P3CPenT as an organic hole transport layer for perovskite solar cells

Perovskite solar cells (PSC) are the third-generation solar cells, which have a low production cost and have achieved similar laboratory scale efficiencies as the first-generation silicon solar cells. In the present work, we performed density functional theory calculations on the organic material, poly[3-(5-carboxypentyl) thiophene-2,5-diyl] regioregular (P3CPenT). The ground state and excited state properties of P3CPenT are calculated. The HOMO-LUMO levels and electronic bandgap obtained from the calculations are compared with the experimental values for validation of the theory. A high electron reorganization energy and low hole reorganization energy ensures that P3CPenT aids the flow of holes and hinders the flow of electrons. The optical bandgap and low exciton binding energy indicates its potential as a hole transport layer (HTL). The ease of fabrication of P3CPenT is established by showing that the oligomer is soluble in dimethyl sulfoxide (DMSO), which is the most commonly utilized solvent for the fabrication of PSCs. The hydrophobic nature of P3CPenT as established by the present work shows that it is stable with moisture and would thus protect the underlying MAPbI(3) perovskite layer from decomposing and hence improve its lifetime and stability. Fill factor (FF) of 78.07% and a power conversion efficiency (PCE) of 14.88% has been obtained for PSC with P3CPenT HTL.