Bulk and Micro-Photoluminescence Studies of Perovskites

Perovskite based solar cells are the subject of intense research interest due to the attractive properties of perovskite; high carrier mobilities, large absorption coefficients, tuneable bandgaps, and long carrier diffusion lengths. One of the challenges in any solar cell design is how to get the charge carriers efficiently out of the device. To aid charge extraction, electron and hole extraction layers are routinely incorporated into the device stack.<br/><br/>One promising material being investigated as a hole extraction layer are vertically aligned carbon nanotubes (VACNTs). The VACNTs can be grown in a grid pattern of ‘towers’ atop the ITO electrode in order to achieve improved charge extraction while maintaining high optical transmission through the ITO/VACNTs. Photoluminescence response from perovskite materials is proportional to the number of charge carriers in the layer and therefore sensitive to charge extraction into adjacent layers. This makes photoluminescence based techniques invaluable for investigating the performance of new extraction layers. In this work steady-state and time-resolved confocal photoluminescence microscopy and photoluminescence quantum yield studies were used to quantify hole transfer efficiency into the VACNT towers.