Hybrid Organic-Inorganic perovskite solar cells (PVSCs) are a new type of thin-film solar cells based on inorganic-organic hybrid metal halide active materials. Perovskites show many distinctive advantages, such as strong light absorption, small exciton binding energy, adjustable optical band gap, high charge carrier mobility, long charge carrier lifetime, and solution processability. Therefore, PVSCs, with perovskite as the light absorption layer, exhibit excellent photovoltaics performance. The inverted PVSCs can form films at low temperatures and lower the production cost, providing the possibility for the commercial development of flexible devices. High-mobility charge transport layers can improve exciton separation and reduce carrier recombination, which is essential to obtain high...[ Read more ]

Hybrid Organic-Inorganic perovskite solar cells (PVSCs) are a new type of thin-film solar cells based on inorganic-organic hybrid metal halide active materials. Perovskites show many distinctive advantages, such as strong light absorption, small exciton binding energy, adjustable optical band gap, high charge carrier mobility, long charge carrier lifetime, and solution processability. Therefore, PVSCs, with perovskite as the light absorption layer, exhibit excellent photovoltaics performance. The inverted PVSCs can form films at low temperatures and lower the production cost, providing the possibility for the commercial development of flexible devices. High-mobility charge transport layers can improve exciton separation and reduce carrier recombination, which is essential to obtain highly efficient PVSCs. Small molecular HTMs (SM-HTMs) have a well-defined molecular structure and molecular weight, and there is negligible batch-to-batch variation, so the device performance has better reproducibility. In this thesis, the design of SM-HTM, as well as their high-efficiency devices, are discussed by studying four high-efficiency PVSC systems. Firstly, three isomeric HTMs based on distinct dithienothiophene π-bridge were synthesized, suggesting that a small change of the regioisomeric π-bridge structure of D-π-D typed molecules can greatly alter their photophysical properties. A power conversion efficiency (PCE) of 19.23% was achieved with 3T-3. Secondly, a green-solvent-processable hole-transport material M1 enabled by a traditional bidentate ligand 1,10-phenanthroline was synthesized and showed effective perovskite surface passivation, achieving a high PCE of 20.14%. Thirdly, a D-A-D type hole-transport material TPA-FO features an inexpensive aromatic ketone, 9-fluorenone as the core, and enables inverted perovskite solar cells with an efficiency of 20.24%. Our results suggest that constructing SM-HTMs with versatile conjugated planar cores like polythiophenes, 1,10-phenanthroline, and aromatic ketones shows the potential to develop the low-cost, ecofriendly-processable HTMs toward highly efficient PVSCs and give some insight into the structure-property relationship of SM-HTMs.