| AVS 62nd International Symposium & Exhibition | |
| Energy Frontiers Focus Topic | Monday Sessions |
| Session EN+AS+EM+NS+SE+SS+TF-MoA |
| Session: | Solar Cells II |
| Presenter: | Weina Peng, University of Texas at Dallas |
| Authors: | W.N. Peng, University of Texas at Dallas B.X. Anand, University of Texas at Dallas L.-H. Liu, University of Texas at Dallas S.C. Sampat, University of Texas at Dallas B.E. Bearden, University of Texas at Dallas A.V. Malko, University of Texas at Dallas Y.J. Chabal, University of Texas at Dallas |
| Correspondent: | Click to Email |
Perovskites are emerging as front-runners for solar cell applications because of their superior optoelectronic properties. Over the past few years the grain size of perovskites has been continuously improved from several hundred of nanometers to a few millimeters which resulted in better solar conversion efficiencies. In addition to surface and grain boundary related defects, perovskites are prone to the formation of bulk defects as well. However the role of bulk defects in the determination of photovoltaic performance of perovskites is rarely explored. To this end we investigate the impact of annealing temperature on the defect density in polycrystalline CH3NH3PbI3 thin films of ~1 micron average grain size prepared using vapor assisted solution process (VASP). The photoluminescence (PL) intensity and lifetime show systematic reduction when the annealing temperature is increased from 150°C to 200°C. A rough estimate of the defect state density obtained using fluence dependent PL measurements reveal a 5 fold increase in defect density for a 25°C increase in annealing temperature although the average grains size stays unchanged. Furthermore, surface passivation of perovskite films using Al2O3 via atomic layer deposition leads to an improvement in PL intensity and lifetime. But the PL quantum efficiency, as well as the lifetime, of the surface passivated 200°C annealed sample remains significantly lower than that of the un-passivated 150°C annealed sample indicating that the majority of the defects states we observe in the high temperature annealed samples originate from bulk defects. Thus the present study shows that minimizing the number of bulk defects, in addition to surface defects, is very important in the realization of highly efficient perovskite solar cells.