Effects of π-conjugation on electrochemical properties within hole-transporting materials for perovskite solar cells from first principle and molecular dynamics

Abstract The luck of low cost and highly efficient HTMs is one challenge for perovskite solar cells toward future commercialization. Inspired by two important HTMs ( CBP and 2TPA-2-DP See Scheme 1), three new organic molecules, CBP-OD , CBP-2OD , and CBP-3OD (See Scheme 1) are theoretically designed and their structure-property relationship is studied by the first principle and molecular dynamics associated with the Marcus theory and Einstein-Smoluchowski relation (See Eq. (1)). The HOMO energy level of designed three molecules is lower than that of 2TPA-2-DP but higher than that of CBP . Moreover, their reorganization energies are all larger than that of CBP and 2TPA-2-DP , which is not favorable to be HTMs. However, they have the smaller exciton binding energies, which is beneficial for the separation of hole and electron. Although reorganization energies of three designed molecules are similar, CBP-OD has the largest hole mobility because of the larger transfer integral, which is even larger than that of CBP indicating a superior potential to be HTM candidate. On the contrary, hole mobilities of CBP-2OD and CBP-3OD are similar or less than that of CBP . Additionally, all of designed molecules have the much larger hole mobility than 2TPA-2-DP . The influence of the packing model and the elongation of π-conjugation on the hole mobility is importantly discussed.