Alternative benzodithiophene (BDT) based polymeric hole transport layer for efficient perovskite solar cells

Organic-inorganic perovskite cell has shown a great deal of interest in past few years due to its ability to achieve high power conversion efficiency (PCE). Use of charge transport layers such as n-type TiO2 and p-type doped spiroOMeTAD in a n-i-p device architecture has shown enhanced perovskite solar cell device performance. Use of doped spiroOMeTAD as hole transport layer in the n-i-p device structure has been effective but possess disadvantages such as complex processing, use of corrosive additives, processing in ambient air for efficient hole doping. Here we report the study of solution processed benzodithiophene based polymer PBDTT-FTTE as an alternative hole transport layer to doped small molecule spiroOMeTAD. PBDT-FTTE doped with 3% DIO (diiodooctane) achieved PCE of 11.6% which was comparable to matching PCE of 11.6% obtained from using spiroOMeTAD as hole transport layer. We showed that unlike spiroOMeTAD, polymer PBDIT-FTTE is processed inside NZ filled glove box and is easier to process as compared to spiroOMeTAD which requires processing in ambient humid air and is doped with additives mixed in corrosive solvent, causing degradation to perovskite layer underneath.