Abstract
This study demonstrates the formation of extremely smooth and uniform formamidinium lead bromide (CH(NH2)(2)PbBr3 = FAPbBr(3)) films using an optimum mixture of dimethyl sulfoxide and N,N-dimethylformamide solvents. Surface morphology and phase purity of the FAPbBr(3) films are thoroughly examined by field emission scanning electron microscopy and powder X-ray diffraction, respectively. To unravel the photophysical properties of these films, systematic investigation based on time-integrated and time-dependent photoluminescence studies are carried out which, respectively, bring out relatively lower nonradiative recombination rates and long lasting photogenerated charge carriers in FAPbBr(3) perovskite films. The devices based on FTO/TiO2/FAPbBr(3)/spiro-OMeTAD/Au show highly reproducible open-circuit voltage (V-oc) of 1.42 V, a record for FAPbBr(3)-based perovskite solar cells. V-oc as a function of illumination intensity indicates that the contacts are very selective and higher V-oc values are expected to be achieved when the quality of the FAPbBr(3) film is further improved. Overall, the devices based on these films reveal appreciable power conversion efficiency of 7% under standard illumination conditions with negligible hysteresis. Finally, the amplified spontaneous emission (ASE) behavior explored in a cavity-free configuration for FAPbBr(3) perovskite films shows a sharp ASE threshold at a fluence of 190 mu J cm(-2) with high quantum efficiency further confirming the high quality of the films.