The presentation will focus on our recent combinatorial experiments [1], and newer not yet presented data, that show the optoelectronic quality and the stability of thousands of compositions of hybrid perovskites. We will also show the effects of vapor-treatments and methods to re-grow hybrid perovskites to improve their optoelectronic quality [2]. Hyperspectral maps of steady-state absolute intensity photoluminescence (AIPL) are used to determine the quasi-Fermi level splitting (QFLS) [3] for the combinatorial libraries. For methyl ammonium iodobromides, the QFLS upon first illumination increases with bandgap and reaches a maximum of 1.27 eV under 1 Sun illumination intensity for a bandgap of 1.75 eV. However, the optoelectronic quality, defined as the ratio of the QFLS to the maximum theoretical QFLS for bandgap, decreases with bandgap from around 88% for 1.60 eV bandgap down to 82% for 1.84 eV bandgap. We will also present new data on the QFLS for formamidinium, cesium, and other +1 cations and show how they cross-correlate with the halide composition. We will also show new data on the QFLS for some novel lead-free 3D perovskites.

We will also show the dynamic effect on QFLS that reversible light induced defects create, particularly for high bandgap hybrid perovskites and show the connection to halide vacancies. Even with the light induced defect, we show that stable QFLS of about 1.17 eV are possible. Comparing our QFLS to Voc values from HP devices reported in the literature indicates that higher open circuit voltages are possible for high bandgap perovskites but may require optimization of band alignment.

Analysis of the spectral shape of the PL emission suggests Franz-Keldysh broadening from local electric fields or from a screened Thomas-Fermi density of states (as opposed to a joint density of states due to Urbach disorder). We will also show results that reveal the local carrier temperatures in HP under steady state illumination. The presentation will also showcase recent results on the development of tandem photovoltaics with solution processed CIGS and CZTS as the bottom cells. 

[1] Braly, Hillhouse, "Optoelectronic Quality and Stability of Hybrid Perovskites from MAPbI3 to MAPbI2Br using Composition Spread Libraries," J. Phys. Chem. C 120, 893-902 (2016).

[2] Tosun, Braly, Hillhouse, "Enhanced Carrier Lifetimes of Pure Iodide Hybrid Perovskite viaVapor-Equilibrated Re-Growth (VERG)", J. Phys. Chem. Lett. 2015, 6, 2503.

[3] Katahara, Hillhouse, “Quasi-Fermi level splitting and Sub-bandgap Absorptivity from Semiconductor Photoluminescence” J. Appl. Phys. 2014, 116, 173504.