Executive Summary : | Renewable energy is becoming an essential part of alternative energy resources. Converting solar energy into electricity using photovoltaic devices is an important and promising avenue to achieve this. Extensive research and development to realize efficient, durable, and affordable solar cell devices is underway to meet the ever-increasing global demand. Organic-inorganic hybrid perovskite solar cells have shown tremendous promise in recent years. However, the materials are highly unstable, thus challenging the fabrication of durable devices. All inorganic perovskites like CsPbI₃ are alternate for organic-inorganic hybrid perovskite materials. However, despite their good optical properties and achievable efficiencies, issues related to stability still persist and need to be addressed. In general inorganic perovskites and perovskite-inspired materials can yield high charge separation by the excitonic process. But charge trap states, low mobility and high electron-phonon coupling suppress the short-circuit current. Alternatively, photoferroelectric materials, which is another class of solar cell material, can generate high voltage due to the intrinsic ferroelectric nature of the material. But, these ferroelectric materials yield low current densities. To harness the best of both material, i.e., high absorption and exciton creation in inorganic halide perovskites, and effective separation of charge carriers through the in-built potential due to ferroelectric domains of ferroelectric oxide perovskites, researchers propose intricately designed semiconducting halide (X)-ferroelectric oxide (O) bulk heterojunction (XOBHJ) perovskite solar cells. Such cells will be made up of all inorganic solid-state materials devoid of liquid electrolytes, therefore increasing the durability of the devices. Promising inorganic halide perovskites include Cs₂SnX₆ with bandgap ~1.2 to 2 eV and bandgap tunable Cs₂B'B"X₆ (B'= Ag+, Cu+; B''= Bi3+, In3+, Sb3+). And the ferroelectric oxide material includes Bi-M-O (M = Fe, Cr, Mn), i.e, either Bi₂FeCrO₆ or the composite of BiMnO₃ and BiMn₂O₅. Intricately woven composite of these two materials with halide perovskite impregnated into the mesoporous photoferroelectric oxide will be fabricated in an heterojunction form so the charge carriers generated by the former will be efficiently separated by the domain wall regions of the latter, thus yielding both high short-circuit current and high open-circuit voltage of solar cells. Photovoltaic devices, both with XOBHJ sandwiched between FTO and Au and the same with an additional hole transport layer and electron transport layer, will be fabricated, tested, and optimized to achieve solar cell efficiency of greater than 10 %. The all-inorganic and all-solid-state device is expected to yield exceptionally high stability and longevity. |