CH₃NH₃PbI₃/poly-3-hexylthiophen perovskite mesoscopic solar cells: Performance enhancement by Li-assisted hole conduction

To address if the non-triphenylamine derivative hole transporting materials such as P3HT (poly-3-hexylthiophene) could also exhibit high device efficiency in mesoscopic MAPbI₃ perovskite solar cells, we examined the effect of Li-TFSI (Li-bis(trifluoromethanesulfonyl) imide) and t-BP (4-tert-butylpyridine) additives added in P3HT on device performance. Unlike the triphenylamine HTMs, the P3HT thiophene HTM without amine moiety was not doped by the additives but its conductivity was significantly improved by the Li-TFSI/t-BP mediated additional hole conduction. By inclusion of Li-TFSI/t-BP additive, we could fabricate more efficient mesoscopic MAPbI₃ perovskite solar cells with smaller hysteresis with respect to scan direction due to Li mediated additional hole conduction.