| 초록 |
Perovskite solar cells based on the organometal halides (e.g. methylammonium lead iodide; MAPbI3) have been investigated very intensively owing to their skyrocketing conversion efficiencies. The perovskite solar cells can be classified either as a n-i-p type or as a p-i-n type depending on the direction of charge collection. Among them, the p-i-n type devices especially with a planar structure have advantages such as simple and low-temperature processes compatible with flexible substrates, negligible hysteresis effect, and potential tandem configuration with other highly efficient inorganic solar cells. However, the p-i-n type planar devices have issues of lower conversion efficiency compared with the n-i-p type counterparts and poor stability resulting from the use of organic hole-extraction layers. In this study, we successfully demonstrate highly efficient p-i-n type planar perovskite solar cells with inorganic NiO-based hole-extraction layer. Factors that govern the solar cell performance of the NiO-based perovskite solar cells have been investigated systematically, especially regarding their influences on the fill factor. It has been found that the conductivity of the hole-extraction layer and its physical/electrical contact with the perovskite layer are very important for the device performance. It has been also found that the long-term stability of the perovskite solar cells has been significantly enhanced by replacing the conventional organic PEDOT:PSS layer with the inorganic hole-extraction layer. As a result, the best NiO-based device exhibits a high conversion efficiency close to 20% with no hysteresis effect, which is the best efficiency among the p-i-n type planar devices. |
