MAPbBr $_3$单晶中陷阱填充对载流子扩散的影响
Impact of Trap Filling on Carrier Diffusion in MAPbBr$_3$ Single Crystals
摘要：
我们目前的实验证据表明，有效的载流子扩散长度（$L_d$）和寿命（$τ$）依赖于在MAPbBr $_3$单晶的载流子密度。独立的测量表明，$L_d$和$τ$减少与光载流子密度的增加。扫描光电流显微镜用于提取特征光电流$I_{ph}$衰减长度参数，$L_d$，其是有效载流子扩散的量度。电子和空穴的$L_d$幅度分别为~ 13.3 $μ$ m和~ 13.8 $μ$ m。均匀光偏置的边际增加（$\leq 5 \times 10^{15}$光子/cm $^2$）增加了调制光电流幅度，并分别将电子和空穴的$L_d$参数降低了2倍和3倍，表明复合不是单分子的。的$L_d$的变化与光致发光寿命研究中的功能。寿命变化的分析表明，强度依赖的单分子和双分子复合的趋势与复合常数分别确定为约9.3 $\times 10^6$ s $^{-1}$和约1.4 $\times 10^{-9}$ cm $^{3}$ s $^{-1}$。根据$L_d$和寿命的变化趋势，推测在低强度激发区，载流子输运主要受子带隙陷阱复合的影响，而在高强度激发区，载流子输运主要受双分子复合的影响.
英文摘要：
We present experimental evidence showing that the effective carrier diffusion length ($L_d$) and lifetime ($τ$) depend on the carrier density in MAPbBr$_3$ single crystals. Independent measurements reveal that both $L_d$ and $τ$ decrease with an increase in photo-carrier density. Scanning photocurrent microscopy is used to extract the characteristic photocurrent $I_{ph}$ decay-length parameter, $L_d$, which is a measure of effective carrier diffusion. The $L_d$ magnitudes for electrons and holes were determined to be ~ 13.3 $μ$m and ~ 13.8 $μ$m respectively. A marginal increase in uniform light bias ($\leq 5 \times 10^{15}$ photons/cm$^2$) increases the modulated photocurrent magnitude and reduces the $L_d$ parameter by a factor of two and three for electrons and holes respectively, indicating that the recombination is not monomolecular. The $L_d$ variations were correlated to the features in photoluminescence lifetime studies. Analysis of lifetime variation shows intensity-dependent monomolecular and bimolecular recombination trends with recombination constants determined to be ~ 9.3 $\times 10^6$ s$^{-1}$ and ~ 1.4 $\times 10^{-9}$ cm$^{3}$s$^{-1}$ respectively. Based on the trends of $L_d$ and lifetime, it is inferred that the sub-band-gap trap recombination influences carrier transport in the low-intensity excitation regime, while bimolecular recombination and transport dominate at high intensity.
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