In this thesis, we have investigated the operation and fabrication of FACs perovskite solar cells and analysed three different materials that can be used as a hole transport layer in a FACs perovskite solar cell. The materials analysed as hole transport layers are all self-assembled mono-layers and are 2PACz, MeO-2PAcz and Me-4PACz.
Self-assembled monolayers or SAMs used to make the hole transport layers are organic molecules whose main components are a carbazole and a phosphonic group. In addition to being inexpensive to produce, they are transparent and when coated on a substrate, form a hole-selective mono-layer which is only 1 nm thick. These properties make SAMs one of the most promising candidates for hole transport layers in perovskite solar cells of p-i-n configuration.
For the purpose of this thesis, we have fabricated several batches of solar cells, using all three materials for the fabrication of the hole transport layer. The fabricated cells were placed under artificial sunlight, where we measured power conversion efficiency, open circuit voltage, short circuit current and fill factor.
When MeO-2PACz and 2PACz were used, the perovskite showed good wettability on coating. The MeO-2PACz and 2PACz cells achieved conversion efficiencies with very similar mean values above 17% and ranges of values, which made it impossible to determine which of them is better, meaning both materials are suitable candidates as hole transport layers.
Me-4PACz, which has the best conversion efficiency rate in the literature, due to its chemical structure forms a non-polar surface upon being coated on the substrate, which extremely reduces the wettability of the perovskite when coated on the substrate. To resolve this problem, we mixed Me-4PACz with MeO-2PACz, which, when coated on a substrate, forms a layer that exhibits increasingly more polar properties as the concentration of MeO-2PACz in the mixture increases. We found that a mixture of Me-4PACz/MeO-2PACz in a ratio of 25 : 75 exhibited good wetting properties comparable to 2PACz and MeO-2PACz.
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