I have tried several recipes of formamidine bases perovskite from many articles to repeat the results of them. However, the performance of devices are still very poor,especically for Jsc of devices, which can only reach around 19 mA/cm2. When I partially replaced PbI2 to PbBr2 of precursor, the Jsc drop dramatically with no Voc increase. Comparing with the MAPbI3 devices I made, I think the main problem is the morphology. Is there any critical point or tips I have to be careful about ?