Here we explore the effect of the partial substitution of univalent methylammonium cations (MA) with hydrazinium ions (HA) on the stability, morphology and photovoltaic performance of hybrid MA(1−x)HAxSnI3 systems.

Trap states are well-known to plague organic photovoltaic devices and their characterization is essential for continued progress. This letter reports on both the deep trap profiles and kinetics of trap emission, studied through temperature dependent capacitance measurements. Three polymer based systems relevant to photovoltaics, namely, P3HT:PC60BM, PTB7:PC70BM, and PCDTBT:PC70BM were investigated. Each polymer showed a markedly different deep trap profile, varying in shape from a nearly constant density of states to a sharp Gaussian. In contrast, the frequency of trap emission was similar for each—ca. 108−109 Hz—indicating a universal value and similar trapping mechanisms despite the differences in energetic distribution. The latter result is important in the light of range of conflicting values reported, or higher value (1012 Hz) typically borrowed from crystalline inorganic materials.

Here, we present a systematic study of the thermal and photochemical degradation pathways for a series of complex tin-based halides ASnX 3 (X = I, Br) with organic (CH 3 NH 3 + , H 2 NCHNH 2 +) and inorganic (Cs + ) univalent A-site cations. Thin films of tin-based perovskites were exposed to continuous light soaking and/or thermal annealing in the dark under an inert atmosphere, which simulate pragmatic anoxic operation conditions of solar cells with the absorber layer isolated from the (re)action of oxygen and moisture by appropriate encapsulation. Using a set of complementary techniques such as optical spectroscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectra, we have elucidated that hybrid tin halide perovskites undergo rapid thermal and light-induced degradation with the complete elimination of organic cations and the formation of some volatile decomposition products and Sn(IV) halide species. On the contrary, allinorganic compositions comprising CsSnBr 3 and, particularly, CsSnI 3 showed a much superior thermal and photochemical stability with respect to both light and elevated temperatures. Unfortunately, all investigated complex tin halides suffer from heat-and light-induced Sn(II) disproportionation with the formation of Sn(IV) species and, presumably, metallic Sn 0 . This facile disproportionation and chemical degradation pathway reduces dramatically the intrinsic stability of Sn(II) complex halides and limits their potential for practical applications. While this problem can be addressed using additional stabilizing additives and crystal-lattice-engineering approaches, the analysis of the comprehensive sets of our results solidifies further rational design approaches for the development of lead-free absorbers for inorganic perovskite-based solar cells with enhanced stability for efficient and durable photovoltaic systems.