Smallest Organic Spacers-Based Ruddlesden–Popper and Dion–Jacobson Perovskites: Which One Is Better for Optoelectronics?

In this work, the smallest and analogous organic spacers “ethylammonium” (EA) and “ethylenediammonium” (EDA) are incorporated in MAPbI3 to form RP-EA and DJ-EDA perovskites (n = 1–4), respectively, in order to compare their structural, morphological, optical, and optoelectronic properties, which revealed significantly different characteristics of both perovskite phases. Effective high frequency dielectric constants (εeff) of RP-EA and DJ-EDA are correlated with their optical properties, which show that the large difference between the εeff’s of DJ-EDA (9.62; n = 1 to 7.58; n = 4) and MAPbI3 (6.5) is responsible for sharp exciton absorbance peaks in DJ-EDA perovskites. Compared to RP-EA, the DJ-EDA perovskites showed improved stability and a higher photoresponsivity of ∼1.00 mA/W (n = 4) and retained 97.67% (n = 2) of the initial photocurrent after 50 cycles of transient photocurrent under 1 sun illumination (100 mW/cm2) performed under ambient atmosphere conditions owing to their van der Waals gap free structure. On the other hand, RP-EA perovskites possess relatively fast response times which are attributed to better band alignment and in-plane morphology. Our results provide fundamental insights about the structural and photophysical properties of the smallest carbon chain organic spacer-based RP and DJ perovskites, and these findings are crucial in order to find a suitable replacement of bulk perovskites for commercial PV applications.