Characterization of trap states in perovskite films by simultaneous fitting of steady-state and transient photoluminescence measurements

Abstract

Understanding carrier recombination mechanisms and quantifying recombination dynamics are key to improving the performance of state-of-the-art perovskite solar cells. Here, we present a method to quantify the quality of perovskite thin films using a combination of steady-state and transient photoluminescence measurements. The combined experimental datasets are fitted using a single, general recombination model, from which detailed trap and recombination parameters can be extracted, and the accuracy of the fitted values is estimated. This approach expands the application of photoluminescence measurements to include quantitative evaluation of the most relevant defect characteristics, including trap density, energy level, and carrier capture coefficients. We apply this approach to compare perovskite films of the widely studied methyl-ammonium lead iodide (MAPbI 3) with the high performance quadruple-cation, mixed-halide composition Cs 0.07 Rb 0.03 (FA 0.85 MA 0.15) 0.9 Pb(I 0.85 Br 0.15) 3. Our quantitative analysis of trap properties in these perovskite films suggests that the superior performance of the quadruple cation films may be due to a greatly reduced electron capture coefficient, rather than a significant reduction in the trap density.

Are Shockley-Read-Hall and ABC models valid for lead halide perovskites?

“…While the importance of distinguishing between the single pulse and quasi-CW regimes has been noted in several publications before, 9,33 it has never been accomplished for MHPs experimentally. Indeed, in none of the published works presenting theoretical fits of experimental PLQY(W) dependencies this determination was possible simply because either only CW excitation 14,43 or pulse excitation with only one (625 kHz 17 , 1 kHz 33 ) or two (20 MHz and 250 kHz) 16 repetition rates of the laser pulses were employed.…”

“…1 , 2 The emergence of novel semiconductors like metal halide perovskites exhibiting intriguing and often unexpected electronic properties, [3][4][5][6][7][8][9][10] triggered a renewed interest in revisiting the classical textbook theories of charge recombination and the development of more complete, accurate models. [11][12][13][14][15][16][17] Moreover, modern technical advances in experimental and computational capabilities 4,[18][19][20][21] allow for a detailed quantitative comparison between experiment and theory, far beyond what was once possible.…”

“…15 and references there in) with fewer reports employing SRH or its modifications. 13,14,16,17,33,38,43 The ABC and SRH kinetic models are typically employed to describe experimentally acquired data such as the excitation power density dependence of PL quantum yield (PLQY) measured upon continues wave (CW) or pulsed excitation, time-resolved PL decay kinetics and kinetics of the transient absorption signal. These models are applied to semi-quantitatively explain the experimental results and extract different rate constants, [13][14][15]20,[33][34][35][36]44,45 often without necessarily considering the models' limitations.…”

“…These models are applied to semi-quantitatively explain the experimental results and extract different rate constants, [13][14][15]20,[33][34][35][36]44,45 often without necessarily considering the models' limitations. Despite the very large number of published studies describing electronic processes in MHPs using the terminology of classical semiconductor physics to the best of our knowledge, there have been only very few attempts to fit both PL decay and PLQY dependencies of excitation power using ABC/SRH-based models, 14,16,17,33 These attempts, however, were of limited success because large discrepancies between the experimental results and the theoretical fits were often permitted.…”

“…The pulse fluence was set one of the five values defined by the filters set placed in the laser beam: P1=4.1x108 , P2=4.9x109 , P3=5.1x1010 , P4=5.5x1011 and P5=4.9x1012 photons/cm 2 . In the single pulse regime these pulses create charge carrier densities of approximately 1.04x1013 , 1.24x1014 , 1.3x1015 , 1.37x1016 , 1.24x1017 cm-3 respectively. (a) PLQY(f,P) map for MAPbI3 film grown on glass (G/MAPI) with the single pulse and quasi-CW excitation regimes indicated.…”