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Stoichiometry-controllable optical defects in CuxIn2−xSy quantum dots for energy harvesting
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-06-10 , DOI: 10.1039/d0ta03954c Addis S. Fuhr 1, 2, 3, 4, 5 , Anastassia N. Alexandrova 2, 3, 4, 6, 7 , Philippe Sautet 1, 2, 3, 4, 6
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-06-10 , DOI: 10.1039/d0ta03954c Addis S. Fuhr 1, 2, 3, 4, 5 , Anastassia N. Alexandrova 2, 3, 4, 6, 7 , Philippe Sautet 1, 2, 3, 4, 6
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The large Stokes shift for CuxIn2−xSy (CIS) quantum dots (QDs) reduces reabsorption losses in luminescent solar concentrators (LSCs). However, reabsorption still occurs due to their broad absorption spectra, which, along with below unity quantum yields, hamper device performance. The origin of these optical properties is heavily debated, and makes it difficult to optimize CIS for LSCs and other energy harvesting devices such as solid-state and sensitized solar cells. Here, we show with density functional theory calculations that anti-site defects 
form in near-stoichiometric CIS QDs, while copper vacancies charge-compensated by the oxidation of a second Cu atom 
form in Cu-deficient structures. Both defects lead to large Stokes shifts, but 
defects only localize holes in the excited-state leading to strong intragap absorption, which is suppressed for paramagnetic 
defects that localize holes in the ground-state. The relative concentration of each defect and competing defect phases that lead to non-emissive carrier trapping is controllable by stoichiometry and Fermi-level, and optimal chemical processing conditions for energy harvesting applications are discussed.
中文翻译：
用于能量收集的CuxIn2-xSy量子点中的化学计量可控的光学缺陷
Cu x In 2- x S y（CIS）量子点（QDs）的大斯托克斯位移降低了发光太阳能聚光器（LSCs）的重吸收损耗。然而，由于其宽的吸收光谱，再吸收仍然发生，这与低于统一的量子产率一起阻碍了器件的性能。这些光学特性的起源受到了广泛的争论，因此很难为LSC和其他能量收集设备（如固态和敏化太阳能电池）优化CIS。在这里，我们用密度泛函理论计算表明，在接近化学计量的CIS QD中形成了反位缺陷，而铜空位通过第二个Cu原子的氧化进行电荷补偿铜缺乏结构中形成。两种缺陷都会导致较大的斯托克斯位移，但是缺陷只会在激发态中定位空穴，从而导致强烈的内部间隙吸收，而对于在基态中定位空穴的顺磁缺陷，这种现象会受到抑制。可通过化学计量和费米能级控制导致非发射性载流子俘获的每个缺陷和竞争缺陷相的相对浓度，并讨论了能量收集应用的最佳化学处理条件。
更新日期：2020-06-30
form in near-stoichiometric CIS QDs, while copper vacancies charge-compensated by the oxidation of a second Cu atom form in Cu-deficient structures. Both defects lead to large Stokes shifts, but defects only localize holes in the excited-state leading to strong intragap absorption, which is suppressed for paramagnetic defects that localize holes in the ground-state. The relative concentration of each defect and competing defect phases that lead to non-emissive carrier trapping is controllable by stoichiometry and Fermi-level, and optimal chemical processing conditions for energy harvesting applications are discussed.
中文翻译：
用于能量收集的CuxIn2-xSy量子点中的化学计量可控的光学缺陷
Cu x In 2- x S y（CIS）量子点（QDs）的大斯托克斯位移降低了发光太阳能聚光器（LSCs）的重吸收损耗。然而，由于其宽的吸收光谱，再吸收仍然发生，这与低于统一的量子产率一起阻碍了器件的性能。这些光学特性的起源受到了广泛的争论，因此很难为LSC和其他能量收集设备（如固态和敏化太阳能电池）优化CIS。在这里，我们用密度泛函理论计算表明，
在接近化学计量的CIS QD中形成了反位缺陷，而铜空位通过第二个Cu原子的氧化进行电荷补偿铜缺乏结构中形成。两种缺陷都会导致较大的斯托克斯位移，但是缺陷只会在激发态中定位空穴，从而导致强烈的内部间隙吸收，而对于在基态中定位空穴的顺磁缺陷，这种现象会受到抑制。可通过化学计量和费米能级控制导致非发射性载流子俘获的每个缺陷和竞争缺陷相的相对浓度，并讨论了能量收集应用的最佳化学处理条件。
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