Quantitative Correlation of Perovskite Film Morphology to Light Emitting Diodes Efficiency Parameters

This paper reports quantitative correlation of CH3NH3PbBr3 (MAPbBr3) thin film morphology to light emitting diode efficiency parameters. Sequential (spin coating) deposition is used for highly reproducible and dense film morphology of MAPbBr3 thin-film. In this fabrication process using an orthogonal solvent approach, control of morphology, coverage, thickness, and optical properties in these compact thin-films is demonstrated. Optical studies show direct correlation between morphology to dynamics of photoluminescence (PL) and absolute PL yield. Perovskite light emitting diodes (PeLEDs) are fabricated from these films to find the best ratio of PbBr2 versus MABr for optimal performance. This study demonstrates PeLEDs with high brightness, ≈1050 cd m−2 at 4.7 V (luminance efficiency ≈0.1 cd A−1), for optimal thin-film process with state-of-the-art device performance. This quantitative analysis suggests that these state-of-the-art PeLEDs suffer from poor charge carrier balance (≈2%) and out-coupling efficiency (≈6%). Interestingly, charge carrier balance and PL yield together can explain the change in PeLED efficiency modulation with film morphology. Studies on single carrier devices show that these PeLEDs are electron current dominated and charge carrier balance increases with operating bias voltage.