The application of mesoporous materials in perovskite solar cells allows the perovskite absorber to adhere to the mesoporous metal oxide framework for the purposes of increasing the light-receiving area of the photosensitive material and improving the efficiency of the device. A typical mesoporous solar cell consists of a FTO electrode, a dense electron transport layer, a mesoporous oxide layer, a perovskite layer, a hole transport layer, and an electrode layer. TiO2 is the most typical mesoporous framework material, which allows the perovskite nanocrystals to penetrate into the pores of mesoporous TiO2 by solution spin-coating and forms an interconnected absorbing layer. The main difference from the mesoscopic structure is that the planar structure removes the porous metal oxide framework. Two interfaces are formed between the perovskite materials and the two layers (the electron transport layer and the hole transport layer). Therefore, the electron-hole pairs are separated rapidly and effectively by the electron transport layer and hole transport layer, respectively. The studies on perovskite solar cells with a planar heterojunction structure contribute to the understanding of the mechanisms of light absorption and electron-hole separation and enhance the flexibility of device optimization for the development of highly efficient laminated perovskite solar cells.

Source : Article Perovskite-Based Solar Cells: Materials, Methods, and Future...

Thank you Mr Singh for your insightful answer. Will surely read the links and references you have sent, for better understanding.

Thank you.

Interested

Shrikant,

I will not repeat what has been brought by Chandra. I want to add to his answers the following point:

The use of porous TO2 as a scaffold to carry the active layer was originally sought for the material having short excitons diffusion lengths while adjusting the thickness of the porous layer for absorbing the incident solar radiation which is in the order of few of 100s of nano meters allowing short path for the exciton diffusion to the interface with transport layer.

The perovskite has a relatively high dielectric constant such that the exciton energy is small and they can dissociate thermally building free electrons and holes. So, it is the diffusion length of electrons and holes that collection thickness rather than the diffusion length of the excitons. It is found the diffusion lenth of the electron hole pairs in the perovkite is normally greater than the its absorption thickness.

So, one can say perovskite behaves as metallic semiconductors allowing the use of planar ETL and the HTL and therefore easier manufacturing process.

In fact, the advanced structure of the perovskite solar ells are planar type.

Best wishes

THank you Mr Zekry.