Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effects

Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effect

General Considerations for Improving Photovoltage in Metal–Insulator–Semiconductor Photoanodes

Metal–insulator–semiconductor (MIS) photoelectrodes offer a simple alternative to the traditional semiconductor–liquid junction and the conventional p–n junction electrode. Highly efficient MIS photoanodes require interfacial surface passivating oxides and high workfunction metals to produce a high photovoltage. Herein, we investigate and analyze the effect of interfacial oxides and metal workfunctions on the barrier height and the photovoltage of a c-Si photoanode. We use two metal components in a bimetal contact configuration and observe the modulation of the effective barrier height and the resulting photovoltage as a function of the secondary outer metal. The photovoltage shows a strong linear dependence by increasing the inner metal workfunction, with the highest photovoltage achieved by a MIS photoanode using a platinum inner metal. We also found that coupling a thin aluminium oxide with an interfacial silicon oxide and controlling the oxide thickness can significantly improve the photovoltage of an MIS junction photoanode

Disordered polymer antireflective coating for improved perovskite photovoltaics

Light management through low index medium, such as antireflective coating (ARC) provides practical solution to improve the efficiency of photovoltaics. However, a brute-force development of photonic structure on ARC is not necessarily useful, because of random scattering associated with impediment of light transmission. Here, we leverage the concept of disorder, rather than random, structured on ARC for improving efficiency without modifying original architecture of thin-film photovoltaics. We demonstrate a disordered polymer that leads to a total reflectance of 5% while demonstrating a high transmission of 94% across 300 to 820 nm wavelength. Next, we find that the arrangement of disordered points and line arrays constructing the polymer seems to be the key to control bandwidth performance of the ARC. Finally, we apply this into Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 perovskite, and through experiments with wave-optics and full-device simulation, show a 1.6-fold absorption gain leading to 19.59% power-conversion-efficiency by the disordered ARC.Ministry of Education (MOE)National Research Foundation (NRF)Accepted versionThis work is supported by the National Research Foundation, Prime Minister’s Office, Singapore under Energy Research Innovation Program (Grant number, NRF2015EWT-EIRP003-004 and NRF-CRP14-2014-03 and Solar CRP:S18-1176-SCRP), and Ministry of Education (MOE2016‐T2‐1‐052)

Controlling spontaneous emission from perovskite nanocrystals with metal–emitter–metal nanostructures

We show the increase of the photoluminescence intensity ratio (PLR) and the emission rate enhancement of perovskite cesium lead bromide (CsPbBr3 ) and formamidinium lead bromide (FAPbBr3 ) nanocrystals (NCs) in the presence of single and double gold layer cavities, which we refer to as Metal-Emitter (ME) and Metal-Emitter-Metal (MEM) nanostructures. Up to 1.9-fold PLRs and up to 5.4-fold emission rate enhancements were obtained for FAPbBr3 NCs confined by double gold layers, which are attributed to plasmonic confinement from the gold layers. The experimentally obtained values are validated by analytical calculations and electromagnetic simulations. Such an effective method of manipulation of the spontaneous emission by simple plasmonic nanostructures can be utilized in sensing and detection applications.Ministry of Education (MOE)Published versionThis research was funded by Ministry of Education, Singapore, grant nos. MOE2016-T2-1-052 and MOE2019-T1-002-063