Hot Carrier Dynamics in Operational Metal Halide Perovskite Solar Cells
One of the main approaches to inhibit carrier cooling in semiconductor systems enabling the study of hot carrier solar cell protocols is the use of concentrated illumination to obtain high power densities and create a phonon bottleneck. This, however, typically also increases the lattice temperature of the solar cells significantly. Accordingly, the solar cells subject to high concentration illumination also need to withstand high operating temperatures. Having previously demonstrated the high temperature tolerance of the triple halide perovskite (FA0.8Cs0.2Pb1.02I2.4Br0.6Cl0.02) solar cells, here the hot carrier relaxation dynamics are studied in these devices using high power transient absorption (TA) measurements. In addition to monitoring TA spectra obtained at different time delays, the thermalization mechanisms of hot carriers is mapped with power dependent TA to extract the carrier cooling time in this system under in-operando conditions at various bias conditions that reflect the Jsc, Vmax and Voc of these structures, and subsequently deconvolve the underlying physics of carrier relaxation; as well as track the dynamics of the thermalization close to working conditions of the solar cells. These measurements uncover a complex interaction of hot carrier thermalization involving the temporal carrier density, transport, and extraction, and apparent non-equivalent contributions with respect to non-equilibrium photogenerated electrons and holes in these metal halide perovskite solar cell architectures.