Wolff, C.M.; Bourelle, J.; Phoung, L.Q.; Kurpiers, J.; Feldmann, S.; Caprioglio, P.; Marquez, J.A.; Wolansky, J.; Unold, T.; Stolterfoht, M.; Shoaee, S.; Deschler, F.; Neher, D.: Orders of Recombination in Complete Perovskite Solar Cells – Linking Time-Resolved and Steady-State Measurements. Advanced Energy Materials 11 (2021), p. 2101823/1-10
10.1002/aenm.202101823
Open Access Version
Abstract:
Ideally, the charge carrier lifetime in a solar cell is limited by the radiative free carrier recombination in the absorber which is a second-order process. Yet, real-life cells suffer from severe nonradiative recombination in the bulk of the absorber, at interfaces, or within other functional layers. Here, the dynamics of photogenerated charge carriers are probed directly in pin-type mixed halide perovskite solar cells with an efficiency >20%, using time-resolved optical absorption spectroscopy and optoelectronic techniques. The charge carrier dynamics is found to be in complete device to be fully consistent with a superposition of first-, second-, and third-order recombination processes, with no admixture by a non-integer order recombination pathways Under solar illumination, recombination in the studied high-efficiency solar cells proceeds predominantly through nonradiative first-order recombination with a lifetime of 250 ns, which competes with second-order free charge recombination which is mostly if not entirely radiative. Results from the transient experiments are further employed to successfully explain the steady state solar cells properties over a wide range of illumination intensities. It is concluded that improving carrier lifetimes to >3 µs will take perovskite devices into the radiative regime, where their performance will benefit from photon-recycling.