Normal and Inverted Hysteresis in Perovskite Solar Cells

Abstract

Hysteretic effects are investigated in perovskite solar cells in the standard FTO/TiO2/CH3NH3PbI3−xClx/spiro-OMeTAD/Au configuration.We report normal (NH) and inverted hysteresis (IH) in the J-V characteristics occurring for the same device structure, the behavior strictly depending on the pre-poling bias. NH typically appears at pre-poling biases larger than the open circuit bias, while pronounced IH occurs for negative bias pre-poling. The transition from NH to IH is marked by a intermediate mixed hysteresis behavior characterized by a crossing point in the J-V characteristics. The measured J-V characteristics are explained quantitatively by the dynamic electrical model (DEM). Furthermore, the influence of the bias scan rate on the NH/IH hysteresis is discussed based on the time evolution of the non-linear polarization. Introducing a three step measurement protocol, which includes stabilization, pre-poling and measurement, we put forward the difficulties and possible solutions for a correct PCE evaluation.

The Influence of the Relaxation Time on the Dynamic Hysteresis in Perovskite Solar Cells

“…A different situation occurs when the initial polarization is negative, P 0 < 0, and an inverted hysteresis is evidenced, i.e. the current in forward scan is larger than in reverse [5]. Assuming the same parameters of the DEM and changing only P 0 = −P ∞ , we obtain the J-V characteristics depicted in Fig.…”

“…[5], i.e. the samples are pre-poled with an initial polarization P 0 and subsequently a reverse-forward (R-F) bias scan with constant rate α = ∂V/∂t is performed.…”

“…We base our analysis on the dynamic electrical model (DEM) [4], which is able to accurately reproduce the experimental J-V characteristics. In particular, a unified picture comprising normal (NH) and inverted (IH) hysteresis in the same device structure subject to different bias pre-conditioning was recently given by DEM, validated by J-V measurements [5]. e-mail: nemnes@solid.fizica.unibuc.ro DEM provides a time dependent description of the J-V characteristics, by solving the coupled system of differential equations with given initial conditions as described in detail in Refs.…”

“…e-mail: nemnes@solid.fizica.unibuc.ro DEM provides a time dependent description of the J-V characteristics, by solving the coupled system of differential equations with given initial conditions as described in detail in Refs. [4,5]:…”

Tunable hysteresis effect for perovskite solar cells

“…In general, 'normal' hysteresis is the case where there occurs a large loss of photocurrent and fill factor (FF) during the reverse to forward voltage (R-F) scan, (also leading to a reduced open-circuit voltage, V OC ) as compared to the forward to reverse (F-R) scan. 14 Inverted hysteresis has been observed as a reduction in the short-circuit current (J SC ) for F-R scans compared to R-F scans by Shen et al 17 and Nemnes et al 18 while Tress et al 19 observed a loss in the FF in the form of an S-shaped kink for the F-R scan. Both normal and inverted hysteresis trends have been observed to become more acute for faster scans.…”