Metal halide perovskites (MHPs) have inherent properties that show strong potential for light emission-based optoelectronic applications. MHPs typically employ an ABX3 crystal structure where A is an organic, inorganic, or hybrid cation, B is typically lead or tin, and X is a halide anion. 

By introducing dopants into the B-site, one can improve the MHPs' optoelectronic properties, which can result into higher performance devices. 

I have investigated the introduction of transition metal dopants (e.g., Mn2+, Ni2+, Zn2+, etc.) into the MHPs' B-site and their effects on perovskite LED performance. For instance, in our JACS paper we looked at the effects of transition metal dopants on MHP nanocrystals at device relevant conditions. We showed both theoretically and experimentally how the  lattice periodicity breaking effect primarily enhances the radiative rates in doped MHP nanocrystals.

Zooming in on the effects of Mn2+on perovskite LEDs, I engineered Mn2+ doped perovskite LEDs and studied their performance with respect to external quantum efficiency and operational stability. In our Device paper, by introducing a molecular additive known as tris(4-fluorophenyl)phosphine oxide (TFPPO), we were able to simultaneously achieve incredibly bright and efficient transition metal doped LEDs. However, we also found that the operational stability of these LEDs is degraded with higher concentrations of TFPPO. We studied this efficiency-stability trade-off with optoelectronic and photophysical characterization on the Mn2+ doped perovskite LEDs and found that while TFPPO treatment does initially improve LED performance, this enhancement is not resilient under identical device operating conditions. This implies that before phosphine oxide additives are universally adopted in perovskite LEDs, their stability degradation mechanisms must be further investigated.

Today, most perovskite LEDs are fabricated using spin-coating techniques for the solution-based deposition of the perovskite active layer. While these techniques have led to rapid progress in achieving high external quantum efficiencies(EQEs) in perovskite LEDs (within the last decade, >20% EQEs have been achieved for red and green perovskite LEDs), spin-coating based fabrication of perovskite LEDs limits their commercial viability. This is largely due to the large sample-sample variability and substrate area limitations incurred by spin-coating. On the other hand, other LEDs such as organic LEDs (OLEDs), are fabricated using vacuum thermal evaporation techniques.

Vacuum thermal evaporation (VTE) holds the potential to reduce perovskite LED variability, increase pixel resolution by using precise metal masks, and enable cleaner production since no harmful solvents are needed. VTE involves heating perovskite precursor materials to form gaseous molecules that then interact with each other on the LED substrate surface to form a perovskite active layer. This process involves careful optimization of the nucleus formation, stoichiometric ratio of precursors, and regulation of evaporation rates to result in efficient vacuum-evaporated perovskite LEDs.

I am interested in optimizing the performance of vacuum-evaporated perovskite LEDs to the levels achieved in solution-processed perovskite LEDs by studying the formation of the vacuum-evaporated perovskite layer, incorporating various additives and precursors to yield highly emissive active layers, and engineering new device architectures that promote efficient charge carrier transport within vacuum-evaporated perovskite LEDs.

Silver organochalcogenolates are an emerging class of low-dimenstional semiconductors. This class of semiconductor is similar to 2D perovskites in the sense that that they are formed in 3D crystals with 2D layers held together by interlaying van der Waals forces. However, owing to the covalent bonding between organic and inorganic constituents, these semiconductors are chemically stable in air and solvents, which is difficult to achieve in perovskites. 

In collaboration with the Tisdale Lab at MIT, we are working towards pioneering silver organochalcogenolate LEDs (SOLEDs). By designing device architectures that can effectively inject charge carriers into the active layer while also maintaining the integrity of the silver organochalcogenolate layer formation on various underlayers, we hope to debut SOLEDs as another candidate for next-generation light emission.