Excited State Dynamics Of Antimony Sulfide And Perovskite

Achieving high conversion efficiency of photoelectric devices has much importance on substantial energy development.Here in this paper,we introduced two different semiconductor materials—antimony sulfide(Sb2S3)and organic-inorganic hybrid perovskite.Through their steady spectra and carrier dynamics under continuous and pulse light excitations,we might draw a relative distinct physical picture of transportation and transfer of photo-generated charges in the materials and structures.This provides fundamental knowledge for fabricating more efficient photoelectric devices in the future.The main contents contain:1.Steady photoluminescence(PL)and transient spectroscopy were utilized to study optical properties of antimony sulfide single crystal and thin films grown by different methods.For the first time,we discovered the existence of intrinsic defects in Sb2S3.Photo-induced free electrons and holes were rapidly trapped by these defects and formed self-trap excitons(STE).PL of STE had a large stokes shift compared to its optical gap.That's why open circuit voltage of Sb2S3 solar cells is much lower than perovskite,which has the same optical gap.It also has much importance on fundamental knowledge of this kind of materials.2.We prepared qusi-2D multi-quantum-well(MQW)perovskite thin film by spin-casting method.The ratio of BAI(PEAI or PBAI),CsI and Pbl2 was 0.83:0.92:1.Multi-peaks at different wavelengths in absorption and PL spectra proved that different thickness perovskite quantum wells(n=2-7)together formed a MQW system.The bleach kinetics of transient absorption spectroscopy indicated fast energy and slow charge transferred from small n to large n quantum wells at?0.5ps and 10-30ps time constant respectively.Intriguingly,changing different length chain amine had rare effects orn these two transfer process and transfer rate was even slightly fast when using PBA as organic ligand.From structure characterization,we found the ratio of thick perovskite QW was larger than thin QWs and the thick QWs preferred to grow perpendicular to substrate rather than thin QWs lying parallel.As a result,we speculated the stacking modes of perovskite QWs in thin film changed from lying parallel to perpendicular as the length of organic amine ligand becoming longer,therefore,the energy and electron transfer process had no dependence on distance between multi-quantum wells.