional TiO2-based PSCs, the SnO2-based PSCs showed higher short-circuit current density, lower open-circuit voltage and fill factor, finally leading to slight lower conversion efficiency. It was thought that, in SnO2-based PSCs, the charge recombination was more serious. Furthermore, it was found that, for SnO2-based PSCs, their final photovoltaic performances were highly dependent upon the mensuration means, which have been investigated and discussed in detail.Secondly, conductive carbon black was adopted to replace the organic HTM and the noble metal electrodes. By a simple spraying method, carbon black layer was made onto cathode for hole collection, the effects of film thickness, as well as the contact interface between carbon layer and that of perovskite on cell performance were studied. Meanwhile, the effect of thermal treating on cell performance was also studied, it indicated that PCE of PSCs could be improved obviously after thermal treating under some specific conditions. In addition, measurement means were also found to influence the cell performance a lot. Through various optimizations, our carbon-based PSCs gave a maximum PCE of 8.42%. By contrast with conventional PSCs, carbon-based PSCs have low production cost and simple production process, our researches laid a good foundation for further study.