Comparative studies of optoelectrical properties of prominent PV materials: Halide perovskite, CdTe, and GaAs

Abstract

Note: in this version the excitation densities were computed using measured laser profiles instead of those calculated using the diffraction limited formula. AbstractWe compare three representative high performance PV materials: halide perovskite MAPbI3, CdTe, and GaAs, in terms of photoluminescence (PL) efficiency, PL lineshape, carrier diffusion, and surface recombination, over multiple orders of photo-excitation density. An analytic model is used to describe the excitation density dependence of PL intensity and extract the internal PL efficiency and multiple pertinent recombination parameters. A PL imaging technique is used to obtain carrier diffusion length without using a PL quencher, thus, free of unintended influence beyond pure diffusion. Our results show that perovskite samples tend to exhibit lower Shockley-Read-Hall (SRH) recombination rate in both bulk and surface, thus higher PL efficiency than the inorganic counterparts, particularly under low excitation density, even with no or preliminary surface passivation. PL lineshape and diffusion analysis indicate that there is considerable structural disordering in the perovskite materials, and thus photo-generated carriers are not in global thermal equilibrium, which in turn suppresses the nonradiative recombination. This study suggests that relatively low point-defect density, less detrimental surface recombination, and moderate structural disordering contribute to the high PV efficiency in the perovskite. This comparative photovoltaics study provides more insights into the fundamental material science and the search for optimal device designs by learning from different technologies.

Revealing the internal luminescence quantum efficiency of perovskite films via accurate quantification of photon recycling

“…As expected for perovskite films with a very low trap density, Q lum e and the corresponding Q lum i of the 260 (160) nm-thick MAPI film increase only slightly from a remarkable $33.8% ($30.6%) and $66.8% (61.1%) at low intensities of $0.1 Sun up to $52.2% ($46.6%) and $81.4% ($75.6%) at higher intensities of $3 Sun (see Figure S23), respectively. 11,15,30,79 Despite the very high p e , our analysis reveals that photon recycling still accounts for an impressive a PR =a tot $58% of the total emission for the 260 nm-thick MAPI film (see upper panels in Figure 3C; $52% and $32% for the 160 nm-and 80 nmthick films, respectively) which is comparable with values recently simulated for the best state-of-the-art PeLEDs. 33 In addition, our curve-fitting model also for the first time allows estimation of values for p eÀd of perovskite films, and, interestingly, it strongly increases from 6.0% G 0.5% to 17.4% G 0.7% with decreasing film thickness, which we attribute to the suppression of waveguide modes resulting in a larger fraction of direct emission.…”

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

“…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.…”

Carrier Dynamics and Evaluation of Lasing Actions in Halide Perovskites

“…However, when P increases, the second-order term (bn 2 ) becomes comparable with the first-order term (an), resulting in the nonlinear relationship between P and n ( Figure 3B). Therefore, the linear nature of logarithmic power-dependent PL plots is typically lost at higher CW excitation intensities [57]. Since monomolecular and bimolecular recombination processes dominate at different carrier density regions, the PL quantum efficiency (PLQE) of perovskites with monomolecular radiative recombination behaves differently compared with those with bimolecular radiative recombination.…”